JP2012500474A - Photocells with processed surfaces and related applications - Google Patents

Abstract

Photovoltaic cells and processes are provided that mitigate recombination loss of photogenerated carriers. In order to reduce recombination loss, the diffusion doped layer of the active photovoltaic (PV) device is coated with a pattern of dielectric material that reduces the contact between the metal contact and the active PV device. A variety of patterns can be utilized, and one or more surfaces of the PV element can be coated with one or more dielectrics. Vertical multi-junction photovoltaic cells can be made with patterned PV elements or unit cells. Patterned PV elements can increase the series resistance of a VMJ photovoltaic cell, and patterning one or more surfaces of a PV element makes the process used to make a VMJ photovoltaic cell more complex, If the carrier loss of the diffusion doping layer of the PV element is reduced, the efficiency of the photovoltaic cell is improved.
[Selection] Figure 24

Description

Priority claim

  This application is filed on August 15, 2008, filed “SOLAR,” claiming priority from US patent application Ser. No. 12 / 535,952, entitled “PHOTOVOLTAIC CELL WITH PATTERNED CONTACTS”, filed Aug. 5, 2009. US Provisional Application No. 61 / 089,389 entitled “CELL WITH PATTERNED CONTACTS”, US Provisional Patent Application No. 61 / No. 12 / 536,982, filed August 14, 2008, entitled “VERTICAL MULTI JUNCTION CELL WITH TEXTURED SURFACE”, filed Aug. 6, 2009, claiming priority of No. 088,921 “PHOTOVOLTAIC CELL WITH BUFFER ZONE” filed on August 6, 2009 claiming priority from US Provisional Patent Application No. 61 / 088,936 entitled “SOLAR CELL WITH BUFFER ZONE” No. 12 / 536,987 titled US Patent Provisional Application No. 61 / 092,531 entitled “ELECTROLYSIS VIA VERTICAL MULTI-JUNCTION SOLAR CELL” filed Aug. 28, 2008 Claims the benefit of US patent application Ser. No. 12 / 536,992, entitled “ELECTROLYSIS VIA VERTICAL MULTI-JUNCTION PHOTOVOLTAIC CELL”, filed Aug. 6, 2009. The entire application referenced above is hereby incorporated by reference.

  The limits and increasing demand for fossil energy resources and the associated global environmental destruction are driving a global effort to diversify the various energy resources and related technologies. One such resource is solar energy that uses photovoltaic (PV) technology that converts light into electricity. Solar energy can also be utilized for heat generation (eg, in solar furnaces, steam generators, etc.). Solar technology is typically implemented with a series of PV cells or solar cells or panels thereof that receive sunlight and convert it to electricity, which can then be delivered to the power grid. Significant progress has been made in the design and manufacture of solar panels, effectively improving efficiency while reducing the cost of manufacturing solar panels. Solar panels used to provide a competitive renewable alternative energy to declining non-renewable sources where the size of the battery shrinks as more efficient solar cells are developed and the demand is large The reality of is increasing. For this purpose, a solar energy collection system, such as a solar concentrator, can be arranged to convert solar energy into electricity that can be delivered to the power grid and also collect heat. In addition to the development of solar concentrator technology, development of solar cells intended for use in solar concentrators is also underway.

  High-intensity solar cell technology, called vertical multi-junction (VMJ) solar cells, is an array of small, vertically-junction unit cells that are edge-illuminated and connected in series, with electrical connections at both ends. It has a contact. This unique VMJ battery structure inherently provides high voltage and low series resistance output characteristics and is ideally suited for efficient performance in high intensity photovoltaic concentrators. Another important feature of the VMJ battery is its simplicity of design that reduces manufacturing costs.

The effectiveness of the VMJ is obtained at 25 volts and an output power density of 400 obtained with an experimental VMJ cell with 40 series-connected junctions ranging from 100 to 2500 suns intensities. Can be demonstrated by performance data with efficiencies approaching 20% above 1,000 watts / m ² . It should be understood that the aforementioned performance in VMJ solar cells is achieved with reduced manufacturing costs and low manufacturing complexity. In this manner, the photovoltaic concentrator system is significantly feasible technically necessary to be more cost-effective and more feasible in solving global energy problems. It is considered to be an essential driving force for performance and economic efficiency. In addition, any increase in battery efficiency (eg, higher wattage in output) will directly reduce the size of the concentrator system (eg, reduce costs associated with material costs), resulting in a dollar / watt photovoltaic cost. Is reduced.

  While traditional fossil fuel costs are soaring, global energy demand is steadily increasing not only in emerging countries but also in developed countries, so the reduction in dollar / watt costs is due to the adoption of solar cell technology and Note that it is substantially related to market penetration. There is also growing concern over all related issues such as widespread environmental pollution, global warming, and national security and economic hazards associated with dependence on foreign fuel supplies. These environmental, economic and safety factors that are considered in conjunction with increasing social awareness are driving a keen interest in finding more cost-effective and environmentally friendly renewable energy solutions. Of all available renewable energy resources, solar energy has virtually the greatest potential to meet demand in an efficient and sustainable manner. In fact, the Earth receives more energy every few minutes in the form of sunlight than humans can consume over a year from virtually all other resources.

  Even if solar power is widely recognized as an ideal renewable energy technology, its associated costs can be a major obstacle to adoption and market penetration. Photovoltaic-based power is well-developed and adopted among consumers prior to adoption and gaining market share, and traditional power sources including coal-fired power that are substantially cost-effective It is necessary to gain price competitiveness. In addition, the use of low cost power is considered essential in all world economies, which may require terawatt (eg, thousands of gigawatts) solar power systems. Market research shows that installed photovoltaic systems need to be reduced to a standard cost of $ 3 / watt or less in order to be cost competitive without subsidies in large-scale practical applications. Since the cost of the installed photovoltaic system currently exceeds $ 6 / watt, considerable cost improvements are still needed.

  Over the past decades, attempts to achieve cheaper dollar / watt performance have been the primary objective of most research and development in photovoltaic technology. Despite the industry spending billions of dollars on pursuing various technologies to make it more cost effective, the existing photovoltaic industry is still selling. It requires substantial subsidies to support, and this can be an indicator of unfavorable conditions with respect to market development and industrial development.

  Currently, silicon solar cells, which remain substantially the same as originally discovered and developed in the 1960s, account for about 93% of the photovoltaic market. The existing photovoltaic industry relies heavily on the availability of low-cost scrap grade semiconductor silicon in cost-saving efforts to produce conventional solar cells. Such scrap-grade silicon, often referred to as solar-grade silicon, is inherently rejected by semiconductor device manufacturers who need the top and back of the ingot left from wafer manufacturing, as well as higher quality top grade silicon wafers. Note that it is a non-standard material that has been accepted. Solar power sales have grown rapidly with an annual growth rate of about 40% over the past decade and are estimated to be 3.8 gigawatts (GW) production in 2007. Sales are hindered by the lack of grade silicon and high prices. Top grade silicon can also be used, but it is not considered an option because the manufacturing costs will increase several times more.

For typical conventional solar cells, more than half of the manufacturing costs are raw semiconductor polysilicon used to make solar cell wafers. As a result, a typical 14% efficiency solar cell is rated at 0.014 W / cm ² and costs $ 3 / watt (ie, $ 0.042 / cm ² ) at the cost of a silicon wafer prior to any additional manufacturing. Is over. Therefore, the existing photovoltaic industry needs to address and solve the fact that the starting cost of silicon material alone exceeds the reference price utility required for large-scale applications. In contrast, semiconductor manufacturers that produce microprocessor chips that sell for more than $ 100 / cm ² per unit area can afford the costs associated with the use of top grade silicon wafers.

  The shortage of solar grade silicon and the inability of the photovoltaic industry to meet critical criteria costs, coupled with the advent of new more efficient triple junction solar cells developed for space applications, It has generated considerable new interest in photovoltaic concentrators. The obvious advantage of photovoltaic concentrators is the use of large area, inexpensive materials (glass reflectors or plastic lenses) to concentrate sunlight on a much smaller area of expensive solar cells, and thus cheap materials. This is a cost-effective possibility resulting from using and replacing expensive materials. By designing a solar concentrator with a solar intensity of 1000, the need for expensive semiconductor silicon will be significantly reduced to approximately 99.9%, which is currently required for 1 MW conventional solar cells. This means that a 1000 MW VMJ battery is possible using the same amount of expensive semiconductor silicon. In practice, this is considered a practical approach to alleviate any silicon deficiency problem.

  Substantial research on solar concentrators has focused primarily on the development of high-strength solar cell silicon concentrator designs, with considerable work being developed during the energy crisis of the 1970s, Indicates that it is only cost effective from moderate to insufficient. Initially, research and development was conducted on silicon cells for concentrator systems operating at a solar intensity of 500, but when trying to overcome the series resistance problem in the solar cell design under investigation, When encountering developmental difficulties, this target was lowered to a solar intensity of 250. For example, high series resistance loss in concentrator solar cells is well understood as a major problem, and conventional VMJ solar cell technology has addressed and solved it. A significant portion of solar cells developed for concentrator technology involves six or seven high temperature steps (> 1000 ° C.) and six or seven photolithography masking steps, which are fairly complex and costly to manufacture. Note that this is the case. This complexity was attributed to design efforts to minimize series resistance losses, even with the best of these designs, with maximum intensity operation essentially limited to a solar intensity of at most 250. Such complexity and associated costs hindered the substantial development of concentrator technology and related solar cell technology, and encouraged the development of alternative technologies such as thin film solar cell technology.

Vertical multi-junction (VMJ) solar cell technology is substantially different from conventional concentrator solar cells. VMJ solar cell technology offers at least the following two advantages over other technologies. (1) No photolithography is required. (2) A single high temperature diffusion step at temperatures above 1000 ° C. can be used to form both junctions. Therefore, a cheaper manufacturing cost can be obtained. Further, the VMJ solar cell can operate at a high intensity such as a solar intensity 2500, for example. It can be readily seen from this behavior that series resistance is not a problem in VMJ battery design, even at high solar intensities, which are not economically feasible according to common wisdom. . Also, the current density in the VMJ unit cell at a solar intensity of 2500 is generally near 70 A / cm ^2, a radiation level that can be substantially harmful to most solar cells based on other technologies.

As noted above, new interest in solar power concentrators is the Group III-V materials that primarily include gallium (Ga), phosphorus (P), arsenide (As), indium (In), and germanium (Ge). This is due to the development of a triple-junction solar cell fabricated in Triple junction cells can use 20-30 separate layers of semiconductor in succession on a germanium wafer, which are grown in a metal organic chemical vapor deposition (MOCVD) reactor. GaInP ₂ and GaAs doped layers, each type of semiconductor having a unique band gap energy that absorbs sunlight of a particular color most efficiently. These semiconductor layers are carefully selected to generate electricity from as much sunlight as possible by absorbing almost all of the solar spectrum. These multi-junction devices are the most effective solar cells to date, reaching a record high efficiency of 40.7% under moderate sunlight concentration and laboratory conditions. However, these manufactures are expensive and require use in solar power concentrators.

  However, the demand and cost of group III-V solar cell materials are rising rapidly. As an example, in 12 months (December 2006-December 2007), the cost of pure gallium rose from about $ 350 per kg to $ 680 per kg, and the price of germanium ranges from $ 1000 per kg It rose substantially to $ 1200. The price of indium, which was $ 94 per kg in 2002, rose to nearly $ 1000 per kg in 2007. Also, with the large-scale manufacturing of thin film CIGS (CuInGaSe) solar cells started by several new companies in 2007, the demand for indium continues to rise. In addition, indium is a rare element widely used to form transparent electrical coatings in the form of indium tin oxide for liquid crystal displays and large flat panel monitors. Realistically, these materials are a viable long-term solution for photovoltaic (PV) that is needed to provide terawatts of low-cost power in solving major global energy problems. I don't think so.

Semiconductor solar cell of the group III ~V Group area 0.26685Cm ² is able to generate power 2.6 watts or about 10 W / cm ^2, such techniques, eventually 8-10 cents / kWh Although it has been estimated that electricity can be generated and is substantially similar to the price of electricity from conventional power sources, further analysis may be needed to establish such an assessment. However, the VMJ solar cell showed output power in excess of 40 W / cm ² at a solar intensity of 2500 using the cheapest semiconductor material with low cost manufacturing. (This output power exceeds 400,000 W / m ² ). In addition to complex PV technology based on high performance materials, Si-based solar cell technology continues to be a substantially major technology in photovoltaic elements and applications. In addition, if a global need arises, silicon will be able to supply terawatt solar power for a wide range of global applications within a predictable future range. It is the only semiconductor material that has

  The following presents a simplified summary to provide a basic understanding of some aspects described herein. This summary is not an extensive overview and is not intended to identify key / critical elements or to delineate the scope of the various aspects described herein. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

  The present invention provides semiconductor-based photovoltaic cells and processes that mitigate recombination losses of photogenerated carriers. In one aspect, to reduce recombination loss, the diffusion doping layer of the active photovoltaic element is coated with a pattern of dielectric material that reduces the contact between the metal contact and the active PV element. A variety of patterns can be utilized, and one or more surfaces of the PV element can be coated with one or more dielectrics. Vertical multi-junction (VMJ) solar cells can be fabricated with patterned PV elements or unit cells. Patterned PV elements can increase the series resistance of the VMJ solar cell, and patterning one or more surfaces of the PV element makes the process used to make the VMJ solar cell more complex However, reducing the carrier loss of the diffusion doping layer can increase the efficiency of the solar cell and thus provide the advantage of PV operation over manufacturing complexity. A system is also provided that enables the manufacture of semiconductor-based PV cells.

  Aspects or features described herein, and related advantages such as reducing recombination loss of photogenerated carriers, include all classes of photovoltaic cells, such as solar cells, thermophotovoltaic cells, or cells that are excited with laser source photons. Can be used in. Furthermore, the present invention can be practiced with other classes of energy conversion batteries such as beta voltaic batteries.

  The present invention mitigates most recombination losses in vertical multiple junction (VMJ) cells by texturing on the light receiving surface. The texture may be in the form of a groove in the form of a cavity, such as a “V” -shaped cross-sectional configuration, “U” -shaped cross-sectional configuration, and the surface containing such a cross-sectional configuration forms a VMJ. It is substantially perpendicular to the direction in which the unit cells are stacked. In one aspect, a plane that includes a substantially repeating cross-section (eg, a plane that cuts in the direction in which the grooves extend) is substantially perpendicular to the direction in which the unit cells are stacked. Such a mechanism makes it easy to guide the refracted light away from the diffusion doped regions of the p + and n + VMJs, and at the same time generate the desired carriers with a reduced volume. Therefore, incident light can be refracted on a plane that includes this cross-sectional configuration and is substantially perpendicular to the direction in which the unit cells are stacked.

  It should be understood that the VMJ texturing of the present invention differs from the prior art for conventional silicon photovoltaic cell texture (both relate to the direction of the PN junction and / or interaction with incident light). For example, conventional silicon photovoltaic cells generally absorb light at longer wavelengths closer to the PN junction (located horizontally) in order to better collect carrier currents. Textured to tilt the penetration of the light, thus mitigating the lack of spectral response to longer wavelength light in the solar spectrum. In contrast, in a VMJ of the present invention that includes a vertical junction and thus already provides an improved spectral response to longer wavelength light in the solar spectrum, this is not necessary.

