WO2003054926A2 - Appareil et procede d'integration d'une diode en parallele dans des cellules solaires - Google Patents

Appareil et procede d'integration d'une diode en parallele dans des cellules solaires Download PDF

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Publication number
WO2003054926A2
WO2003054926A2 PCT/US2002/034416 US0234416W WO03054926A2 WO 2003054926 A2 WO2003054926 A2 WO 2003054926A2 US 0234416 W US0234416 W US 0234416W WO 03054926 A2 WO03054926 A2 WO 03054926A2
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WIPO (PCT)
Prior art keywords
layer
solar cell
bypass diode
deposited over
doped
Prior art date
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PCT/US2002/034416
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English (en)
Other versions
WO2003054926A3 (fr
Inventor
Paul R. Sharps
Daniel J. Aiken
Doug Collins
Mark A. Stan
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Emcore Corporation
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Publication date
Priority claimed from US09/999,598 external-priority patent/US6680432B2/en
Application filed by Emcore Corporation filed Critical Emcore Corporation
Priority to AU2002365270A priority Critical patent/AU2002365270A1/en
Priority to JP2003555555A priority patent/JP4119844B2/ja
Priority to EP02805514A priority patent/EP1440480B1/fr
Priority to DE60229279T priority patent/DE60229279D1/de
Priority to DE10297371T priority patent/DE10297371T5/de
Publication of WO2003054926A2 publication Critical patent/WO2003054926A2/fr
Publication of WO2003054926A3 publication Critical patent/WO2003054926A3/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • H01L31/0687—Multiple junction or tandem solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/044—PV modules or arrays of single PV cells including bypass diodes
    • H01L31/0443—PV modules or arrays of single PV cells including bypass diodes comprising bypass diodes integrated or directly associated with the devices, e.g. bypass diodes integrated or formed in or on the same substrate as the photovoltaic cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • H01L31/0687—Multiple junction or tandem solar cells
    • H01L31/06875—Multiple junction or tandem solar cells inverted grown metamorphic [IMM] multiple junction solar cells, e.g. III-V compounds inverted metamorphic multi-junction cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1852—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising a growth substrate not being an AIIIBV compound
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/544—Solar cells from Group III-V materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • the present invention relates to the field of semiconductor devices. More specifically, the present invention relates to the photovoltaic solar cells.
  • Photovoltaic cells also called solar cells
  • solar cells are one of the most important new energy sources that have become available in the past several years. Considerable effort has gone into solar cell development. As a result, solar cells are currently being used in a number of commercial and consumer-oriented applications. While significant progress has been made in this area, the requirement for solar cells to meet the needs of more sophisticated applications has not kept pace with demand. Applications such as satellites used in mobile and telephone communications have dramatically increased the demand for solar cells with improved power and energy conversion characteristics.
  • the size, mass, and cost of a satellite power system are dependent on the power and energy conversion efficiency of the solar cells used. Putting it another way, the size of the payload and the availability of on-board services are proportional to the amount of power provided.
  • solar cells which act as the power conversion devices for the on-board power systems, become increasingly more important.
  • Solar cells are often used in arrays, an assembly of solar cells connected together in a series.
  • the shape and structure of an array, as well as the number of cells it contains, are determined in part by the desired output voltage and current.
  • each cell When solar cells in an array are receiving sunlight or are illuminated, each cell will be forward biased. However, if any of the cells are not illuminated, because of shadowing or damage, those shadowed cells may be forced to become reversed biased in order to carry the current generated by the illuminated cells. This reverse biasing can degrade the cells and can ultimately render the cells inoperable.
  • a diode structure is often implemented. The purpose of the bypass diode is to draw the current away from the shadowed or damaged cell. The bypass becomes forward biased when the shadowed cell becomes reverse biased. Rather than forcing current through the shadowed cell, the diode draws the current away from the shadowed cell and maintains the connection to the next cell.
  • a conventional bypass diode is typically connected to the exterior of a solar cell array. A problem associated with this type of bypass diode is that it is difficult to manufacture and also less reliable because the exterior assembly is performed by the array assemblers rather than the cell manufacturer.
  • Another conventional method for protecting the solar cell is to place a bypass diode between adjacent cells wherein the anode of the bypass diode is connected to one cell and the cathode of the diode is connected to an adjoining cell.
  • a problem associated with this technique is that it complicates the manufacturing process and is more difficult to assemble the solar cell array.
  • a third technique for protecting the solar cell involves forming a recess on the solar cell structure and placing a bypass diode in the recess. Because of the fragility of the cells this technique is difficult to implement in a manufacturing line. In addition, the adjoining cells need to be connected to the diode by the array assembler.
  • a solar device having a multijunction solar cell structure with a bypass diode is disclosed.
  • the bypass diode provides a reverse bias protection for the multijunction solar cell structure.
  • the multijunction solar cell structure includes a substrate, a bottom cell, a middle cell, a top cell, a bypass diode, a lateral conduction layer, and a shunt.
  • the lateral conduction layer is deposited over the top cell.
  • the bypass diode is deposited over the lateral conduction layer.
  • One side of the shunt is connected to the substrate and another side of the shunt is connected to the lateral conduction layer.
  • the bypass diode contains an i-layer to enhance the diode performance.
  • FIG. 1 illustrates one embodiment of the present invention, a multijunction solar cell, after the completion of all processing steps, illustrating the composition of such embodiment
  • FIG. 2 illustrates the two paths current in the cell illustrated in FIG. 1 can take, given a particular set of circumstances
  • FIG. 3 illustrates one embodiment of the present invention, a multijunction solar cell, prior to any processing steps
  • FIG.4 illustrates a first processing step used to construct one embodiment of the present invention
  • FIG. 5 illustrates the second and third processing steps used to construct one embodiment of the present invention
  • FIG. 6 is a block diagram illustrating a schematic sectional view showing a multijunction solar cell structure having a bypass diode in accordance with one embodiment of the present invention
  • FIG. 7 is a logic diagram illustrating a triple junction solar cell structure and a bypass diode in accordance with one embodiment of the present invention.
  • FIG. 8 is a block diagram illustrating a detailed schematic sectional view showing a triple junction solar cell structure having a bypass diode and a shunt in accordance with one embodiment of the present invention
  • FIG. 9A-9E are block diagrams illustrating a process of manufacturing a multijunction solar cell structure with a bypass diode and a shunt in accordance with one embodiment of the present invention.
  • FIG. 10 is a flow chart illustrating a method of manufacturing a multijunction solar cell structure with a bypass diode in accordance with one embodiment of the present invention.
  • a method and an apparatus of solar cell with multijunction solar cell structure having a bypass diode with an i-layer are described.
  • the present invention may contain transistor circuits that are readily manufacturable using well-known CMOS ("complementary metal-oxide semiconductor) technology, or other semiconductor manufacturing processes.
  • CMOS complementary metal-oxide semiconductor
  • the present invention may be implemented with other manufacturing processes for making digital devices.
  • the present invention relates to a multijunction solar cell with at least one integral monolithic bypass diode.
  • the layers comprising the solar cell are particularly chosen for their combination of efficiency and manufacturabili ⁇ y.
  • one embodiment consists of a multijunction structure with at least three junctions, with a unique modified buffer structure.
  • the process of manufacturing the solar cell with an integral monolithic bypass diode is comprised of five distinct steps, which are described below.
  • FIG. 1 is an illustration of an embodiment of the invention, a monolithic solar cell with an integral bypass diode.
  • FIG. 2 is a series of schematic drawings of the two possible current paths through the cell.
  • FIG. 1 shows a multijunction solar cell 100 with a cell of Indium Gallium Phosphorus (InGaP) 101 and a cell of Gallium Arsenide (GaAs) 102 over a GaAs buffer 103 on top of a Germanium (Ge) substrate 104.