  In a specific aspect, the result of implementing the groove (eg, V-shaped groove) of the present invention is a conventional solar cell with texturing (which reduces reflection or brings reflected or refracted light closer to the junction). Reducing bulk recombination losses by reducing bulk volume (as opposed to surface). Specifically, VMJ cells show better carrier current collection for both short and long wavelength light, and the response to short wavelength light is a highly doped horizontal junction on the top surface. The response to long wavelength light is due to the improved collection efficiency of the vertical junction. As another example, instead of a grooved texture in the form of a cavity according to the present invention, for example, random, pyramid, dome and other textures with similar protruding configurations are implemented as part of the VMJ. , Incident light is refracted in all directions and light is absorbed in the p + and n + diffusion regions, thus reducing efficiency.

  According to a related method, a VMJ can be formed by first stacking a plurality of cell units, each cell itself comprising a plurality of parallel semiconductor substrates or layers stacked on top of each other. it can. Each layer can be made of a semiconductor material that is doped with impurities to form a PN junction, and further includes a “built-in” electrostatic drift electric field that enhances the movement of minority carriers toward such a PN junction. Including. Later, a plurality of such cell units are integrated to form a VMJ. Next, a groove in the form of a resonator can be formed on the surface of the VMJ battery that receives the light (eg, by a dicing saw), and the plane including the cross-sectional configuration is in the direction in which the unit cells forming the VMJ are stacked. It is substantially perpendicular to it. Thus, incident light can be refracted in a plane that is substantially perpendicular to the direction of unit cell stacking, including repeated cross-sectional configurations (eg, higher in relation to a given depth in that regard). Bring about absorption). In addition, various backsides and sides with reflective coatings can be implemented with various embodiments of the present invention.

  In a related aspect, the grooved surface of the present invention further improves carrier collection while reducing most recombination losses. For example, a V-shaped groove increases the absorption path of longer wavelength light in the solar spectrum, and light absorption can be substantially confined within the n-type majority region of the p + nn + unit cell. Thus, it can be arranged perpendicular to the p + nn + (or n + pp +) unit cell. Furthermore, such a V-shaped groove can have an anti-reflective coating provided to improve the absorption of light incident on the cell.

  In a related aspect, the present invention mitigates most recombination losses in vertical multiple junction (VMJ) cells by texturing on the light receiving surface. The texture may be in the form of a groove in the form of a resonator, such as a “V” -shaped cross-sectional configuration, a “U” -shaped cross-sectional configuration, etc. It is substantially perpendicular to the stacking direction. In one aspect, a plane that includes a substantially repeating cross-section (eg, a plane that cuts in the direction in which the grooves extend) is substantially perpendicular to the direction in which the unit cells are stacked. Such a mechanism makes it easier to guide the refracted light away from the diffusion doped regions of the p + and n + VMJs, while at the same time producing the desired carriers with a reduced volume. Therefore, incident light can be refracted in a plane that is substantially perpendicular to the direction in which the unit cells are stacked, including this cross-sectional configuration.

  It should be understood that the VMJ texturing of the present invention differs from the prior art for conventional silicon photovoltaic cell texture (both relate to the direction of the PN junction and / or interaction with incident light). For example, conventional silicon photovoltaic cells generally absorb light at longer wavelengths closer to the PN junction (located horizontally) in order to better collect carrier currents. Textured to tilt the penetration of the light, thus mitigating the lack of spectral response to longer wavelength light in the solar spectrum. In contrast, in a VMJ of the present invention that includes a vertical junction and thus already provides an improved spectral response to longer wavelength light in the solar spectrum, this is not necessary.

  In a specific aspect, the result of implementing the groove (eg, V-shaped groove) of the present invention is a conventional solar cell with texturing (which reduces reflection or brings reflected or refracted light closer to the junction). Reducing bulk recombination losses by reducing the bulk volume (as opposed to the surface). Specifically, the VMJ cell exhibits better carrier current collection for both short and long wavelength light, and the response to short wavelength light is a highly doped horizontal junction at the top surface. The response to long wavelength light is due to the improved collection efficiency of the vertical junction. As another example, instead of a grooved texture in the form of a resonator of the present invention, incidents may be implemented when other textures, such as random, pyramid, dome and similar protruding configurations are implemented as part of the VMJ. Light is refracted in all directions and is absorbed in the p + and n + diffusion regions, thus reducing efficiency.

  According to a related method, a VMJ can be formed by first stacking a plurality of cell units, each cell itself including a plurality of parallel semiconductor substrates or layers stacked together. Can do. Each layer can be made of a semiconductor material that is doped with impurities to form a PN junction, and further includes a “built-in” electrostatic drift electric field that enhances the movement of minority carriers toward such a PN junction. Later, a plurality of such cell units are integrated to form a VMJ. Next, a groove in the form of a resonator can be formed on the surface of the VMJ battery that receives the light (eg, by a dicing saw), and the plane including the cross-sectional configuration is in the direction in which the unit cells forming the VMJ are stacked. It is substantially perpendicular to it. Thus, incident light can be refracted in a plane that is substantially perpendicular to the direction in which the unit cells are stacked, including repeated cross-sectional configurations (eg, more in relation to a given depth in that regard). High absorption). In addition, various backsides and sides with reflective coatings can be implemented with various embodiments of the present invention.

  In a related aspect, the grooved surface of the present invention further improves carrier collection while reducing bulk recombination losses. For example, a V-shaped groove increases the absorption path of longer wavelength light in the solar spectrum, and light absorption can be substantially confined within the n-type majority region of the p + nn + unit cell. Thus, it can be arranged perpendicular to the p + nn + (or n + pp +) unit cell. Furthermore, such a V-shaped groove can have an anti-reflective coating provided to improve the absorption of light incident on the cell.

  In another aspect, the present invention provides a buffer zone in the final layer of a high voltage silicon vertical multiple junction (VMJ) photovoltaic cell to provide a barrier that protects the active layer while providing ohmic contact. Such a buffer zone may be in the form of an inert layer feature additionally layered on and / or below the final layer of the VMJ cell. A VMJ battery may itself include multiple cell units, each cell unit using several (eg, three) active layers, using a PN junction and a “built-in” electrostatic drift electric field (which is a PN Strengthen the movement of minority carriers towards bonding).

  As such, various active layers, such as nn + and / or p + n junctions placed on both ends of the VMJ battery (as part of the battery unit) can be subjected to harmful forms of stress and / or strain (eg, thermal / mechanical compression, From torsion, moments, shears, etc. that can be induced during the manufacture and / or operation of the VMJ. Furthermore, the buffer zone can be formed of a material having a substantially low resistivity ohmic contact, either metal or semiconductor, so that it does not contribute to substantial series resistance loss in the photovoltaic cell in the operating state. . For example, the buffer zone can be formed by using a p-type doped low resistivity silicon wafer, so that when using other p-type dopants such as aluminum alloys in the manufacture of VMJ photovoltaic cells, This buffer zone is self-doping (in contrast to the use of n-type wafers, which can create undesirable pn junctions) when the goal is to produce a substantially low resistivity ohmic contact. -doping) risk will be mitigated. It should be understood that the present invention can be implemented as part of any class of photovoltaic cells, such as solar cells or thermal photovoltaic cells. Furthermore, aspects of the invention can be practiced with other classes of energy conversion batteries, such as beta voltaic batteries.

  In a related aspect, the buffer zone may be in the form of a perimeter on the surface of the final layer of the cell unit, which can serve as a protective boundary for such an active layer and even handle the VMJ battery A frame is attached to facilitate transportation. Similarly, by providing a safe handle for the VMJ battery, the formation of such a rim facilitates operations associated with the anti-reflective coating (eg, mechanically clamping the battery over the coating). The coating can be applied evenly when reliably held during operation, for example). In addition, the buffer zone (eg, an inert layer disposed at the end of the VMJ) can be physically positioned adjacent to other buffer zones during deposition, and thus any accidental intrusion underneath the contact surface. Undesirable dielectric coating materials can also be easily removed without damaging the active unit cell. The buffer zone can be formed from substantially low resistivity, highly doped silicon (eg, about 0.008 inches thick). Such a buffer zone can later be contacted with a conductive lead that divides or separates the VMJ cell from another VMJ cell in the array of photovoltaic cells.

According to a further aspect, the buffer zone can be sandwiched between the electrical contact and the active layer of the VMJ battery. Further, such buffer zones can have thermal expansion properties that substantially match the thermal expansion properties of the active layer, thus mitigating performance degradation (eg, during lead welding or soldering in manufacturing). Mitigates the stress / strain that occurs). For example, a heavily doped low resistivity silicon layer can be used that matches the thermal expansion coefficient (3 × 10 ⁻⁶ / ° C.) of all active unit cells. Thus, a substantially strong ohmic contact can be provided to the active unit cell, which further mitigates stress problems caused by improper combinations of thermal expansion coefficients in welding / soldering and / or contact materials. To do. Other embodiments include tungsten (4.5 × 10 ⁻⁶ / ° C.) selected for a thermal expansion coefficient substantially similar to p + nn + unit cells of active silicon (3 × 10 ⁻⁶ / ° C.). Or introducing a metal layer such as molybdenum (5.3 × 10 ⁻⁶ / ° C.). Metallization applied to the outer layer of the low resistivity silicon layer in the buffer zone or to the metal layer of the electrode that becomes the alloy of the active unit cell welds without introducing harmful stress to high-strength solar cells or photovoltaic cells Such an outer layer acts as an ohmic contact rather than a segment of unit cells in series with other unit cells.

  Various aspects of the present invention can be implemented as part of a wafer having a Miller Index (111) of the relevant crystal plane orientation of the buffer zone, which is commonly used to make active VMJ unit cells. It is considered to be mechanically stronger and slower to etch than the crystalline silicon (100) obtained. Thus, the low resistivity silicon layer can have a different crystal orientation than the active unit cell, and using such an alternative orientation results in a device with improved mechanical strength / final contact. It is. In other words, the edge of the oriented unit cell (100) is generally etched faster compared to the oriented inert final layer (111), and the active unit cell having such a crystal orientation The corners are essentially rounded, thus providing a more stable device structure with higher mechanical strength for welding or otherwise connecting the final contacts.

  In a related aspect, the present invention uses vertical multiple junction (VMJ) photovoltaic cells to effect electrolysis (eg, production of hydrogen and oxygen) of a compound (eg, water) by incident light and current generated for electrolysis. Such a VMJ includes a plurality of cell units that are in contact with the electrolyte, and each cell unit uses several (eg, three) active layers to form a PN junction and a “built-in” electrostatic drift electric field (which Strengthen the movement of minority carriers toward the PN junction). The VMJ can be partially or fully immersed in water / electrolyte as part of a transparent housing such as glass or plastic, and when such VMJ is exposed to light, a plurality of electrolytic electrodes ( Anode / cathode) can be formed through the VMJ. Such current flowing between the electrolytic electrodes flows through the water and breaks the water into hydrogen and oxygen whenever the threshold voltage for electrolysis is reached. In general, the threshold voltage for such decomposition is in the range of 1.18 volts to 1.6 volts to split the water to produce hydrogen and oxygen. It should be understood that a high voltage can be reached by stacking multiple cell units (eg, connecting multiple cells in series). In addition, catalyst additives can be further used to improve hydrogen and oxygen generation efficiency and reduce semiconductor corrosion caused by high electrode potential and electrolyte solution. Furthermore, the electrolyte can be formed of any solution that does not adversely affect the stack forming the VMJ battery (eg, an iridium-based material made of iridium, its binary alloy, or its oxide).

In a related aspect, the VMJ can be partly or fully immersed in water / electrolyte and can include protruding metal regions (eg, VMJ electrodes) that protrude above the silicon of the VMJ battery, The contact area with the liquid is increased and hydrogen production is enhanced. Such protrusions can be, for example, a few millimeters. According to a further aspect, a substantially thin layer of an electrocatalytic material such as platinum, RuO ₂ , or titanium can be incorporated into the metallization during the manufacture of the VMJ cell to enhance hydrogen formation. In addition, since the negative (−) side of metallization can be different from the positive (+) side of p +, there is considerable flexibility in selecting electrical contact materials. One skilled in the art will appreciate that catalyst materials can be easily selected to enhance hydrogen production, be stable, and be compatible with VMJ battery production. Furthermore, an ultrasonic unit can be used to release the generated oxygen or hydrogen bubbles that remain attached to the electrolytic electrode. It should be understood that the electrolyte flow can also remove such formed bubbles.

  According to a related method, an electrolyte solution is introduced into a container containing the VMJ, and the VMJ is completely or substantially immersed. Such a system is then exposed to incident light and the current generated from the VMJ flows. Incident light on the VMJ can generate a current through the electrolyte solution, and water electrolysis occurs at any location that reaches or exceeds the threshold for water decomposition (eg, about 1.6 volts). It is. For example, a voltage of 0.6 volts can be generated across each unit cell (eg for solar intensity 1000), and electrolysis can occur between the first unit cell region and the third unit cell region. Can be done. Thus, various collection mechanisms (eg, membranes, mesh plates, etc.) for collecting the generated oxygen and hydrogen gases can be used to break down water when the voltage exceeds the threshold for water electrolysis (eg, about 1.6 volts). It can be placed between the expected areas. It should be understood that such a collection mechanism can also be positioned downstream of the electrolyte flow so as to collect the produced oxygen and hydrogen gases.

  To the accomplishment of the foregoing and related ends, specific illustrative aspects are described herein in connection with the following description and the annexed drawings. These aspects illustrate the various ways in which they can be implemented, all of which are intended to be included herein. Other advantages and novel features may become apparent from the following detailed description when considered in conjunction with the drawings.

1 is a schematic perspective view illustrating a surface that is textured or grooved as part of a vertical multiple junction (VMJ) cell according to one aspect of the present invention. FIG. The figure which shows the example cross section for implementing the groove | channel of this invention. FIG. 4 illustrates an exemplary stack of cell units for forming a VMJ having a grooved surface according to one aspect of the present invention. FIG. 6 illustrates a specific unit cell that partially forms a VMJ according to one aspect of the present invention. FIG. 4 illustrates a related method of making a VMJ having a grooved surface to mitigate bulk recombination losses according to one aspect of the present invention. 1 is a schematic block diagram illustrating the arrangement of buffer zones as part of a vertical multiple junction (VMJ) battery according to one aspect of the present invention. FIG. 4 shows a particular embodiment of unit cells whose array can form a VMJ battery according to a particular embodiment of the present invention. The figure which shows the example cross section of the buffer zone of the form of the periphery formation on the surface of the unit cell arrange | positioned at both ends of VMJ. FIG. 4 illustrates a related method of using a buffer zone in the final layer of a high voltage silicon vertical multiple junction (VMJ) photovoltaic cell to provide a barrier that protects its active layer. 1 is a schematic cross-sectional view illustrating a solar cell assembly that includes a modular mechanism of a photovoltaic (PV) cell that can implement a VMJ having a buffer zone. FIG. 1 is a schematic block diagram illustrating an electrolysis system using a vertical multiple junction (VMJ) battery for water electrolysis according to an aspect of the present invention. The figure which shows the protrusion part of the metal layer from the surface of VMJ which can accelerate | stimulate an electrolysis process. The figure which shows the voltage gradient over the whole of a laminated type battery as VMJ and its part. The figure which shows the method of the water electrolysis by VMJ by 1 aspect of this invention. The figure which shows the VMJ battery which can be used for the electrolysis of this invention. The figure which shows one of the cell units which forms multiple VMJ for electrolysis of this invention. FIG. 3 shows a VMJ battery having a grooved surface to improve the efficiency of the electrolysis process. FIG. 3 illustrates exemplary grooves for the surface of a VMJ used for electrolysis according to one aspect of the present invention. FIG. 6 is a diagram of an example configuration of a patterned surface of a PV element according to aspects disclosed in the present application. FIG. 6 is a diagram of an example configuration of a patterned surface of a PV element according to aspects disclosed in the present application. FIG. 4 shows an example of a set of precursors and derived PV elements that can be made by doping according to aspects described herein. FIG. 4 illustrates an example VMJ stack and a patterned dielectric coating configuration of a PV device according to aspects described herein. FIG. 4 illustrates an example VMJ stack and a patterned dielectric coating configuration of a PV device according to aspects described herein. FIG. 4 illustrates an example VMJ stack and a patterned dielectric coating configuration of a PV device according to aspects described herein. The figure which shows the PV battery of VMJ processed so that the specific crystal surface might be exposed. FIG. 4 illustrates an example VMJ stack and a patterned dielectric coating configuration of a PV device according to aspects described herein. FIG. 4 illustrates an example VMJ stack and a patterned dielectric coating configuration of a PV device according to aspects described herein. FIG. 4 illustrates an example VMJ stack and a patterned dielectric coating configuration of a PV device according to aspects described herein. FIG. 5 illustrates an example configuration of a patterned dielectric coating for an active PV device having a reduced diffusion doping layer in accordance with aspects described herein. FIG. 4 illustrates an example configuration of a patterned dielectric coating of a PV device according to aspects described herein. FIG. 4 illustrates an example configuration of a patterned dielectric coating of a PV device according to aspects described herein. 1 is a perspective view illustrating one embodiment of a photovoltaic cell having a textured surface according to aspects described herein. FIG. 6 is a flow diagram of one embodiment of a method of making a photovoltaic cell with reduced carrier recombination loss in accordance with aspects disclosed herein. 5 is a flow diagram illustrating one embodiment of a method of making a VMJ solar cell with reduced carrier recombination loss in accordance with aspects described herein. 1 is a block diagram of one embodiment of a system that enables manufacturing of solar cells according to aspects described herein. FIG.

  The present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It may be evident, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the present invention.

  In the description of the invention, the appended claims, or the drawings, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless otherwise specified or apparent from the context, “X uses A or B” is intended to mean an inclusive generic substitution. That is, if X uses A, X uses B, or X uses both A and B, then "X uses A or B" We are satisfied with. Further, the articles “a” and “an” as used herein and in the accompanying drawings generally refer to “one or more” unless the context clearly dictates otherwise. It should be interpreted as meaning.

  Further, with respect to the terminology of doped materials that are part of the photovoltaic cell described herein, the terms “n-type” and “N-type” are interchangeable for doping with donor impurities. The same applies to the terms “n + type” and “N + type”. With respect to doping with acceptor impurities, the terms “p-type” and “P-type” are still used interchangeably, as are the terms “p + -type” and “P + -type”. For ease of understanding, doping types may appear abbreviated, for example, n-type is labeled N and p + -type is shown as P +. Multi-layer photovoltaic elements or unit cells are labeled as a set of letters, each indicating the layer doping type, for example, a p-type / n-type junction is labeled PN, On the other hand, p + type / n type / n + type junctions are denoted by P + NN +, and the labeling of other junction combinations also adheres to this notation.

  FIG. 1 is a schematic perspective view showing a grooved surface 100 as part of a vertical multi junction (VMJ) cell 120 according to one aspect of the present invention. With this mechanism of texturing 100, the refracted light can be directed away from the p + and n + diffused doped regions while simultaneously producing the desired carriers. Thus, incident light can be refracted at the surface 110 having the normal vector n. Such a surface 110 may be parallel to the PN junction surface of the VMJ 120 and include the cross-sectional configuration of the groove 100. In addition, an anti-reflective coating can be applied to the textured surface 100 so that the absorption of incident light in the battery is increased. In other words, the orientation of the surface 110 is substantially perpendicular to the direction in which the unit cells 111, 113, and 115 are stacked. It is understood that other non-vertical orientations (eg, where the crystal plane is exposed at various angles) can be contemplated and all such aspects are to be considered within the scope of the present invention. I want.

  FIG. 2 shows an exemplary texture for carving a groove in the surface of a VMJ that receives light. Such a groove forms a cavity-shaped groove such as a “V” -shaped cross-sectional configuration having various angles (for example, 0 ° <<< 180 °), a “U” -shaped cross-sectional configuration, and the cross-sectional configuration. Is substantially perpendicular to the direction in which the unit cells forming the VMJ are stacked and / or substantially parallel to the PN junction of the VMJ. It should be understood that the texturing 210, 220, 230 for the VMJ of the present invention differs from the prior art for texture of conventional silicon photovoltaic cells in PN junction orientation and / or interaction with incident light. For example, conventional silicon photovoltaic cells are typically textured to incline light penetration, so that longer wavelength light is placed in a PN junction (horizontally arranged) to better collect the carrier current. Are absorbed more near, thus mitigating the lack of spectral response for longer wavelengths of light in the solar spectrum. In contrast, in a VMJ of the present invention that includes a vertical junction and already provides an improved spectral response to longer wavelength light in the solar spectrum, this is not necessary.

  Rather, one aspect for implementing the groove (eg, V-shaped groove) of the present invention is the surface of a conventional solar cell (with reduced texturing or texturing where reflected or refracted light approaches the junction) In contrast, the bulk recombination loss is mitigated by reducing the bulk volume. Specifically, the VMJ cell shows better carrier current collection for both short and long wavelength light, and the response to short wavelength light is high on the top surface. This is due to the removal of the lightly doped horizontal junction, and the response to long wavelength light is due to the enhanced collection efficiency of the vertical junction. As another example, instead of a grooved texture in the form of a resonator of the present invention, incidents may be implemented when other textures, such as random, pyramid, dome and similar protruding configurations are implemented as part of the VMJ. Light is refracted in all directions and is absorbed in the p + and n + diffusion regions, thus reducing efficiency. It should be understood that such “U” shaped grooves and “V” shaped grooves are exemplary in nature and that other configurations are well within the scope of the present invention.

  FIG. 3 illustrates the mechanism of unit cells 311, 313, and 317 that can implement the grooved texture of surface 345 according to one aspect of the present invention. As described previously, the VMJ 315 is formed of a plurality of (1 to k, k is an integer) integrally joined cell units 311, 313, and 317, each cell unit itself being a stacked substrate or Formed from layers (not shown). For example, each cell unit 311 may include a plurality of parallel semiconductor substrates stacked on one another made of an impurity-doped semiconductor material, the material comprising a PN junction and a minority carrier toward the PN junction. Creates a “built-in” electrostatic drift field that enhances motion. It should be understood that the formation of various N + and P-type doping layers can be implemented as part of the cell unit, and such mechanisms are well within the scope of the present invention.

  Thus, the texture on the light-receiving surface 345 facilitates generating desired carriers at the same time that the refracted light is directed away from the p + and n + diffused doped regions. Accordingly, the incident light can be refracted in a plane that is substantially perpendicular to the direction in which the unit cells are stacked (eg, perpendicular to the vector n), including the cross-sectional configuration.

  FIG. 4 shows a specific embodiment of a unit cell whose array can form a VMJ battery with textured grooves of the present invention. The unit cell 400 includes layers 411, 413, 415 that are stacked on each other in a substantially parallel arrangement. Such layers 411, 413, 415 can further include a semiconductor material doped with impurities, where layer 413 is of one conductivity type and layer 411 is of the opposite conductivity type at intersection 412. A PN junction is defined. Similarly, layer 415 can have the same conductivity type as layer 413 but have a substantially higher impurity concentration, thus creating a built-in electrostatic drift electric field that enhances minority carrier motion toward PN junction 412. . Such unit cells can be joined together to form a VMJ, and the surface is grooved according to various aspects of the invention.

  According to a further aspect, in order to fabricate a VMJ from a plurality of cells 400, first a high resistivity (eg, greater than 100 Ωcm) N-type (or P-type) silicon having a thickness of about 0.008 inches. The same PNN + (or NPP +) junction can be formed in a flat wafer at a depth of about 3 μm to 10 μm. Subsequently, such PNN + wafers are stacked together with a thin layer of aluminum sandwiched therebetween, and the PNN + junction and crystal orientation of each wafer can be oriented in the same direction. In addition, an aluminum-silicon eutectic alloy or a metal having a thermal coefficient substantially matching that of silicon, such as molybdenum or tungsten, can be used. The silicon wafer and aluminum interface can then be alloyed together so that the stacked assemblies can be bonded together. A buffer zone having a substantially low resistivity can also be provided in the form of a passive layer mechanism additionally stacked above and / or below the final layer of the VMJ cell, thus detrimental Protects the active layer from various forms of stress and / or strain (eg thermal / mechanical compression, torsion, moment, shear, etc. that may be induced during the manufacture and / or operation of the VMJ) Barriers are implemented. The surface of such a cell can then be grooved to mitigate bulk recombination losses, as previously described in detail. It should be understood that other materials such as germanium and titanium can also be used. Similarly, an aluminum-silicon eutectic alloy can also be used.

  FIG. 5 shows a related method 500 for carving a groove in the surface of a VMJ that receives light. Although an exemplary method is illustrated and described herein as a series of blocks representing various events and / or actions, the invention is not limited by the illustrated ordering of such blocks . For example, some acts or events may occur in a different order and / or simultaneously with respect to other acts or events, away from the ordering presented herein by the present invention. Also, not all illustrated blocks, events or actions may be required to implement a method in accordance with the present invention. Further, it will be appreciated that the exemplary methods and other methods according to the present invention may be implemented in connection with the methods illustrated and described herein, as well as other systems and devices not shown or described. .

  Initially, at 510, a plurality of cell units having PN junctions are formed as previously described in detail. As previously described, each cell unit may itself comprise a plurality of parallel semiconductor substrates or layers stacked together. Each layer can be made of a semiconductor material that is doped with impurities to form a PN junction, and further includes a “built-in” electrostatic drift electric field that enhances the movement of minority carriers toward such a PN junction. Subsequently, at 520, a plurality of such cell units are integrated to form a VMJ and buffered as protection (eg against stress / strain induced on the battery during manufacture) of such a battery. Zones can be implemented. Next, at 530, a groove in the shape of a cavity can be formed (eg, by a dicing saw) on the surface of the VMJ cell that receives the light, and the surface including this cross-sectional configuration forms the VMJ. Is substantially perpendicular to the direction in which the unit cells are stacked. Subsequently, at 540, incident light can be refracted at a plane substantially perpendicular to the direction in which the unit cells comprising this cross-sectional configuration (and / or parallel to the PN junction) are stacked.

  FIG. 6 is a schematic block diagram of a mechanism for a buffer zone as part of a vertical multiple junction (VMJ) battery according to an aspect of the present invention. The VMJ 615 itself is formed from a plurality of (1 to n, n is an integer) integrally joined cell units 611 and 617, and each cell unit itself is formed from a stacked substrate or layer (not shown). ). For example, each cell unit 611, 617 can include a plurality of parallel semiconductor substrates stacked on one another made of an impurity-doped semiconductor material, the material being a PN junction and a small number towards such a PN junction. Creates a “built-in” electrostatic drift field that enhances carrier motion. Accordingly, various active layers, such as nn + and / or p + n junctions, or pp + and / or pn + junctions placed at both ends of the VMJ battery 615 (as part of its cell unit), can cause harmful forms of stress and / or strain. (E.g., thermal / mechanical compression, torsion, moment, shear, etc. that can be induced during the manufacture and / or operation of the VMJ).

  Further, each of the buffer zones 610, 612 can be formed of a material having a substantially low resistivity ohmic contact (eg, any range with an upper limit of less than about 0.5 Ωcm), while undesirable. Mitigating and / or eliminating auto-doping. For example, to mitigate the risk of self-doping, by using a low resistivity wafer doped p-type with other p-type dopants such as aluminum alloys (substantially low resistivity ohmic contacts Buffer zones 610, 612 can be formed (as opposed to using n-type wafers that can create undesirable pn junctions).

  FIG. 7 shows a particular embodiment of a unit cell whose array can form a VMJ battery. The unit cell 700 includes layers 711, 713, 715 stacked on each other in a substantially parallel arrangement. Such layers 711, 713, 715 may further include a semiconductor material doped with impurities, where layer 713 is of one conductivity type and layer 711 is of the opposite conductivity type at intersection 712. A PN junction is defined. Similarly, layer 715 can be of the same conductivity type as layer 713 but can have a substantially higher impurity concentration, thus creating a built-in electrostatic drift field that enhances minority carrier motion toward PN junction 712. . Such unit cells can be joined together to form a VMJ, and the buffer zones of the present invention are arranged to protect the VMJ and associated unit cells and / or the layers that form them. Can do.

  According to a further aspect, in order to fabricate a VMJ from a plurality of cells 700, first a high resistivity (eg, greater than 100 Ωcm) N-type (or P-type) silicon having a thickness of about 0.008 inches. The same PNN + (or NPP +) junction can be formed in a flat wafer at a depth of about 3 μm to 10 μm. Subsequently, such PNN + wafers are stacked together with a thin layer of aluminum sandwiched between each wafer, and the PNN + junction and crystal orientation of each wafer can be oriented in the same direction. In addition, an aluminum-silicon eutectic alloy or a metal having a thermal coefficient substantially consistent with that of silicon, such as molybdenum or tungsten, can be used. The silicon wafer and aluminum interface can then be alloyed together so that the stacked assemblies can be bonded together. Furthermore, an aluminum-silicon eutectic alloy can also be used. It should be understood that various N + and P-type doping layers can be implemented as part of the cell unit, and such mechanisms are well within the scope of the present invention.

  A buffer zone having a substantially low resistivity can also be provided in the form of a passive layer mechanism additionally stacked above and / or below the final layer of the VMJ cell, thus detrimental forms of stress And / or a barrier that protects the active layer from strain (eg thermal / mechanical compression, torsion, moment, shear, etc. that may be induced during the manufacture and / or operation of the VMJ) Is done.