  • InGaP Indium Gallium Phosphorus
  • GaAs Gallium Arsenide
  • FIG. 2 A represents the solar cell as seen in FIG. 4, without the metalization 107 and lateral conduction layer 113 described below. If the solar cell is illuminated, there will be no barrier to the current following the cell path 201 through the layers of the solar cell: the Ge junction 104, the GaAs junction 102, and the InGaP junction 101.
  • the cell contains a diode, however, the current can be offered an alternate, parallel path 202, and the shaded cells will be preserved.
  • the problem with this concept has been the difficulty in creating a diode that is relatively easy to manufacture and which uses a very low level of voltage to turn on and operate.
  • the invention described herein solves these problems.
  • the turn on voltage for the diode path 202 must be less than the breakdown voltage along the cell path 201.
  • the breakdown voltage along the cell path will typically be at least five volts, if not more.
  • the Schottky contact 403 requires a relatively small amount of voltage to "turn on" - 600 milivolts.
  • the bias of the Ge junction 104 must be reversed, requiring a large voltage. Reversing the bias of the Ge junction 104 requires approximately 9.4 volts, so nearly ten volts are needed for the cu ⁇ ent to follow the diode path 202 in FIG. 2A.
  • Gold (TiAu) contacts 109, 110 are added to the solar cell, an additional layer of metal 107 is added as well.
  • the metal is TiAu, although practitioners in the art will be well aware that other metals can also be used.
  • the effect of the metal 107 is to "short" the Ge junction 104 to the base of the Ge cell 104. Because of the short, a minimal voltage is required to pass current between the layer 113 and the Ge substrate. No longer is a high voltage required to force the current through the Ge junction 104. The cu ⁇ ent flows easily through the "short path" 107.
  • FIG. 2B provides a schematic representation.
  • the solar cell If the solar cell is shaded, no longer is the cell forced into reverse bias to pass the cu ⁇ ent of the a ⁇ ay string. There is a much less resistive path, requiring a much lower voltage drop, for the cu ⁇ ent to pass through the bypass diode 202. With the addition of the metalization 107, the Ge cell 104 is shorted. As a result, rather than a reverse biased diode with a 9.4 turn-on voltage, the cu ⁇ ent instead encounters an ohmic resistance path represented by the resistor 204.
  • the layer is doped to about 7 to 8 times 10 cm to do two things. First, it reduces the contact resistance of the metal layer 107 and second, it provides a low resistance path for the lateral conduction layer. Without the lateral conduction layer, the resistance at the resistor 204 is approximately 20 ohms. 20 ohms represents a significant drain on the cu ⁇ ent of the solar cell. To reduce this resistance, a lateral conduction layer 113 is added to the solar cell.
  • FIG. 2C represents the cu ⁇ ent paths in the solar cell as depicted in FIG. 1. When the solar cell is shaded, the cu ⁇ ent will flow to the resistor 204.
  • FIG. 3 shows a multijunction solar cell 100 and the component parts: the multijunction structure 301 and the buffer structure 302.
  • a top cell comprised of an n-on-p InGaP2 101 is grown over a cell of n-on-p GaAs 102.
  • a third diffused Ge junction 104 is formed due to diffusion of As during the growth of buffer layers 103.
  • a buffer exists between the upper junctions in the solar cell and the Ge substrate
  • the buffer layer is inserted in the manufacture process; normally it is a thick layer of GaAs grown over the Ge substrate.
  • the buffer structure 302 is comprised of the following: an InGaP Schottky contact
  • the buffer structure 302 is also comprised of an additional etch stop 304.
  • the etch stop 304 is also comprised of
  • the etch stop creates barriers during processing which facilitate formation of the bypass diode.
  • the lateral conduction layer 113 exists in this buffer layer, to more efficiently guide the cu ⁇ ent out of the diode, as discussed above.
  • the first step in the manufacturing process is to make a "wet etch" that comes down into the cell 100 and terminates at the InGaP layer 403.