  FIG. 8 shows an exemplary cross section for the buffer zone in the form of a rim formation 810 (812) on the surface of the final layer 831 (841) of the unit cell 830 (840) that partially forms the VMJ battery 800. Show. Such peripheral formations 810, 812 serve as a protective boundary for the active layer of the cell unit, and to facilitate handling and transport of the VMJ battery 800. Partially frame (eg, low resistivity buffer zone and VMJ cell edge or final contact). Similarly, by providing a safe handle for the VMJ battery 800, the formation of the perimeter facilitates operations associated with the anti-reflective coating (eg, by mechanically clamping the battery over the coating, etc.). The coating can be applied evenly when securely held during the operation). Further, such perimeter formation can be physically placed adjacent to other perimeter formations during the deposition process, and any undesirable dielectric coating material that accidentally penetrates below the contact surface can be The cells 830 and 840 can be easily removed without being damaged. The perimeter formation 810 (812) representing the buffer zone can be formed from substantially low resistivity and highly doped silicon (eg, about 0.008 inch thick), Later, the VMJ cell can be contacted with a conductive lead that separates it from another VMJ cell in the array of photovoltaic cells. Furthermore, due to the substantially low resistivity of the buffer zone, conductive leads are not required to obtain full electrical contact to the buffer zone. As such, they may be a partial contact, such as a point contact, or a series of point contacts, and nevertheless provide excellent electrical contact. FIG. 8 is merely exemplary, and other variations (such as a buffer zone 810 formed in manufacturing bonded to the active layer 841 to reach the surface of the VMJ battery 800) are well within the scope of the present invention. Please understand that you enter. For example, the shape of 810 can mean a partial lead contact to a metallized layer on the buffer zone, as previously discussed.

  The conductive lead may be in the form of an electrode layer formed by depositing a first conductive material on a substrate, tungsten, silver, copper, titanium, chromium, cobalt, tantalum, germanium, gold, aluminum Magnesium, manganese, indium, iron, nickel, palladium, platinum, zinc, alloys thereof, indium-tin oxide, other conductive and semiconducting metal oxides, nitrides and silicides, polysilicon, doped Amorphous silicon and various metal composition alloys can be provided. In addition, other doped or undoped conductive or semiconductive polymers, oligomers or monomers, such as PEDOT / PSS, polyaniline, polythiophene, polypyrrole, derivatives thereof, etc. can be used for the electrodes. In addition, non-metallic materials such as amorphous carbon can also be used for electrode formation, as oxide layers that can adversely affect the performance of the VMJ battery may be formed on some metals. . It is understood that the perimeter formation in FIG. 8 is exemplary in nature, and other configurations for the buffer zone are well within the scope of the present invention, such as rectangular, circular, cross-section with various surface contacts with the active layer. I want to be.

  Further, various aspects of the present invention can be implemented as part of a wafer having a mirror index (111) of the associated crystal plane orientation of the buffer zone, which can be used to fabricate an active VMJ unit cell. It is considered to be mechanically stronger and slower to etch than commonly used crystal oriented silicon (100). Thus, the low resistivity silicon layer can have a different crystal orientation than the active unit cell, and using such an alternative orientation results in a device with improved mechanical strength / final contact. It is. In other words, the aligned unit cell (100) is such that the corners of the active unit cell having such a crystal orientation are essentially rounded compared to the aligned inactive final layer (111). ) Are generally etched faster, thus providing a more stable device structure with higher mechanical strength for welding or otherwise connecting the final contacts.

  FIG. 9 shows a related method 900 that uses a buffer zone to provide a barrier that protects the active layer in the final layer of a high voltage silicon vertical multiple junction (VMJ) photovoltaic cell. Although exemplary methods are illustrated and described herein as a series of blocks that represent various events and / or actions, the invention is not limited by the illustrated ordering of such blocks. For example, some acts or events may occur in a different order and / or concurrently with other acts or events, away from the ordering presented herein by the present invention. Also, not all illustrated blocks, events or actions may be required to implement a method in accordance with the present invention. Further, it will be appreciated that the exemplary methods and other methods according to the present invention may be implemented in connection with the methods illustrated and described herein, as well as other systems and devices not shown or described. . Initially, at 910, a plurality of cell units having PN junctions are formed as previously described in detail. As previously described, each cell unit may itself comprise a plurality of parallel semiconductor substrates or layers stacked together. Each layer can be made of a semiconductor material that is doped with impurities to form a PN junction, and further includes a “built-in” electrostatic drift electric field that enhances the movement of minority carriers toward such a PN junction. Subsequently, at 920, a plurality of such cell units are integrated to form a VMJ. Next, at 930, a buffer zone can be implemented that contacts the end layer of the VMJ, providing a barrier that protects the active layer of the VMJ. Such a buffer zone can be in the form of an inert layer feature additionally stacked above and / or below the final layer of the VMJ cell. Then, at 940, a VMJ can be performed as part of the photovoltaic cell.

  FIG. 10 is a schematic cross-sectional view 1000 of a solar cell assembly including a modular mechanism 1020 of photovoltaic (PV) cells 1023, 1025, 1027 (1 to k, k being an integer). Each PV cell can use a plurality of VMJs having a buffer zone according to an aspect of the present invention. In general, each of PV cells (also referred to as photovoltaic cells) 1023, 1025, and 1027 can convert light (eg, sunlight) into electrical energy. The PV cell modular mechanism 1020 can include standardized units or segments that facilitate construction and provide a flexible mechanism.

In an exemplary embodiment, each of the photovoltaic cells 1023, 1025, 1027 may be a dye-sensitized solar cell (DSC) including a plurality of glass substrates (not shown), for example, fluorine. A transparent conductive coating, such as a layer of doped tin oxide, is deposited thereon. Such a DSC includes a semiconductor layer such as TiO ₂ particles that can be sandwiched between glass substrates, a sensitizing dye layer, an electrolyte, and a catalyst layer (not shown) such as Pt. A semiconductor layer can be further deposited on the glass substrate coating, and for example, a dye layer can be adsorbed onto the semiconductor layer as a single layer. Thus, the electrode and counter electrode can be formed with a redox mediator to control the electron flow between them.

  Thus, the batteries 1023, 1025, 1027 undergo an excitation, oxidation, and reduction cycle that produces a flow of electrons, for example electrical energy. For example, incident light 1005 excites dye molecules in the dye layer, and the photoexcited dye molecules subsequently inject electrons into the conduction band of the semiconductor layer. This can cause oxidation of the dye molecules, and injected electrons can flow through the semiconductor layer, creating a current. Thereafter, the electrons reduce the electrolyte in the catalyst layer and convert the oxidized dye molecules to a neutral state. Such excitation, oxidation, and reduction cycles can be continuously repeated to provide electrical energy.

  FIG. 11 is a schematic block diagram illustrating an electrolysis system using a vertical multiple junction (VMJ) battery 1110 for electrolysis according to one aspect of the present invention. The VMJ 1110 can be partially or fully immersed in the water / electrolyte as part of a transparent housing 1130 such as quartz, glass or plastic. When incident light 1135 strikes a surface 1137 of such a VMJ 1110, a plurality of electrolysis electrodes in the form of anodes and / or cathodes can be formed through and / or on the surface 1137 on the VMJ. . The current flowing between such electrolytic electrodes formed on the surface 1137 then flows through the water and breaks the water into hydrogen and oxygen whenever the threshold voltage for electrolysis is reached. The VMJ 1110 includes a plurality (1 to n, n is an integer) of integrally joined cell units 1111 and 1117, and each cell unit itself is formed from a stacked substrate or layer (not shown). For example, each cell unit 1111, 1117 can include a plurality of parallel semiconductor substrates stacked on top of each other made of semiconductor material doped with impurities, the substrate being a PN junction and a small number towards such PN junctions. Creates a “built-in” electrostatic drift field that enhances carrier motion. When incident light 1135 is directed to surface 1137 in various regions of VMJ 1110, multiple cathodes and anodes can then be formed that later function as electrodes for electrolysis operations.

  The current flowing between the electrolytic electrodes flows through the electrolytic solution and decomposes water into hydrogen and oxygen whenever the threshold voltage for electrolysis is reached. In general, the threshold voltage for such decomposition is in the range of 1.18 volts to 1.6 volts in order to decompose water to produce hydrogen and oxygen. It should be understood that a high voltage can be reached by stacking multiple cell units (eg, connecting multiple cells in series). Further, the catalyst material can be further used to improve the generation efficiency of hydrogen and oxygen and reduce the semiconductor corrosion caused by high electrode potential and electrolyte solution. Further, the electrolyte can be formed of any solution that does not adversely affect the stack forming the VMJ battery (eg, an iridium-based catalyst made of iridium, its binary alloy, or its oxide). In a related aspect, an ultrasonic transducer can operably interact with the electrolysis system to release oxygen or hydrogen bubbles that remain attached to the electrolysis electrode.

  The VMJ 1110 may further be disposed on a thermal conditioning assembly 1119 that removes heat generated from the hot spot area to keep the temperature gradient of the VMJ battery within a predetermined level. Such a thermal conditioning assembly 1119 may be in the form of a heat sink mechanism that includes a plurality of heat sinks to be surface mounted on the back of the VMJ, each heat sink extending substantially perpendicular to the back. A plurality of existing fins (not shown) may be further included. The fins can increase the surface area of the heat sink to increase contact with a cooling medium (eg, a cooling fluid such as electrolyte, water, etc.), and the cooling medium can further dissipate heat from the fins and / or photovoltaic cells. Can be used. As such, heat from the VMJ can be conducted through the heat sink into the surrounding electrolyte and / or material that does not affect the electrolysis operation. Furthermore, the heat conduction path (e.g., heat sink to the heat sink (e.g., mitigating direct physical or thermal action of the heat sink to the VMJ battery) and providing a scalable solution for proper operation of the electrolysis (e.g. Metal layer).

  In a related aspect, the heat sink can be placed in a variety of flat or three-dimensional mechanisms for monitoring, adjusting, and comprehensive management of heat flowing away from the VMJ battery. In addition, each heat sink has a spiral, twist, spiral, labyrinth, or other structural shape that has a denser pattern distribution of lines in some parts and a less dense pattern distribution of lines in other parts. Further possible thermal / electrical structures (not shown) can be used. For example, a portion of such a structure can be formed of a material that provides relatively high isotropic conductivity, and another portion can be formed of a material that provides high thermal conductivity in another direction. Can do. Thus, each thermal / electrical structure of the thermal conditioning assembly provides a thermal conduction path that can dissipate heat from the hot spot and direct it into the various thermal conductive layers or heat sinks of the associated thermal conditioning device. And thus promotes electrolysis. It should be understood that the heat sink can be cooled by an independent cooling medium separate from the electrolyte medium.

FIG. 12 shows a further aspect of the present invention that includes metal layer protrusions 1211, 1215 associated with the electrodes of a single unit cell 1201. Such protrusions 1211, 1215 protrude (eg, a few millimeters) from the surface 1241 of the VMJ 1200 to facilitate the electrolysis process by increasing the contact surface area. Also, a substantially thin layer of electrocatalytic material such as platinum, RuO ₂ , or titanium can be incorporated into the metallization during the manufacture of the VMJ cell to enhance hydrogen production. Further, since the negative (−) side 1211 of the metallization can be different from the positive (+) side 1215 of the metallization, there is considerable flexibility in selecting an electrocatalytic material. One skilled in the art will appreciate that catalyst materials can be easily selected to enhance hydrogen production, be stable, and be compatible with VMJ battery production. When incident light 1235 reaches the surface 1241 of the VMJ, a plurality of cathodes / anodes can be formed thereon. For example, a reduction reaction occurs at a negatively charged cathode in the region on the VMJ, and electrons (e ⁻ ) from the cathode are given to a hydrogen caption to form hydrogen gas (a half reaction that balances with the acid ( half reaction)). That is,
Cathode (reduction): 2H ⁺ (aq) + 2e ⁻ → H ₂ (g)
Electrons (e ⁻ ) from the cathode are imparted to the hydrogen caption to form hydrogen gas (a half-reaction in equilibrium with the acid).

The positively charged anode undergoes an oxidation reaction to generate oxygen gas and give electrons to the cathode to complete the circuit. That is,
Anode (oxidation): 2H ₂ O (l) → O ₂ (g) + 4H ⁺ (aq) + 4e ⁻
It is.

As listed below, the same half reaction is balanced with the base. In general, not all half reactions will be balanced with acids or bases. In general, to add a half-reaction, both poles should generally be balanced with either acid or base. That is,
Cathode (reduction): 2H ₂ O (l) + 2e ⁻ → H ₂ (g) + 2OH ⁻ (aq)
Anode (oxidation): 4OH ⁻ (aq) → O ₂ (g) + 2H ₂ O (l) + 4e ⁻
Combining each half-reaction pair results in the same overall decomposition of water to oxygen and hydrogen. That is,
Overall reaction: 2H ₂ O (l) → 2H ₂ (g) + O ₂ (g)
It is.

Thus, as indicated above, the number of hydrogen molecules produced is twice the number of oxygen molecules. Assuming equal temperature and pressure for both gases, the hydrogen gas produced will therefore have twice the volume of the oxygen gas produced. The number of electrons pushed through the water is twice the number of hydrogen molecules produced and four times the number of oxygen molecules produced. As previously described, the conductivity of water increases considerably when a water-soluble electrolyte is added. Thus, the electrolyte separates into captions and anions, which are driven towards the anode where they neutralize the positively charged H ⁺ buildup, and similarly Caption is driven towards the cathode, where it neutralizes the accumulation of negatively charged OH ⁻ . This allows a continuous flow of electricity. It should be understood that the choice of electrolyte should be considered along with the material used for the VMJ battery so as not to adversely affect the material and operation. A further factor in selecting the electrolyte relates to the fact that the anions from the electrolyte compete with the hydroxide ions to let go of the electrons. Electrolyte anions having a lower standard electrode potential than hydroxide are more likely to oxidize than hydroxide and therefore no oxygen gas is produced. Similarly, cations having a higher standard electrode potential than hydrogen ions will be reduced and no hydrogen gas will be produced. To alleviate such an environment, captions such as Li ⁺ , Rb ⁺ , K ⁺ , Cs ⁺ , Ba ²⁺ , Sr ²⁺ , Ca ²⁺ , Na ⁺ , and Mg ²⁺ have lower electrode potentials than H ^+. And is therefore suitable for use as an electrolyte caption. Sodium and lithium can also be used as long as they do not adversely affect the VMJ battery because they form inexpensive and soluble salts.

FIG. 13 shows a graph of voltage-distance at various points on the VMJ 1310, where the unit cells 1311, 1317 intersect or share a common boundary. As shown, the VMJ 1310 includes a plurality of unit cells 1311, 1317 connected in series to increase the voltage as a linear function of the number of cells stacked together (eg, from left to right on the horizontal axis). Can do. As shown in FIG. 13, the voltage difference across cell ₁ is 0.6 volts, and by stacking cell ₂ thereon, such a voltage difference in the combined cell increases to 1.2 volts. To do. Similarly, by stacking cells ₃ thereon, the voltage difference can be increased to 1.8 volts. As such, electrolysis can occur between any two points on the surface of the VMJ that are above the threshold for water degradation. For example, for an open circuit voltage of a 40-junction VMJ battery, 32 volts can be generated at a solar intensity of 1000 (1000 suns) (eg, 0.8 volts per unit cell). Assuming that electrolysis starts at 1.6 volts, only two unit cells are sufficient to supply that voltage. In another aspect, when the load current increases, the voltage determined by the IV characteristics of the VMJ battery at the maximum power of solar intensity 1000 drops to 24 volts, or 0.6 volts per unit cell. Thus, three unit cells may be needed, which contributes 1.8 volts to power the electrolytic reaction. (In general, overvoltage may be required for electrolysis at higher current densities).

  Although electrolysis is described in the context of a single VMJ, the present invention is not so limited and may be part of a plurality of VMJ cells (eg, in parallel and / or in series, or operably separated from each other). It should be further understood that it can be implemented. Adapt VMJ battery design to provide additional contact area to handle larger currents as needed by determining the relationship of currents formed in different regions of the VMJ that exhibit different voltages Can be made. For example, the contact current density can be reduced by increasing the metallization thickness at various points as needed. In addition, various types of pressurization can be used to improve electrolytic efficiency and / or collection of degradation products (eg, hydrogen, oxygen) (eg, sieving mechanisms, filtering mechanisms, etc.). It is to be understood that the present invention is not limited to water electrolysis, and electrolysis of other compounds capable of properly interacting with VMJ is well within the scope of the present invention.

  FIG. 14 illustrates a method 1400 related to water electrolysis with a VMJ according to one aspect of the present invention. Although an exemplary method is illustrated and described herein as a series of blocks representing various events and / or actions, the invention is not limited by the illustrated ordering of such blocks . For example, some acts or events may occur in a different order and / or concurrently with other acts or events, away from the ordering presented herein by the present invention. Also, not all illustrated blocks, events or actions may be required to implement a method in accordance with the present invention. Further, it will be appreciated that the exemplary methods and other methods according to the present invention may be implemented in connection with the methods illustrated and described herein, as well as other systems and devices not shown or described. . Initially at 1410, an electrolyte solution is introduced into a container containing the VMJ, and the VMJ is completely or substantially immersed. Such a system is then exposed to incident light at 1420 and current is generated from the VMJ. Incident light can cause water electrolysis through the electrolyte solution at 1430, where electrolysis occurs at any location that reaches or exceeds the threshold for water decomposition (eg, about 1.2 volts). For example, a voltage of 0.6 volts can be generated across each unit cell (eg for solar intensity 1000), and electrolysis can occur between the first unit cell region and the third unit cell region. Can be done. Accordingly, various collection mechanisms (eg, membranes, sieve plates, etc.) can be placed between regions where the voltage between the regions exceeds a threshold for electrolysis (eg, about 1.6 V), and thus the generated hydrogen Gas is collected at 1440. It should be understood that other collection mechanisms such as downstream of collection can also be used.

  FIG. 15 illustrates a VMJ battery that can be used for electrolysis according to an aspect of the present invention. The VMJ 1515 itself is formed of a plurality of (1 to n, n is an integer) integrally joined cell units 1511 and 1517, and each cell unit itself is formed of a stacked substrate or layer (not shown). ). For example, each cell unit 1511, 1517 can include a plurality of parallel semiconductor substrates stacked on one another made of a semiconductor material doped with impurities, the material being a PN junction and a small number towards such a PN junction. Creates a “built-in” electrostatic drift electric field that enhances carrier motion. Further, by implementing buffer zones 1510, 1512, various active layers such as nn + and / or p + n junctions placed at either end of VMJ battery 1515 (as part of that battery unit) can be detrimental. Against stresses and / or strains (eg, thermal / mechanical compression, torsion, moment, shear, etc., that can be induced in the VMJ during manufacture and / or operation of the VMJ). Each such buffer zone 1510, 1512 has a substantially low resistivity ohmic contact (eg, any range with an upper limit of less than about 0.5 Ωcm) while eliminating and / or mitigating unwanted self-doping. Depending on the material to be formed. For example, to mitigate the risk of self-doping, by using a low resistivity wafer doped p-type with other p-type dopants such as aluminum alloys (substantially low resistivity ohmic contacts Buffer zones 1510, 1512 can be formed (as opposed to using n-type wafers that can create undesirable pn junctions). Catalytic materials (eg, platinum, titanium, etc.) can also be used in the final contact of the VMJ, eg, to facilitate electrolysis.

  FIG. 16 shows a particular embodiment of a unit cell 1600, the array of which can form a VMJ battery for electrolysis of the present invention. Unit cell 1600 includes layers 1611, 1613, 1615 that are stacked on top of each other in a substantially parallel arrangement. Such layers 1611, 1613, 1615 can further include a semiconductor material doped with impurities, where layer 1613 is of one conductivity type and layer 1611 is of the opposite conductivity type at intersection 1612. A PN junction is defined. Similarly, layer 1615 can have the same conductivity type as layer 1613 but substantially higher impurity concentration, thus creating a built-in electrostatic drift electric field that enhances minority carrier motion in PN junction 1612. Such unit cells can be integrated and bonded together to form a VMJ (eg, using catalytic materials for such bonding to enhance electrolysis), Electrolysis is performed as described in detail.

  According to a further aspect, to fabricate a VMJ from a plurality of cells 1600, first a high resistivity (eg, greater than 100 Ωcm) N-type (or P-type) silicon having a thickness of about 0.008 inches. The same PNN + (or NPP +) junction can be formed in a flat wafer at a depth of about 3 μm to 10 μm. Subsequently, such PNN + wafers are stacked together with a thin layer of aluminum sandwiched between each wafer, and the PNN + junction and crystal orientation of each wafer can be oriented in the same direction. In addition, aluminum-silicon eutectic alloys can be used, or metals such as germanium and titanium, or metals having a thermal coefficient that substantially matches the thermal coefficient of silicon, such as molybdenum or tungsten. . The interface between the silicon wafer and the aluminum alloy can then be alloyed together (eg, further including a catalyst material) so that the stacked assemblies can be bonded together. It should be understood that other materials such as germanium and titanium can also be used. Similarly, an aluminum-silicon eutectic alloy can also be used. It should be further understood that the electrolyte should be selected such that it does not adversely affect the operation of the VMJ and / or cause adverse chemical reactions to the VMJ. It should be understood that the formation of various N + and P-type doping layers can be implemented as part of the cell unit, and such mechanisms are well within the scope of the present invention.

  FIG. 17 shows a further aspect of the present invention comprising a VMJ having a textured surface used for electrolysis. A schematic perspective view of a grooved surface 1700 is shown as part of a vertical multiple junction (VMJ) battery 1720 according to one aspect of the present invention. Such a mechanism of texturing 1700 allows refracted light to be directed away from the p + and n + diffusion doped regions while simultaneously producing the desired carriers. Thus, incident light can be refracted at a surface 1710 having a normal vector n. Such a surface 1710 may be parallel to the PN junction surface of the VMJ 1720 and include the cross-sectional configuration of the groove 1700. In other words, the orientation of the surface 1710 is substantially perpendicular to the direction in which the unit cells 1711, 1713, 1715 are stacked. Such a grooved surface can improve the efficiency of the electrolysis process.

  FIG. 18 shows an exemplary texture for carving a groove in the surface of a VMJ that receives light to electrolyze the electrolyte. Such a groove may be a cavity-shaped groove such as a “V” -shaped cross-sectional configuration having various angles θ (for example, 0 ° <θ <180 °) or a “U” -shaped cross-sectional configuration. Well, the plane including the cross-sectional configuration is substantially perpendicular to the direction in which the unit cells forming the VMJ are stacked and / or substantially parallel to the PN junction of the VMJ. It should be understood that the texturing 1810, 1820, 1830 for the VMJ of the present invention differs from the prior art for texture of conventional silicon photovoltaic cells in the PN junction orientation and / or interaction with incident light. For example, conventional silicon photovoltaic cells generally absorb light at longer wavelengths closer to the PN junction (located horizontally) in order to better collect carrier currents. Textured to tilt the penetration of the light, thus mitigating the lack of spectral response to longer wavelength light in the solar spectrum. In contrast, in a VMJ of the present invention that includes a vertical junction and already provides an improved spectral response to longer wavelength light in the solar spectrum, this is not necessary.

  Rather, one aspect for implementing the groove of FIG. 7 (eg, a V-shaped groove) is the surface of a conventional solar cell (with reduced texturing or with texturing where reflected or refracted light approaches the junction) In contrast, the bulk recombination loss is mitigated by reducing the bulk volume. Specifically, the VMJ cell shows better carrier current collection for both short-wavelength light and long-wavelength light, and the response to short-wavelength light is heavily doped on the top surface. The response to long wavelength light is due to the enhanced collection efficiency of the vertical junction. As another example, instead of the cavity shaped grooved texture of the present invention, other textures (eg, random, pyramid, dome and similar protruding configurations) are implemented as part of the VMJ. , Incident light is refracted in all directions and light is absorbed in the p + and n + diffusion regions, thus reducing efficiency. In addition, a reflective coating can be provided on the back of the VMJ cell to further enhance light absorption.

  In another aspect, the present invention provides an edge-illuminated structure or vertical junction that can produce substantially high power under photovoltaic cells, such as solar cells, particularly high intensity radiation levels. The present invention relates to improvement in performance of high-strength solar cells such as a vertical junction structure. Various designs of PV elements forming unit cells used to fabricate VMJ photovoltaic cells are described herein in units for reducing recombination loss of photogenerated carriers by patterned contacts. .

  The VMJ battery has an intrinsic theoretical limit efficiency of over 30% at 1000 suns intensity, so further performance improvement using experimental understanding and insights from computer simulation and modeling analysis Is possible. Conventional one-sun solar cells are easily modeled with good results using analytical equations, but edge-lit VMJs operating at high intensity Batteries are not, because at high strength, even secondary effects can have a substantial impact on the operating efficiency of the cell. While aspects or features of the present invention have been described with respect to solar cells, related advantages such as such aspects or features and reduced recombination loss of photogenerated carriers can be found in, for example, thermal photocells, or laser source photons. It can be used in other photovoltaic cells such as excited cells. Furthermore, embodiments of the present invention may be practiced with other classes of energy conversion batteries, such as betavoltaic cells.

  The physical properties of electron-hole carrier pairs generated in solar cells at high intensity include surface recombination velocity, carrier mobility and concentration, reverse saturation current of the emitter (eg diffusion), minority carrier lifetime, It is quite complex because many physical parameters act on it, including but not limited to band gap narrowing, built-in electrostatic fields, and various recombination mechanisms. Mobility decreases rapidly with increasing carrier density, and Auger recombination increases rapidly with strength as the third power of carrier density. In order to incorporate such aspects into VMJ solar cell performance modeling, computer simulations (e.g., computational numerical two-dimensional analysis of photogenerated carrier transport in semiconductors) can be used for vertical junction unit cells or PV devices. Insights can be provided to physical parameters when operating at high intensity or physical parameters for operating at high intensity. Such simulations provide analytical and design tools to understand potential sources of performance efficiency and improve the performance of VMJ cells at high strength. One conventional solar cell is easily modeled with good results using a simple analytical equation, but not an edge-lit VMJ photovoltaic cell operating at high illumination intensity. It should be understood that at high intensity, even secondary effects can have a dramatic impact on the operating efficiency of the cell.

  A VMJ unit cell in which recombination loss of photogenerated carriers occurs at a high intensity by calculation simulation based on a model that incorporates numerous semiconductor physics of contact-to-contact VMJ unit cells. A specific area within is revealed. At least some of these regions exhibit a complex loss mechanism that depends on strength. Computer simulation reveals regions within the PV device or VMJ unit cell that can be improved to reduce VMJ battery recombination loss and improve performance. Aspects of the invention provide such improvements.

  Series resistance is considered to be a significant problem in the design challenges associated with conventional concentrator solar cells. In this regard, VMJ photovoltaic cell designs that have shown that series resistance is not a problem even at a solar intensity of 2500 have proven to be exceptionally appropriate. However, in order to improve the efficiency of a VMJ photovoltaic cell for photovoltaic power concentrators operating near solar intensity 1000, in some circumstances it is advantageous to sacrifice the increased series resistance to reduce design simplicity. Can be.

  Designs for substantially higher intensity operation, such as solar intensity 2500, that can still operate the VMJ battery efficiently, are unlikely to contribute to any better overall performance or economic benefits. Nevertheless, it should be understood that optical components, structures, solar tracking, and thermal control can require substantially more demanding and expensive concentrator system engineering. Thus, the solar cell and the associated process aspects or features for its manufacture described in the present invention can improve the efficiency performance of high-strength VMJ cells operating in the solar intensity range of 1000 or higher. VMJ solar cells or other solar cells that take advantage of aspects of the present invention may include increased manufacturing efficiency and the possibility of increased series resistance for additional manufacturing processes and solar intensities in excess of 1000. Can be more cost-effective and feasible. The aspects or features described herein can provide a suitable engineering trade-off for making a photovoltaic concentrator system using solar cells or VMJ cells, which has lower dollar / watt performance. Utilizing aspects of the invention that are more feasible and more cost effective.

A solar intensity 500 of a conventional VMJ unit cell design, for example P + NN + slab with deep junctions, using realistic parameters for effective silicon processing (minority carrier lifetime, surface recombination velocity, etc.) Computer modeling analysis at higher intensities showed the following percentage of recombination loss for some specific areas: That is,
・ P + diffusion 22.7%
・ P + contact 5.3%
・ N + diffusion 32.8%
・ N + contact 11.4%
Therefore, this analysis shows that the heavily doped P + and N + diffusion emitter regions with metal contacts account for more than half of all recombination losses in the unit cells forming the VMJ solar cell, Also, the design suggests that the optimal diffuse N + emitter may be different from the optimal diffuse P + emitter due in part to differences in mobility. The relative magnitude of the recombination loss resulting from the N + and P + regions can be switched to an N + PP + unit cell or a P + NN + unit cell with a shallow P + N junction. In one aspect, the present invention is directed to reducing recombination losses in the aforementioned diffusion regions to improve the performance of VMJ batteries.

Long minority carrier lifetimes and low surface recombination rates have been successfully achieved in conventional VMJ cell development, with high strength, open-circuit voltage V _OC = 0.8 volts per unit cell junction. It was. V _OC is determined by the current generated by sunlight and the diffused emitter reverse saturation current (J ₀ ), and both P + N and NN + junctions present in the unit cell of the VMJ solar cell contribute to the open circuit voltage. The optimal junction from an electrical point of view is the minimum J ₀ using J ₀ = 1 × 10 ⁻¹³ Acm ⁻² , which is representative of high quality low reverse saturation current in diffusion junctions, Analysis has shown that a diffusion depth of about 3 μm to 10 μm is sufficient for both P + diffusion and N + diffusion, even when taking into account the infinite recombination velocity in the ohmic contacts.

  Even deep and gradual NN + diffusion profiles should yield a built-in electrostatic drift field that enhances minority carrier motion towards the junction barrier for the best collection and reduced recombination in this region, and computer simulations show that NN + Note that junction enhancement is not as effective at high strength, and it is clear that this may result in higher recombination in the N + region as shown above.

  Through experimentation and computational modeling and simulation, the primary area for improving performance is the reduction of recombination losses in the heavily doped P + and N + diffused metal contact regions of VMJ unit cells operating at high strength. It was discovered that A surface stabilized with high quality oxide can have a recombination rate of several centimeters per second, much lower than the recombination rate of metal contacts, and the drift electric field generated by the diffusion profile is also high. Considering that it is less effective in strength, aspects of the present invention result in reduced metal contact area and diffusion area due to patterned dielectric coatings of PV devices or VMJ unit cells, improving the performance of VMJ solar cells To do.