  • a TiAu contact 110 is formed upon the InGaP layer 403.
  • a TiAu contact 109 is formed at the top of the cell to make an ohmic contact with the n -GaAs layer 112.
  • TiAu contact 110 on the InGaP layer 403 makes a Schottky contact, which is non-ohmic.
  • FIG. 5 shows a "mesa etch" 501 down to the level of the Ge cell 104.
  • the primary purpose of this step is to create a true diode 106, electrically isolating the junctions 105 within the solar cell from the diode 106.
  • the third step is a "shunt etch" 502, which provides a "shelf on which the metal
  • the etch stop 304 allows the solar cell to be manufactured more efficiently.
  • the fourth step is the metalization process.
  • the TiAu contacts 109, 110 are added, and the metal layer 107 is added.
  • the metal comprising the layer is TiAu.
  • the TiAu contact 110 meets the InGaP layer 403, a Schottky contact is created.
  • the TiAu contact 109 on top of the cell the TiAu makes an ohmic contact to n- type GaAs 112.
  • the etch stop at the GaAs buffer contact 304 alleviates this problem.
  • the GaAs buffer contact 113 is n+ doped at the same level as the GaAs buffer contact 112 at the top of the cell. This creates a cell with the same quality of contact between the TiAu contact 109 and the GaAs contact layer 112 at the top of the cell as the metal contact 107 with the GaAs layer 113.
  • Modifying the thicknesses of the various layers in the diode 106 is another way to decrease resistance in the diode 106.
  • the lateral conduction layer 113 also alleviates the resistance through the diode
  • the lateral conduction layer 113 helps the cu ⁇ ent move to the metal more efficiently.
  • the lateral conduction layer is made of highly doped n + -GaAs.
  • the shunt layer 107 can also be made to partially or completely su ⁇ ound the contact 110, further lowering the series resistance.
  • the lateral conduction layer 113 and the metalization 107 are the two most important means to lessen the amount of voltage needed to "turn on" the diode and bypass
  • the cu ⁇ ent device provides for a low bypass diode turn on, as well as a low series resistance bypass diode. Completion of the bypass diode circuit requires a soldered or welded interconnect made between contacts 109 and 110. This can be done as part of the usual interconnect weld.
  • the fifth step in the manufacturing process is to apply the anti-reflective coating and include etches where external contacts will be attached.
  • the process by which the diode is manufactured is integral to the manufacture of the cell, and does not require additional manufacturing steps or additional layers to be grown on the cell.
  • FIG. 6 is a block diagram 600 illustrating a schematic sectional view showing a multijunction solar cell structure 640 having a bypass diode 620 in accordance with one embodiment of the present invention.
  • Diagram 600 includes a substrate 602, a multijunction solar cell structure 640, a bypass diode 620, a well 650, and a shunt 630.
  • the substrate 602 is a germanium substrate.
  • the multijunction solar cell structure 640 further includes a top, middle, and bottom subcells. It should be noted that terms solar cells, cells, and subcells will be used interchangeably herein.
  • the multijunction solar cell structure is divided into two portions 642-644, wherein portion 642 includes solar cell(s) for converting solar power to electrical power and portion 644 contains a bypass diode 620.
  • the multijunction solar cell structure 640 is a multijunction solar cell structure wherein a bottom solar cell 604 is deposited over the substrate and a middle solar cell 606 is deposited over the bottom solar cell 604.
  • the top solar cell 608 of the multijunction solar cell structure is deposited over the middle solar cell 606.
  • Each solar cell within the multijunction solar cell structure is designed to convert the solar energy within a range of wavelength ⁇ of the solar spectrum.
  • the top solar cell 608 of the multijunction solar cell structure is designed to convert the high frequency portion of the solar spectrum into electrical energy.
  • the high frequency portion may include ultraviolet, X-rays, and/or Gamma rays of the solar spectrum.