  With reference to the drawings, FIG. 19A shows a diagram 1900 of a photovoltaic element 1910 having a dielectric coating 1920 patterned between one of the surfaces of the PV element and a metal contact 1925. Note that the surfaces of PV element 1910, dielectric coating 1920, and metal contact 1925 are shown out of contact for clarity. However, in the solar cells discussed herein, such surfaces are in contact. The patterned dielectric coating 1920 is shown as a periodic array or a discrete elliptical region assembled in a grid. The PV element 1910 is generally an N-type slab semiconductor material, which includes Si, Ge, GaAs, InAs, or other Group III-V semiconductor compounds, and Group II-VI semiconductors. It is one of a compound, CuGaSe, CuInSe, and CuInGaSe. The slab has a doped P + diffusion region 1916 (labeled P +) on the first surface of the slab and a doped N + diffusion on the second surface substantially parallel to the first surface. Region 1914 (labeled N +) can be included. The thickness of the active PV element 1910 can afford to have an N-type (N) layer 1912 between the doped diffusion layers 1914 and 1916. The thickness of the diffusion layers 1914 and 1916 may range from 3 to 10 μm and is determined by the doping process used to introduce carriers into the slab of N-type material (eg, slab 1912). Inclusion of the doped diffusion layer can be accomplished by substantially any doping means such as techniques commonly used in semiconductor processes, dopant materials, and the like. The dopant material may include phosphorus and boron for N + and P + doping, respectively. For illustrative purposes, both the interface between the N + diffusion layer 1914 and the P + diffusion layer 1916 and the N-type (N) layer 1912 is idealized as a sharp boundary where the concentration changes sharply. Such an interface can be irregular in the mixed region between neutral and doped materials. The degree of mixing is defined at least in part by the mechanism or means used to create the doped diffusion region.

  Although aspects or features of the present invention are first shown with respect to an N-type slab of semiconductor material as a precursor of PV element 1910, such aspects or features are also initially intrinsic, eg, It can be implemented or achieved with a precursor of a nominally undoped PV element 1910. Further, in alternative or additional scenarios, a P-type precursor can be used, and the PV element 1910 can have a P + diffusion layer 1916 on and near the first surface of the slab, as previously described, and It can be a slab of P-type doped semiconductor material that can include an N + doped diffusion layer 1914 on and near the second surface substantially parallel to the first surface.

  In one aspect of the invention, the patterned dielectric coating 1920 reduces the formation of a metal diffusion doping layer interface (eg, a metal and N + layer 1914 interface) when the active PV element 1910 is metallized. The openings in the patterned dielectric coating are the areas where the metal and the diffusion doping layer form the interface. Since such an interface has a high recombination loss, thus reducing the contact of the metal diffusion doping layer mitigates the non-radiative loss of photogenerated carriers (eg, electrons and holes), resulting in the PV device 1910 Solar power generation efficiency is improved. Also, coating a PV device, such as 1910, with a dielectric material results in surface state passivation, thus reducing surface recombination losses. The patterning of the dielectric coating can be accomplished by photolithography techniques, or other techniques that allow controlled patterning of substantially dielectric surfaces, such as wet etching. Such photolithography techniques generally result in patterning through multiple processing steps of masking and removing the dielectric material in the dielectric coating. Alternatively or in addition, the patterning of the dielectric coating may be performed in a deposition technique such as chemical vapor deposition (CVD) in the presence of a mask that covers the deposited material to define a particular pattern. Such vapor phase coating and its modified plasma enhanced CVD (PECVD), molecular beam epitaxy (MBE) and the like can be achieved.

  It should be understood that the dielectric coating layer 1920 can incorporate a variety of planar coupling structures and configurations that provide electrical contact between the N + doping diffusion layer 1914 and the metal contact 1925. As previously indicated, in the example 1920 diagram, the dielectric coating 1920 employs a square lattice arrangement of ellipsoidal separated regions. Other gratings in the dielectric region can also be formed. Such lattices can include triangular lattices, monoclinic lattices, face centered tetragonal lattices, and the like. Alternative or additional features of a portion of the dielectric material in the patterned dielectric coating can include separate or combined stripes of dielectric material. Note that a patterned dielectric coating, such as coating 1920, may be disposed between the metal contact 1935 and the P + diffusion doped layer 1916 (see, eg, FIG. 19B). The location of the patterned dielectric coating 1920 is defined by a neutrally doped junction that causes a major loss of radiant intensity during operation in a solar concentrator or other solar-electrical energy conversion apparatus or device. For example, in a PV element 1910 (eg, P + NN + unit cell), N + diffusion region (or layer), and contact of the diffusion region with metal 1925 can result in substantially greater losses at high electromagnetic radiation intensity, and thus The patterned dielectric coating 1920 in the configuration shown in the 1900 diagram is particularly high strength, reduces recombination (eg, radiative and non-radiative) losses, and improves the performance of the PV element 1910 Therefore, it is the most inexpensive configuration.

  A substantially arbitrary pattern of dielectric material (eg, a disconnected array of openings such as spaces between dielectric elliptical regions in the dielectric coating 1920) can be used to form a single diffusion layer (eg, N + layer 1914). ) To reduce recombination loss, because metallization applied in a later step causes all or substantially all open contact areas to be reduced within the VMJ cell structure. It should be understood that when fully coupled to a planar unit cell, it can be guaranteed to be connected to each other. The unit cell used to make the VMJ photovoltaic cell described herein consists of a PV element 1910 that has been metallized coated with a pattern of derivatives, as previously described. Therefore, such unit cells are different from conventional unit cells used for the manufacture of conventional VMJ solar cells. A smaller contact area between the metal and the doped layer may contribute to an increase in series resistance in the stack, such as the PV element 1910 that forms the solar cell, thus reducing the contact area ratio. It is noted that an advantageous pattern to do is a high density of smaller apertures that are closely spaced to optimize performance for a given strength. Recombination loss can include heat dissipation or non-radiative recombination of photogenerated carriers, which can comprise Auger scattering, carrier-phonon relaxation, and the like. The rate of Auger recombination increases as the carrier density, eg, the cube of the density of photogenerated carriers, and doubling the volume of the photovoltaic device results in a recombination loss when most of the Auger scattering is the cause. May result in a 16-fold increase. Thus, a thinner slab 1910 or use of light capture using a textured surface, such as a V-shaped grooved surface, a U-shaped grooved surface,. . . Or any design modification that makes the PV element 1910 substantially thinner, such as a back reflector, alleviates most Auger recombination at high strength by reducing the thickness of the unit cell forming the VMJ photovoltaic cell Can be used for If a VMJ unit cell designed according to aspects described herein can reduce 50% of recombination loss, the collection efficiency of PV cells can be significantly improved.

  It should be understood that virtually any dielectric material can be used for the dielectric coating 1920. In one aspect, the dielectric coating may be a thermal oxide layer, which has a low surface recombination rate. To make an electrical contact at the end of a unit cell (or PV element) of a semiconductor-based (eg, Si-based) VMJ photovoltaic cell having an aperture patterned in the dielectric, the thermal expansion coefficient and thermal coefficient of the unit cell Requires a full electrical contact that can be provided by a low resistivity silicon that matches or substantially matches, or a metal such as molybdenum or tungsten that has a thermal coefficient that approximately matches that of silicon. It should be further understood that this is sometimes the case. Similarly, for VMJ solar cells based on semiconductor materials or compounds other than silicon, a patterned dielectric coating, such as 1920 or 1960 metallization, can be used to form a conductive material, such as a semiconductor material of a unit cell that forms a VMJ solar cell. This can be achieved with a low resistivity doped semiconductor having a thermal coefficient approximately equal to the thermal coefficient.

  With respect to the metal layer, the metal contact layer 1925 and the metal contact layer 1935 can be different. For example, to mitigate self-doping, the first metal contact layer (eg, layer 1925) can include a dopant, and the second contact layer (eg, layer 1935) can incorporate a diffusion barrier.

  FIG. 19B is a diagram 1950 of a photovoltaic element 1910 having a dielectric coating patterned in both diffusion doped regions. In FIG. 1950, a first patterned dielectric coating 1920 between the N + diffusion doping layer 1914 and the first metal contact 1925 and a second between the P + diffusion doping layer 1916 and the second metal contact 1935. A patterned dielectric coating 1960 is seen. The aspect of the dielectric coating 1960 is substantially the same as that of the dielectric coating 1920. As mentioned above, the metal contact layers 1925 and 1935 can be different.

  Mitigation of recombination loss of photogenerated carriers, and resulting performance improvement of PV devices, resulting from the introduction of the second patterned dielectric coating is related to the creation of the second patterned dielectric coating. Note that this adds to the complexity and the potential for additional processing costs.

  To ensure efficient operation of the PV element 1910 of the photovoltaic device, the first pattern in the dielectric coating 1920, the second pattern of the coating 1960, the one or more openings, the metal layer 1925, And the second pattern should be related to each other so that they have opposite pairs. When the patterned dielectric coating 1920 is “out-of-phase” with respect to the patterned dielectric coating 1960 and both derivative coatings occlude portions of the respective metal layer 1925 from each other, a stack of PV elements 1910 is formed. As a result, the resistance between the unit cells increases and the efficiency of the VMJ solar cell decreases.

  In addition or alternatively, the opening formed by the patterned dielectric coating 1920 may be different in size, eg, area, from the opening created by the dielectric coating 1960. For example, in order to reduce the total loss more effectively, especially when there is a larger loss between the N + diffusion region and the metal contact, in the PV element 1910 or the P + NN + unit cell, the opening area for N + contact is for P + contact It may be desirable to have a larger opening area. As mentioned above, such differences between aperture sizes can be implemented or utilized regardless of the specific pattern of the dielectric coating.

  FIG. 19C shows an example of a set of precursors and resulting PV devices that can be made by doping according to the embodiments described herein. As previously indicated, (i) an N-type doped precursor 1980 to produce a PV device that is treated to introduce the patterned dielectric coating and metal contacts described herein. Three precursor types can be used: (ii) P-type doped precursor 1985, and (iii) intrinsic precursor 1990. The precursor is a semiconductor material such as Si, Ge, GaAs, InAs, or other Group III-V semiconductor compound, Group II-VI semiconductor compound, CuGaSe, CuInSe, and CuInGaSe. Upon doping, an N-type precursor 1980 can provide a PV device 1982 that includes an N + type diffusion doped region and a P + type doped region, such a PV device being a PV device 1910. Also, doping the precursor 1980 can result in a PV device 1984 having N-type and P-type diffusion doped layers or regions. Precursor 1985 can form PV device 1986 having an N + diffusion doping layer and a P + diffusion doping layer, and PV device 1988 having an N + diffusion doping layer and a P-type doping layer. Various dopings of the intrinsic precursor 1990 result in PV elements 1992-1998. The PV device 1992 includes a P-type doping region and an N-type doping region, the PV device 1994 includes an N + -type doping layer and a P-type doping layer, and the PV device 1996 includes an N-type doping layer and a P + -type doping layer. The PV element 1998 includes an N + type doping layer and a P + type doping layer. Precursors 1980, 1985, and 1990 with various doping regions introduced are shown as extending regions, but are such regions spatially limited, as described herein? Or it can be almost limited. The various PV devices shown herein have been patterned as described herein to form unit cells that can be stacked to make a monolithic photovoltaic cell according to aspects of the invention. It can be coated with a dielectric material and metallized. In one aspect, patterned contacts formed by coating with P + NN + PV elements or unit cell patterned dielectric material can be used for terrestrial PV concentrators versus P + PN + PV elements. Or the unit cell is made more radiation resistant and is therefore utilized for space applications.

  FIG. 20A is a cross-sectional view 2000 of a PV device having one surface patterned with a dielectric coating. The pattern of dielectric material results in a portion of dielectric 2005 deposited on the N + diffusion doping layer 2014. Note that additional or alternative PV device configurations having a patterned dielectric coating on the P + diffusion doped layer 2016 are possible. In the PV device shown in FIG. 2000, diffusion doping regions 2014 and 2016 are separated by an N-type region 2012. As discussed above, such a configuration can be effective in mitigating recombination losses associated with PV element operation at high strength.

  FIG. 20B shows a view 2030 of the PV element when metallized with metal contacts 2025 and 2035. The presence of the patterned dielectric coating region 2005 on the N + diffusion layer 2014 reduces the electrical coupling between the electrical contacts 2025 and 2035. As discussed above, the metal contact layer can be different.

Figure 20C is a configuration unit cells _{(constituent unit cells) 2070 1 ~2070} M (M is a positive integer) shows an embodiment of a VMJ photovoltaic cell 2060 are stacked along the direction 2080, these are pieces On the side, an asymmetrically patterned dielectric coating on the N + diffusion doped layer (eg, a coating having a dielectric region 2005) is utilized. A VMJ solar cell obtained from a stack of unit cells 2070 _λ (λ = 1, 2,..., M), which is a PV element, is a monolithic (eg, integrally bonded) axially oriented structure. . In one aspect, two classes of VMJ photovoltaic cells (a) homogeneous and (b) heterogeneous can be formed based on the semiconductor material of the unit cell. In (a), unit cells 2070 _{1 to} 2070 _M are based on the same or substantially the same precursor, whereas in (b), the unit cells are based on different precursors. Different precursors may be based on the same semiconductor compound, for example, Si, Ge, GaAs, InAs, or other Group III-V semiconductor compounds, and Group II-VI semiconductor compounds CuGaSe, CuInSe, and CuInGaSe are different in doping type, or alloy compounds may have different alloying concentrations. Heterogeneous VMJ photovoltaic cells can utilize various portions of the emission spectrum of a source of electromagnetic radiation (eg, sunlight spectrum). The VMJ solar cell can generate a series voltage ΔV≈M · ΔV _C along the direction 2080, where ΔV _C is the voltage of the constituent PV element 2070 _λ . In one aspect, generally M-40 is utilized to form a VMJ solar cell. A 1 cm ² VMJ with M-40 can output approximately 25 volts under typical operating conditions such as incident photon flux, radiation wavelength, temperature. PV devices with poor performance are the bottleneck of current output in series connection, that is, current output is that of the worst performing unit cell, so the performance of PV device stacking is constrained by such devices I want you to understand. Therefore, to optimize performance, the active PV element stack or unit cell forming the VMJ photovoltaic cell is subject to conditions substantially similar to those expected under normal operating conditions of the solar collector system in the field. Based on the performance characterization performed on the test bench under (e.g., wavelength of radiation, concentrated intensity), the currents can be matched or nearly matched. The matched current is the current generated by solar-electric energy conversion by the PV element or unit cell.

Also, the monolithic stack of PV elements 2070 _{1 to} 2070 _M making a VMJ solar cell has a specific crystal plane with integer Miller indices q, r, s when the VMJ solar cell is part of a PV module or PV device. In order to expose (qrs) to sunlight or to be substantially exposed, for example, processing such as sawing, cutting, etching, and peeling can be performed. In one aspect, the specific crystal plane can be a plane (100) to achieve an intrinsic passivation of the surface state. FIG. 20D shows a PVJ element 2092 with patterned contacts as shown in FIG. 20C, or a VMJ PV cell 2090 produced by unit cell stacking, where the normal vector 2094 is oriented. It is processed so as to expose a specific crystal surface (qrs) which is shown oriented in <qrs>. It is noted that any PV device with patterned contacts as described herein can be utilized to form a VMJ PV cell that exposes the crystal plane (qrs). Also, as part of the process, the VMJ PV cell portion 2096 is removed based on the orientation <qrs> to create a flat surface that facilitates or enables the utilization of the VMJ PV cell of the PV device or module. can do.

FIG. 21A illustrates an exemplary dielectric coating pattern for a PV device. Patterns 2130 and 2140 correspond to patterns for the first and second surfaces of the PV element. The openings in the dielectric coating are lines or stripes having a defined width w 2135 and a pitch gap w _P 2145 between each other. In one aspect, such a structure of patterned dielectric coating openings results in a reduction of the contact area of (1 + w / w _P ) ⁻¹ , for example when w = w _P the reduction of the contact area is 50% It is. However, the smaller the contact area may contribute to an increase in series resistance, so the preferred line or stripe pattern to reduce the percentage of contact area is smaller, closely spaced High density openings in lines or stripes. This density can be varied to optimize the performance for a given radiation intensity at which the PV element is expected to operate as part of a PV module solar cell or PV cell. Additional or alternative patterns on the PV element 1910, or both opposing surfaces of the wafer, are possible and advantageous. As shown, lines or stripes, openings can be made on either side of each PV element 1910, or wafer, and can be offset 90 degrees from one side to the other, ie, patterned dielectric The stripes of the coating 2130 are oriented at an angle of 1935 degrees with respect to the <100> direction, while the stripes of the patterned dielectric coating 2140 are aligned at an angle of 45 degrees with respect to <100>. It is noted that other relative direction shifts are possible and advantageous. Further, as indicated above, the opening formed by the patterned dielectric coating 2130 may be different in size, eg, in area, from the opening created by the dielectric coating 2140. For example, in order to reduce the total loss more effectively, especially when there is a larger loss between the N + diffusion region and the metal contact, in the PV element having the P + NN + unit cell, the opening area for N + contact is for P + contact A wider area than the open area may generally be desirable. In an alternative, it may be desirable to implement the open area for the P + contact wider than that for the N + contact to mitigate the recombination loss of the N + PP + unit cell (eg, PV element 1986).

  In the manufacture of vertical multi-junction solar cells described herein, including the lamination and alloying of surface-patterned PV elements, they are defined when the differently oriented and dielectric regions are joined to the metallization. Low resistance contact points can be formed in the pattern. In one aspect, the contact points facilitated by the openings in the derivative coatings 2130 and 2140 are adjacent to each other in a controlled pattern in direct alignment to keep the series resistance of the finished VMJ cell low, and the P + of one wafer A contact connects at the point to the N + contact of the next wafer. As previously described, in one aspect, the fabricated VMJ cell is sawed to have a preferred crystallographic orientation <100> at the illuminated surface to establish a low level surface state for passivation. can do. Thus, as shown in FIG. 21A, the relative orientation of the line or stripe on the first surface of the patterned PV element is offset from the second surface line or stripe by an angle γ such as 90 degrees. The first and second surfaces may include a crystal orientation <100>, for example perpendicular to the crystal plane (100). Other orientations of lines or stripes are possible and advantageous. Similarly, relatively offset orientations γ of various surface lines or stripes can be implemented. In one aspect, the offset orientation γ is a finite real number, for example, dielectric coating patterns are not aligned on different surfaces. Further, the VMJ photovoltaic cell described herein can be treated to expose or substantially expose any crystal plane (qrs), and the dielectric coating stripes are q, r, and s. Can be oriented at an angle with respect to the crystal direction <qrs> having a Miller index of. Specifically, the patterned dielectric coating stripes on the first surface can include stripes oriented at a first angle α with respect to <qrs> while the second surface stripes of the second surface. The patterned dielectric coating stripes can be oriented at a second angle β (α ≠ β) with respect to <qrs>, thus resulting in an offset orientation γ = α−β.

  FIG. 21B shows a cross-sectional view of a PV device 2150 having a dielectric coating pattern deposited on both the P + diffusion doped layer 2176 and the N + diffusion doped layer 2174. FIG. In PV element 2150, diffusion doping regions 2014 and 2016 are separated by N-type region 2172. The cross section shown is a cut showing the alignment of a dielectric region (eg, dielectric region 2155) on the first surface with a dielectric region (eg, dielectric region 2165) on the second surface. It should be understood that other cross-sectional cuts may indicate the first and second surfaces that are misaligned regions of the dielectric material. As discussed above, such an alignment causes the metal contacts of the P + diffusion doping layer to be subsequently stacked when stacked to form a VMJ solar cell, as shown in FIG. 21C. Since the metal contacts of the layers can be matched, it is easy to maintain the series resistance between the PV elements 2150. As indicated above, it should be understood that the spacing of dielectric regions 2155 may be different from the spacing of dielectric regions 2165.

  FIG. 22 shows a cross-sectional view of an exemplary PV device 2200 having dielectric coating regions 2205 created by the deposition of a patterned dielectric coating 2202 so that when the PV device is metallized, its surface It becomes easier or possible to reduce at least one of the metal contact areas. In the PV device 2200, the N + diffusion region 2214 is configured to reduce the volume of the doping layer and thus mitigate recombination loss of photogenerated carriers. The region of N + doping can be determined by the patterned dielectric coating opening structure, for example, N + diffusion region 2214 is oriented along the pitch spacing of the striped pattern of dielectric coating 2202 It can be a stripe. Such a region is formed as a mask for controlling or manipulating N + doping by utilizing the dielectric coating region 2205. Based at least in part on the topology of the patterned dielectric coating 2202 and the deposited region 2205, the N + diffusion doping area or volume 2214 can be fully or pseudo limited, eg, no more than two It is restricted in direction (confine) and extends in the third direction. In the feature of the PV element 2200, the region of N-type material 2212 intersperse with the N + diffusion doped region 2214. Also, the P + diffusion doped region 2216 is not coated with a patterned dielectric material.

  When metallized, for example, the surface of the P + diffusion layer 2216 and the patterned surface of the confined and disconnected N + diffusion doped region (eg, a set of regions 2214) are coated with metal contacts, 1 A set of metallized PV elements can be stacked and soldered or alloyed by a process, such as a high temperature manufacturing step, to form a VMJ photovoltaic cell with reduced recombination loss according to aspects described herein. .

  FIG. 23A shows a cross-sectional view of a PV device 2300 having a dielectric coating pattern deposited on opposing diffusion doped regions. In one aspect, a first dielectric coating pattern (eg, a stripe pattern 2330 oriented along a direction rotated 135 degrees relative to the crystal direction <100>, the metal contact surface at the first diffusion doped region). While a second dielectric coating pattern (eg, a stripe pattern 2340 oriented at 45 degrees with respect to the crystallographic direction <100>). The N + diffusion doping region and the P + diffusion doping region can include doping regions 2314 and 2316 that are confined in more than one direction, respectively. The openings in the dielectric coating pattern can act as a mask to create a reduced volume doping diffusion layer, which are formed between the coated dielectric regions 2305 and 2325. Reducing the volume of the doped region of the metal contact surface and both diffusion doped layers can result in improved enhancement of mitigation of carrier recombination loss with respect to dielectric coating and doping volume reduction of one doping region. As discussed above, the improved PV performance benefits of patterned PV elements, or VMJs made with unit cells, outweigh the additional processing complexity and cost associated with surface patterning. Further, the opening formed by the patterned dielectric coating 2330 is different in size, eg, in area, from the opening produced by the dielectric coating 2340 to further control the recombination loss resulting from the diffusion doped region. It can happen. For example, in order to more effectively reduce the total loss, especially when there is a greater loss between the N + diffusion region and the metal contact, an opening that creates a larger N + doping region than an opening that creates a P + doping region. It may be desirable to increase it.

  FIG. 23B shows a cross-section of a patterned PV element 2350 having metal contact layers 2365 and 2375 that may be different from each other as discussed above. The cross-sectional cut shown is a metal region 2365 (eg, in the space of the dielectric material) on the surface of the N + diffusion doping layer aligned with a metal region 2375 (eg, a region between the spaces in the dielectric material) on the surface of the P + diffusion doping layer. Between). In the PV element 2350, a doping region is formed in the N-type precursor. A set of patterned PV elements 2350 can be stacked and processed to form a VMJ solar cell with improved performance.

FIG. 24 is a perspective view illustrating one embodiment of a textured vertical multi-junction (VMJ) photovoltaic cell 2405 having a textured surface, which shows unit cells 2410 _{1 to} 2410 ₁₀ on the surface of the unit cell. Each unit cell 2410 _κ (κ = 1, 2,..., 10) is formed by stacking along a direction perpendicular to each of the patterned dielectrics as described herein. It consists of a PV element with a coating and metal contacts. In this example, the textured PV cell 2405 is shown as a set of 10 unit cells, but a textured VMJ photovoltaic cell can comprise M unit cells, where M is a positive integer. It is noted that there is. A textured VMJ photovoltaic unit cell, eg, 2410 _κ , can be implemented with unit cells 2070 _λ , 2180 _λ , or 2350, or any other unit cell made as described herein. . In the photovoltaic cell 2405, the textured surface 2412 is the surface of a V-shaped groove, but other grooves such as U-shaped grooves or various shaped cavities can be formed. A textured surface is a surface (qrs) that is exposed or substantially exposed to electromagnetic radiation as a result of processing a monolithic stack of unit cells or PV elements having patterned metal contacts as described herein. ), See for example FIG. 20D. Incident light may be refracted at a surface 2430 having a normal vector n2432. Such surface 2430 is parallel to the surface patterned dielectric material of the unit cell 2410 _kappa is coated, can include a cross-sectional configuration of the groove 2415, to the direction of stacking the unit cell 2410 _kappa Is substantially vertical. Texturing the surface of the unit cell 2410 _kappa monolithic stack results in a textured surface 2412 so that the refracted light is away from the P + and N + diffusion doped regions without interfering with the carrier's photovoltaic power generation. Can be oriented, and thus the unit cells that make up the textured photovoltaic cell 2405 can be made thinner, and effectively reduce recombination loss as previously shown. Furthermore, an anti-reflective coating can be applied to the textured surface 2410 to increase the absorption of incident light in the battery.

  In view of the exemplary systems and elements described above, exemplary methods that can be implemented in accordance with the disclosed invention can be better understood with reference to the flowcharts of FIGS. For ease of explanation, the methods described herein are shown and described as a series of processes, although some processes are other processes shown and described herein. It should be understood that the invention as described and claimed is not limited by the order of processing, as they may be performed in a different order and / or simultaneously. For example, it should be understood that the methods described herein can alternatively be represented as a state or event having a series of interrelationships, such as in a state diagram or interaction diagram. Moreover, not all illustrated treatments may be required to implement an exemplary method in accordance with the specification of the present invention. Moreover, the exemplary methods described herein can be implemented in conjunction to achieve one or more features or advantages.

  FIG. 25 is a flow diagram illustrating an exemplary method 2500 for making a VMJ solar cell with reduced carrier recombination loss in accordance with aspects disclosed herein. The exemplary methods of the present invention are not limited to solar cells, and can be accomplished to make any or substantially any photovoltaic cell. One or more components or modules described herein may achieve the exemplary method 2500 of the present invention. At process 2510, a set of surfaces of a photovoltaic element (eg, PV element 1910) is patterned with a dielectric coating. Patterning a PV device with a dielectric coating includes utilizing any suitable technique to create one or more of the derivative coatings previously discussed. As an example, patterning can proceed by deposition and photolithography techniques. As another example, etching techniques can also be used to complement or supplement the employed patterning protocol. Virtually any or any dielectric material can be used to coat the surface set. At process 2520, metal contacts are deposited on one or more of the patterned surfaces of the PV element. Alternative or additional realizations of process 2530 can include depositing ohmic or conductive contacts on one or more patterned surfaces of the PV device. The material for the metal contact or ohmic contact can be implemented with virtually any or any conductive material, for example a low resistivity doped semiconductor or metal. In one aspect, the conductive material preferably has a thermal coefficient that approximately matches the thermal coefficient of the semiconductor material of the PV element. In another aspect, the conductive material has bonding properties that facilitate stacking of patterned and metallized PV elements. In yet another aspect, the pattern of dielectric material coating ensures that the metallization of the opposing surface results in a low resistance region by aligning metal regions on different surfaces (eg, The 90 ° offset stripe openings in patterns 2330 and 2340 result in metal contact regions aligned along the stacking direction (eg, z-direction 2080). At process 2530, a set of patterned and metallized photovoltaic elements are stacked to form a VMJ solar cell. It should be understood that such PV devices can include a confined diffusion doped region, as discussed above. At process 2540, the formed VMJ solar cell is processed to facilitate placement within the PV device, to optimize photovoltaic performance, or a combination thereof. Such processes may include various manufacturing steps or processes such as a cutting process, a polishing process, a cleaning process, an integrated process, and the like. Such a treatment can be directed at least in part to exposing a particular crystal plane to sunlight when the formed VMJ solar cell is placed in a PV device. In one example, the process is a cutting formed VMJ cell (cutting formed to expose or substantially expose crystal plane <100> to sunlight in order to establish the lowest quality surface state for passivation. VMJ cell).

  FIG. 26 is a flow diagram illustrating an exemplary method 2600 for making a solar cell with reduced carrier recombination losses in accordance with aspects described herein. The exemplary method 2600 of the present invention is not limited to the manufacture of solar cells, and the exemplary method 2600 can also be accomplished to make any or substantially any photovoltaic cell. One or more components or modules described herein may achieve the exemplary method 2600 of the present invention. In process 2610, a set of surfaces of a photovoltaic element (eg, PV element 1910) is patterned with a dielectric coating. Patterning a PV device with a dielectric coating includes utilizing any suitable technique to create one or more of the derivative coatings previously discussed. As an example, patterning can proceed by deposition and photolithography techniques. As another example, etching techniques can also be used to complement or supplement the employed patterning protocol. Virtually any or any dielectric material can be used to coat the surface set. At process 2620, the patterned dielectric coating can be utilized to create a confined diffusion doped region in the PV device. The patterned dielectric coating can be used as a mask to define the degree of doping region confinement. In one aspect, the doping region limitation may be approximately two-dimensional, and the doping may extend substantially along one dimension and be limited along two different directions. The doping region limitation may be approximately three dimensional, and the doping of the PV device is limited to a set of one or more local regions that are substantially smaller than the size of the PV device (see, eg, FIG. 22). I want to be) As an example, when a stripe pattern of dielectric material (eg, pattern 2330) is utilized as a doping mask, for example, the diffusion direction toward the center of the slab of nominally undoped semiconductor material, and the pitch in the patterned coating Or a diffusion doped layer can be provided that is substantially limited in two directions, such as the direction perpendicular to the stripe. The limited region of the diffusion doped region is reduced in volume and the photogenerated carrier recombination loss is mitigated.