  • the high frequency portion covers ⁇ in a range of approximately 700 nm to 100 nm.
  • the middle solar cell 606 is responsible for converting the solar energy in a range of ultraviolet, visible light, and/or portions of infrared of the solar spectrum, which may be approximately between 90 nm to 1000 nm.
  • the bottom solar cell 604 is responsible for converting the solar energy in a range of infrared, microwaves, and/or radio waves, which may be approximately between 700 nm and/or greater.
  • the solar spectrum could be divided into more than three regions and each region has an associated solar cell for capturing photons within the respected region. It should be further noted that the underlying concept of the present invention applies to multijunction solar cell structure 640 containing more or less than three subcells.
  • Diagram 600 further includes a lateral conduction layer 610 and a stop etch layer 612.
  • the lateral conduction layer 610 is heavily doped so that it has the property of high electrical conductivity.
  • the stop etch layer 612 in one aspect, is needed to create a shunt contact pad 652 during the etching process.
  • the bypass diode 620 includes an n-type layer 626, i-type layer
  • n-type layer 626 could be an n-doped gallium arsenic ("GaAs") layer and a p-type layer 622 could be a p-doped GaAs layer.
  • GaAs gallium arsenic
  • a bypass diode with p-on-n polarity is formed when a p-type compound layer is deposited over an n-type compound layer.
  • a bypass diode with n-on-p polarity may be formed when an n-type compound layer is deposited over a p-type compound layer.
  • the i-type layer 624 is also refe ⁇ ed to as an intrinsic layer, lightly doped layer, i-layer and/or non-doping layer. It should be noted that terms i-type layer, intrinsic layer, lightly doped layer, i-layer and undoped layer are interchangeable herein.
  • a function of i-layer 624 is to reduce defect breakdown such as microplasma breakdown. In other words, i-layer 624 reduces leakage cu ⁇ ent when the bypass diode 620 is in reverse bias mode. As discussed above, the bypass diode 620 preserves the integrity of the solar cell by preventing the solar cell from entering the reverse bias mode.
  • the bypass diode 620 is epitaxially formed over the multijunction solar cell structure 640 so that the bypass diode 620 becomes an integral part of the solar cell structure.
  • the bypass diode 620 is part of the monolithic solar cell structure.
  • an i-type layer 624 is deposited over the n-type layer 626.
  • a bypass diode is completed after a p-type layer 622 is deposited over the i-type layer 624.
  • Well 650 in one embodiment, is created by an etch process, such as a mesa etch. This generates a physical space or gap between the solar cell and the bypass diode 620. In other words, well 650 provides an electrical separation between the active portion of the solar cell and the bypass diode 620. Well 650 also provides a path allowing a shunt 630 to access the substrate. In one embodiment, once shunt 630 is deposited, well 650 may be filled with non-conductive materials, such as anti-reflective materials. It should be noted that the width of the gap or space created by the well 650 between the active portion of the solar cell and bypass diode depends on the semiconductor technology.
  • Shunt 630 is deposited via well 650 wherein one side of the shunt 630 is in contact with the substrate and another side of the shunt 630 is in contact with the lateral conduction layer 610. In one embodiment, one side of the shunt 630 is also in contact with a portion of the multijunction solar cell structure 640, which contains the bypass diode 620. In other words, the shunt 630, in this embodiment, shorts a portion of the multijunction solar cell structure that is underneath the bypass diode 620. In this embodiment, the shunt 630 is made of metal to enable it to pass electric cu ⁇ ent from the substrate to the bypass diode 620 with minimal cu ⁇ ent loss. An advantage of using shunt 630 is that it reduces the need for external welding jumpers or shorts, which affect the reliability of the solar cell.
  • FIG. 7 is a logic diagram 700 illustrating a triple junction solar cell structure and a bypass diode 620 in accordance with one embodiment of the present invention.
  • the logic diagram 700 includes a top cell 608, a middle cell 606, a bottom cell 604, a bypass diode 620, a resistance block 702, and four paths 710-716.