  At operation 2630, ohmic contacts are deposited on the patterned surface of the one or more PV elements. The material for the ohmic contact can be implemented with virtually any or any conductive material, for example a low resistivity doped semiconductor or metal. In one aspect, the conductive material is a semiconductor material for PV devices, such as Si, Ge, GaAs, InAs, or other Group III-V semiconductor compounds, Group II-VI semiconductor compounds, and CuGaSe. CuInSe, CuInGaSe,. . . , And the thermal coefficients almost coincide with each other and are suitable for alloying. As previously indicated, the pattern of dielectric material coating results in a region of low electrical resistance, with the deposition of ohmic contacts on opposite patterned surfaces aligning the metallization regions on different surfaces (Eg, openings with stripes in 90 ° offset directions in patterns 2330 and 2340 result in metal contact regions aligned along the stacking direction (eg, z-direction 2080)).

  In process 2640, a set of patterned metallized photovoltaic elements are stacked to form a solar cell. The set of photovoltaic elements forming the solar cell spans M elements, where M is a natural number determined at least in part by the target operating voltage of the solar cell. In one aspect, the set of PV elements can be homogeneous or heterogeneous. In a homogeneous set, each element or unit cell in the set is based on the same or substantially the same precursor, and in a heterogeneous set, each element is based on a different precursor. Different precursors may be based on the same semiconductor compound, for example, Si, Ge, GaAs, InAs, or other Group III-V semiconductor compounds, and Group II-VI semiconductor compounds CuGaSe, CuInSe, and CuInGaSe are different in doping type, or alloy compounds may have different alloying concentrations. Such patterned and metallized PV devices also include limited diffusion doped regions, as discussed above. At 2650, the solar cells are processed to facilitate placement within the PV device, to optimize photovoltaic performance, or a combination thereof. The process can include various manufacturing steps or processes such as a cutting process, a polishing process, a cleaning process, an integrated process, and the like. Such a step can be at least partially intended to expose a particular crystal plane to sunlight when the formed solar cell is placed in a PV device. In one example, the process comprises a solar cell that has been cut to expose or substantially expose the crystal plane (100) to sunlight in order to establish the lowest grade surface state for passivation. . It should be understood that the solar cell can be processed to expose or substantially expose other crystal planes, for example (qrs) planes such as (311).

  FIG. 27 is a block diagram of an example system 2700 that enables manufacturing of a solar cell according to aspects described herein. A deposition reactor 2710 may be used to process semiconductor-based wafers, as described herein, to produce PV elements or unit cells that constitute solar cells, eg, VMJ solar cells. it can. The deposition reactor 2710 and the modules therein include various hardware components, software components, or combinations thereof, and associated electrical or electronic circuitry for accomplishing the process. In an aspect, the coating module 2712 can pattern the surface of a semiconductor wafer or substrate using a dielectric coating. The wafer or substrate may be nominally undoped or doped and is a precursor for PV devices used in the manufacture of solar cells. As indicated above, patterning may be based on the deposition of dielectric material by appropriate mask, photolithography, or etching. The deposition reactor 2710 also includes a doping module 2714 that allows the dopant to be included in the semiconductor precursor of the PV device. As described above, the dopant can form a diffusion doped layer (see, eg, FIG. 19 or FIG. 23), but the doping module 2714 can be used with any optional, such as substantially epitaxy-based doping, such as delta doping. It also provides a type of doping. Also, the doping module 2714 allows the formation of a diffusion barrier that can prevent self-doping.

  As described above, the coating of the PV element with the dielectric material can be performed before or after doping. Doping that follows the patterned dielectric coating utilizes such a coating as a mask to create a limited or nearly limited doping region (see, eg, FIG. 22).

  The metallization module 2716 allows the deposition of a metal layer on a PV device that includes an extended or limited doping region and a patterned dielectric coating. Metallization can be achieved by deposition of semiconductor material or metal material with subsequent doping. In one aspect, such a material has a thermal coefficient that matches or substantially matches that of a PV device having a doped region.

  The deposition reactor 2710 includes a sputtering chamber, an epitaxy chamber, a vapor deposition chamber, an electron beam gun, a raw material holder, a wafer storage location, a sample substrate, an oven, and a turbo molecular pump, a diffusion pump, etc. Vacuum pumps. The deposition reactor 2710 can also include a computer including a processor and volatile or non-volatile memory, a programmable logic controller, and a dedicated processor such as a special purpose chipset. The deposition reactor 2710 can also include a software application, such as an operating system, or code instructions to accomplish one or more processing operations including at least those previously described. The described hardware, software, or combination thereof facilitates or enables at least a portion of the functionality of the deposition reactor 2710 and its modules. Bus 2718 allows information to be communicated between various hardware, software, or combinations thereof within deposition reactor 2710, such as data or code instructions, material transfer, processed element exchange, and the like. .

  The photovoltaic elements can be supplied to a package platform 2730 for further processing. An exchange link, for example a conveyor link, or an exchange chamber and its electromechanical components can supply PV elements, at least one of the exchange links or the exchange chamber being indicated by arrow 2720. The assembly module 2732 can collect a set of PV elements to make a solar cell, eg, a VMJ solar cell, allowing each of the PV elements to be stacked by a high temperature process or step. The stack is transferred to a standard module 2734 that completes the solar cell to a defined standard, for example, the stack may be exposed to specific crystal planes of the PV elements of the stack forming the solar cell. Processed. Such processing can be facilitated or enabled at least in part by a test module 2760 that can determine the crystal orientation of the PV elements or unit cells in the solar cell, and such indexing can be X-ray spectroscopy, such as diffraction spectra and rocking curve spectra.

  To ensure quality or meet specifications, the test module 2760 can examine precursor materials or processed materials at various stages of solar cell manufacturing. As an example, test module 2760 may determine whether the density of the patterned dielectric coating openings in the PV element is appropriate for the expected solar intensity in the solar concentrator, or for photon flux. The density can be investigated. As another example, the test module can determine the density of defects that can arise from the thermal cycle of a PV element having a metal layer to verify that the material or process utilized for metallization is appropriate. . For at least such purposes, does the test module 2760 perform minority carrier lifetime measurements, X-ray spectroscopy, scanning electron microscopy, tunneling electron microscopy, tunnel scanning microscopy, electron energy loss spectroscopy, etc. Or you can make it possible. The investigation performed by the test module 2760 can be in situ or ex situ. Samples of processed material precursors or devices such as solar cells may be fed to the test module via exchange links 2740 and 2750.

  A processing unit (not shown) may achieve logic to control at least a portion of the various processes described herein in connection with the operation of system 2700. Such a processing unit (not shown) may include a processor that executes code instructions that achieve control logic, for example, code instructions such as program modules or software applications may be operatively coupled to a processor. (Not shown).

  What has been described above includes examples of systems and methods that provide the advantages of the present invention. Of course, it is not possible to describe every possible combination of components or methods for purposes of describing the present invention, but those skilled in the art will be able to do many additional combinations and permutations of the claimed subject matter. I can understand that. Further, as long as the terms “include”, “has”, “possess” and the like are used in the detailed description, claims, appendix and figures, such terms are “ It is intended to be as inclusive as the term “comprising”, as “comprising” is construed when used in the claims as a transitional word.

Claims (44)

A monolithic stack of a plurality of semiconductor-based photovoltaic (PV) elements, wherein each element of the plurality of semiconductor-based PV elements includes at least one of a P-type diffusion doping region or an N-type diffusion doping region (Monolithic stack)
A dielectric coating deposited and patterned on at least one of the P-type diffusion doping region or the N-type diffusion doping region;
And a metal layer at a boundary surface between the plurality of semiconductor-based PV elements.   The photovoltaic cell of claim 1, wherein at least one of the P-type diffusion doping region or the N-type diffusion doping region includes one or more confined regions.   The photovoltaic cell of claim 2, wherein the patterned dielectric coating comprises at least one of a disconnected region of dielectric material or a connected region of dielectric material.   4. The photovoltaic cell of claim 3, wherein the combined region of dielectric material includes at least one of a periodic lattice of dielectric regions or a nearly-periodic lattice.   The isolated regions of the dielectric material include a set of stripes oriented at a first angle relative to a <qrs> crystal direction or a set of stripes oriented at a second angle from a crystal direction of <qrs>. The photovoltaic cell of claim 3 comprising at least one, wherein q, r, and s are Miller indices.   The photovoltaic cell of claim 5, wherein at least one stripe density of the stripe set is defined at least in part by a radiation intensity at which the plurality of semiconductor-based PV devices are expected to operate. The first diffusion doping layer in the PV device is coated with a first pattern of dielectric material;
6. The photovoltaic cell of claim 5, wherein the second diffusion doping layer in the PV device is coated with a second pattern of dielectric material.   The photovoltaic cell of claim 7, wherein the first pattern of dielectric material is determined at least in part by a recombination loss mechanism of the first diffusion doping layer.   The photovoltaic cell of claim 8, wherein the second pattern of dielectric material is determined at least in part by a recombination loss mechanism of the second diffusion doping layer.   The photovoltaic cell of claim 1, wherein the stack of the plurality of semiconductor-based photovoltaic (PV) elements is processed to substantially expose a particular crystal plane to sunlight.   The photovoltaic cell according to claim 1, wherein the metal layer has a thermal expansion coefficient that substantially matches a thermal expansion coefficient of the semiconductor material of the photovoltaic power generation element.   The photovoltaic cell of claim 1, wherein the current outputs upon energy conversion supplied by the plurality of semiconductor-based photovoltaic (PV) elements substantially match.   The photovoltaic cell of claim 1, wherein each element of the plurality of semiconductor-based PV elements is formed by doping one of an N-type semiconductor precursor, a P-type semiconductor precursor, or an intrinsic semiconductor precursor.   The photovoltaic cell of claim 1, wherein the surface of the monolithic stack includes a textured surface having a pattern of cavity structures. A method of manufacturing a photovoltaic cell with reduced recombination loss of photogenerated carriers, the method comprising:
Patterning a set of surfaces of a photovoltaic (PV) device having a dielectric coating;
Depositing ohmic contacts on one or more of the patterned surfaces of the PV element;
Stacking patterned PV device sets having ohmic contacts to form a vertical multi-junction (VMJ) photovoltaic cell;
Treating the formed VMJ photovoltaic cell to facilitate placement within a PV device, to optimize photovoltaic performance, or a combination thereof.   16. The method of claim 15, wherein one or more surfaces in the set of surfaces includes a diffusion doping layer that extends over an extended region or a confined region. Using a patterned dielectric coating as a mask in the photovoltaic device to produce confined regions of diffusion doping;
16. The method of claim 15, further comprising:   The method of claim 15, wherein the material for the ohmic contact is a conductive material having a photovoltaic (PV) thermal expansion coefficient that substantially matches the thermal expansion coefficient of the photovoltaic element.   Patterning a set of photovoltaic (PV) device surfaces having a dielectric coating comprises a set of stripes oriented at a first angle relative to a <qrs> crystallographic direction of the PV device or the PV device. 16. The method of claim 15, comprising depositing at least one of a set of stripes oriented at a second angle from a <qrs> crystallographic direction, wherein q, r, and s are Miller indices.   20. The method of claim 19, wherein at least one stripe density of the stripe set is defined at least in part by the radiation intensity at which the plurality of semiconductor-based PV devices are expected to operate.   The processing operation includes cutting the formed VMJ photovoltaic cell so that the (qrs) crystal plane is substantially exposed to sunlight, and q, r, and s are Miller indices. Item 15. The method according to Item 15.   The method of claim 15, wherein the stack of patterned PV elements with ohmic contacts forming the VMJ photovoltaic cell is current matched. Means for patterning a set of surfaces of a photovoltaic (PV) device having a dielectric coating;
Means for depositing metal contacts on one or more of the patterned surfaces of the PV element;
Means for stacking a set of patterned PV elements having metal contacts to form a vertical multi-junction (VMJ) photovoltaic cell;
Means for processing the formed VMJ photovoltaic cells to facilitate placement in a PV device, to optimize photovoltaic performance, or a combination thereof.   24. The apparatus of claim 23, further comprising means for utilizing a patterned dielectric coating as a mask to create a diffusion doped confined region in the photovoltaic device.   25. The apparatus of claim 24, further comprising means for investigating at least one of a PV element, a PV element having a dielectric coating, a PV element having a metal contact, or a formed VMJ photovoltaic cell. A vertical multi junction (VMJ) photovoltaic cell comprising a plurality of integrally bonded cell units stacked along the stacking direction;
A photocell comprising: the VMJ surface for receiving light, textured to mitigate bulk recombination losses of the VMJ.   27. The VMJ photovoltaic cell of claim 26, wherein the stacking direction is substantially perpendicular to a plane across the textured surface to produce a substantially repeating cross-sectional pattern.   27. The VMJ photovoltaic cell of claim 26, wherein the substrate further comprises a "built-in" electrostatic drift field that promotes minority carrier motion of the PN junction. Integrating and bonding a plurality of active layers to form a VMJ battery;
A method of manufacturing a VMJ comprising: mitigating bulk loss in the VMJ battery by a textured surface of the VMJ that receives incident light. 30. The method of claim 29, further comprising refracting incident light at a plane parallel to the PN junction of the VMJ cell. Means for improving the spectral response to wavelength in a photovoltaic cell;
Means for mitigating bulk coupling losses for the photovoltaic cell. A vertical multi junction (VMJ) photovoltaic cell comprising a plurality of integrally bonded cell units, each having a plurality of layers forming a PN junction;
A photovoltaic cell comprising: a buffer zone that protects the plurality of layers from at least one of stress and strain induced on the VMJ photovoltaic cell.   33. The photovoltaic cell of claim 32, wherein the buffer zone can be implemented as a rim formation on the surface of the final layer of the cell unit.   33. The photovoltaic cell of claim 32, wherein the buffer layer comprises a substantially highly doped low resistivity silicon layer. Forming a VMJ battery by integrally bonding a plurality of active layers;
Protecting the active layer of the VMJ cell through at least one of stress, shear, moment and torsion induced to the VMJ cell via the buffer zone. 36. The method of claim 35, further comprising forming a buffer zone having a substantially low resistivity as part of an end layer of the VMJ cell. 36. The method of claim 35, further comprising incorporating ohmic contacts between outer layers of the unit cell. Means for forming a PN junction in a vertical multi junction (VMJ) photovoltaic cell;
Means for protecting a plurality of active layers from stress or strain induced on the VMJ photovoltaic cell. A vertical multi junction (VMJ) photovoltaic cell comprising a plurality of integrally bonded cell units, each having a plurality of layers forming a PN junction;
An electrolytic solution that receives an electric current generated by the VMJ photovoltaic cell, wherein the electric current decomposes the electrolytic solution.   40. The electrolysis system of claim 39, wherein the VMJ photovoltaic cell has a grooved surface. Integrating and bonding a plurality of active layers to form a VMJ battery;
Generating an electric current for electrolyzing the electrolytic solution from the VMJ battery. 42. The method of claim 41, further comprising cooling the VMJ battery with a thermal conditioning assembly. 42. The method of claim 41, further comprising forming a plurality of anodes and cathodes on a surface of the VMJ cell. Decomposition means for decomposing the electrolyte solution by incident light;
An electrolysis system comprising: means for cooling the decomposition means.

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