  • the resistance block 702 includes resistance from the shorted portion of the multijunction solar cell structure that is situated underneath of the bypass diode 620 and the resistance from the shunt 630.
  • the solar cells 604-608 are in forward biased.
  • solar cells converts solar energy to electrical energy and pass electric cu ⁇ ent between the neighboring solar cells connected in series.
  • sunlight, solar light, light, radiation, and/or photons may be used interchangeable herein.
  • solar cells are organized in a series. While solar cells 604-608 are in forward biased, bypass diode 620 is reverse biased because bypass diode 620 has an opposite polarity from solar cells. Thus, when bypass diode 620 is in reverse bias mode, no electric cu ⁇ ent passes through the bypass diode 620.
  • solar cells 604-608 pass total electrical cu ⁇ ent, which includes the current converted by solar cells 604-608 and the cu ⁇ ent arriving from neighboring solar cells through path 710, to path 716 via path 712.
  • Path 716 may be connected to another solar cell and/or other electrical devices.
  • bypass diode 620 becomes forward biased. In this situation, bypass diode 620 becomes active and passes the cu ⁇ ent from neighboring solar cells via path 710 to path 716 through path 714. In other words, when the solar cells 604-608 are in reverse bias mode, the bypass diode 620 becomes forward biased and uses path 714 to pass the cu ⁇ ent from path 710 to path 716.
  • FIG. 8 is a block diagram 800 illustrating a detailed schematic sectional view showing a triple junction solar cell structure 640 having a bypass diode 620 in accordance with one embodiment of the present invention.
  • the block diagram 800 includes a substrate 602, a triple junction solar cell structure 640, a bypass diode 620, a well 650, and a shunt 630.
  • the triple junction solar cell structure 640 further includes a bottom, middle, and top subcells 604-608.
  • the block diagram 800 also includes contact pads 802-806, wherein contact pad 806 is deposited over a lateral conduction layer 610 and contact pad 804 is deposited over the bypass diode 620.
  • the substrate is a p-type germanium (“Ge”) substrate 602, which is formed over a metal contact pad 802.
  • the bottom cell 604 contains a p-type Ge base layer 810, a n-type Ge emitter layer 812, and a n-type GaAs nucleation layer 814.
  • the base layer 810 is deposited over the substrate 602.
  • the nucleation layer 814 is deposited over the base layer 810, which in one embodiment can be formed through diffusion from an emitter layer 812.
  • a p-type and n- type tunneling junction layers 816 which are also known form a structure sometimes refe ⁇ ed to as tunneling diode, are deposited.
  • the middle cell 606 further includes a back surface field (“BSF") layer 820, a p- type GaAs base layer 822, an n-type GaAs emitter layer 824, and an n-type gallium indium phosphide (“GaInP ”) window layer 826.
  • the base layer 822 is deposited over the BSF layer 820 once the BSF layer 820 is deposited over the tunneling junction layers 816.
  • the window layer 826 is subsequently deposited on the emitter layer 824 after the emitter layer 824 is deposited on the base layer 822.
  • the BSF layer 820 is used to reduce the recombination loss in the middle cell 606.
  • the BSF layer 820 drives minority carriers from a highly doped region near the back surface to minimize the effect of recombination loss. In other words, a BSF layer 820 reduces recombination loss at the backside of the solar cell and thereby reduces the recombination at the emitter region.
  • the window layer 826 used in the middle cell 606 also operates to reduce the recombination loss.
  • the window layer 826 also improves the passivation of the cell surface of the underlying junctions. It should be apparent to one skilled in the art that additional layer(s) may be added or deleted in block diagram 800 without departing from the scope of the present invention.
  • p-type and n-type tunneling junction layers 830 are deposited over the middle cell 606.
  • the top cell 608, includes a p-type indium gallium aluminum ⁇ hosphide 2 ("InGaAlP 2 ") BSF layer 840, a p-type GaInP 2 base layer 842, an n- type GaInP2 emitter layer 844, and an n-type aluminum indium phosphide 2 ("AlIrdY') window layer 846.
  • the base layer 842 is deposited on the BSF layer 840 once the BSF layer 840 is deposited over the tunneling junction layers 830.
  • the window layer 846 is subsequently deposited on the emitter layer 844 after the emitter layer 844 is deposited on the base layer 842.
  • an n-type GaAs cap layer 850 is employed for enhancing better contact with metal materials.
  • the cap layer 850 is deposited over the top cell 608.
  • the lateral conduction layer 610 formed of n-type GaAs, is deposited over the cap layer 850.
  • An n-type GaInP 2 stop etch layer is deposited over the lateral conduction layer 610. After the stop etch layer is deposited, the bypass diode is epitaxially deposited.
  • the bypass diode 620 includes an n-type GaAs layer 860, an i-type GaAs layer 862 layer, and a p-type GaAs layer 864.
  • the n-type layer 860 is deposited over the stop etch layer 612.
  • the i-type layer 862 is deposited over the n-type layer 860.
  • the p-type layer 864 is deposited over the i-type layer 862.
  • a contact pad 804 is deposited over the bypass diode 620. Once the contact pad 804 is formed, a p- i-n bypass diode with p-on-n polarity is formed over the solar cell.
  • an n-i-p bypass with n-on-p polarity bypass diode can be also formed over a solar cell structure using similar process described above. It should be apparent to one skilled in the art that the additional layer(s) may be added or deleted in the bypass diode 620 without departing from the scope of the present invention.
  • a metal shunt 630 is deposited via well 650.
  • One side of the shunt 630 is connected to the substrate 602 and another side of the shunt 630 is connected to the lateral conduction layer 610 and a portion of the triple junction cell 644.
  • An anti- reflection coating may be deposited over certain parts of the solar cell to enhance solar cell performance.
  • the multijunction solar cell structure could be formed by any combination of group III to V elements listed in the periodic table, wherein the group III includes boron (B), Aluminum (Al), Gallium (Ga), Indium (In), and thallium (TI).
  • the group IV includes carbon (C), Silicon (Si), Ge, and Tin (Sn).
  • the group V includes nitrogen (N), phosphorus (P), Arsenic (As), antimony (Sb), and bismuth (Bi).
  • FIG. 9A-9E are block diagrams illustrating a process of manufacturing a multijunction solar cell structure 640 with a bypass diode 620 and a shunt 630 in accordance with one embodiment of the present invention.
  • FIG. 9A illustrates a triple junction solar cell structure 900 with an integral bypass diode 602 epitaxially formed on the triple junction solar cell structure 900.
  • the triple junction solar cell 900 includes a bottom, middle, and top cell 604-608.
  • FIG. 9B illustrates that a portion 922 of bypass diode 602 has been etched away.
  • FIG. 9C illustrates that a well 932 is created through an etching process, such as a mesa etch method.
  • FIG. 9D illustrates that a second portion 942 of the bypass diode 620 is etched away.
  • the stop etch layer 612 is, in one embodiment, used to control the etching process to remove the portion 942 of the bypass diode 620 to create a shunt contact pad 652.
  • FIG. 9E illustrates the next step of formation of the shunt 952. It should be apparent to one skilled in the art that additional layers and steps may be added or deleted without departing from the scope of the present invention.
  • FIG. 10 is a flow chart 1000 illustrating a method of manufacturing a multijunction solar cell structure with a bypass diode in accordance with one embodiment of the present invention.
  • the process deposits a germanium substrate.
  • the germanium substrate is deposited over a contact layer. Once the substrate is formed, the process moves to block 1012.
  • the process deposits a solar cell.
  • the solar cell is a triple junction solar cell, which includes a bottom, middle, and top subcells.
  • the bottom subcell may be a germanium solar subcell and the middle subcell may be a GaAs solar subcell.
  • the top subcell may be a GaInP2 solar subcell. It should be noted that it does not depart from the scope of the present invention if the homojunction subcells are replaced with heterojunction subcells. After the solar cell is formed, the process proceeds to block 1014.
  • the process deposits a lateral conduction layer over the solar cell.
  • the lateral conduction layer is a n-doped GaAs layer, which is used as the shunt contact pad.
  • the process proceeds to block 1016.
  • the process deposits a bypass diode over the lateral conduction layer.
  • an n-type GaAs layer is deposited over the stop etch layer.
  • a p-type GaAs layer is deposited over the i-type layer.
  • the concentration of n dopant in the n-type GaAs layer is between 10 17 to 101 R .
  • 17 ⁇ o layer is between 10 to 10 .
  • concentration of dopant for i-tape GaAs layer is less than 10 16 .
  • a well or gap or space is created to provide electrical separation between the bypass diode and the solar cell. Well also allows the shunt to access the substrate. After the creation of well, the process proceeds to block 1020.
  • a shunt is deposited along a portion of the multijunction solar cell structure wherein one side of the shunt is connected to the substrate and another side of the shunt is connected to the shunt contact pad.

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Abstract

L'invention concerne une cellule solaire présentant une structure de cellule solaire à multiples raccordements avec une diode en parallèle. La diode en parallèle offre une protection de polarisation inverse pour la structure de cellule solaire à multiples raccordements. Dans un mode de réalisation, la structure de cellule solaire à multiples raccordements comprend un substrat, une cellule inférieure, une cellule intermédiaire, une cellule supérieure, une diode en parallèle, une couche conductrice latérale, et un circuit parallèle. La couche conductrice latérale est déposée sur la cellule supérieure. La diode en parallèle est déposée sur la couche conductrice latérale. Un côté du circuit parallèle est connecté au substrat et un autre côté du circuit parallèle est connecté à la couche conductrice latérale. Dans un autre mode de réalisation, la diode parallèle contient une couche i destinée à augmenter l'efficacité de la diode.
PCT/US2002/034416 2001-10-24 2002-10-24 Appareil et procede d'integration d'une diode en parallele dans des cellules solaires WO2003054926A2 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
AU2002365270A AU2002365270A1 (en) 2001-10-24 2002-10-24 An apparatus and method for integral bypass diode in solar cells
JP2003555555A JP4119844B2 (ja) 2001-10-24 2002-10-24 太陽電池の一体型バイパスダイオードのための装置及び方法
EP02805514A EP1440480B1 (fr) 2001-10-24 2002-10-24 Appareil et procede d'integration d'une diode en parallele dans des cellules solaires
DE60229279T DE60229279D1 (de) 2001-10-24 2002-10-24 Integrierte umleitungsdiode in solarzellen und herstellungsverfahren
DE10297371T DE10297371T5 (de) 2001-10-24 2002-10-24 Vorrichtung und Verfahren für eine integrale Bypassdiode in Solarzelle

Applications Claiming Priority (3)

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US09/999,598 2001-10-24
US09/999,598 US6680432B2 (en) 2001-10-24 2001-10-24 Apparatus and method for optimizing the efficiency of a bypass diode in multijunction solar cells
US99959802A 2002-10-24 2002-10-24

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WO2006025260A1 (fr) * 2004-08-31 2006-03-09 Kyoto University Cellule solaire hybride organique-inorganique empilee a haut rendement
JP2007537584A (ja) * 2004-05-12 2007-12-20 アズール・スペース・ソーラー・パワー・ゲーエムベーハー 組み込まれた保護ダイオードを有するソーラーセル
US9716196B2 (en) 2011-02-09 2017-07-25 Alta Devices, Inc. Self-bypass diode function for gallium arsenide photovoltaic devices
CN112038419A (zh) * 2020-08-03 2020-12-04 上海空间电源研究所 一种兼具激光供能与太阳发电的光伏电池制作方法
US11121272B2 (en) 2011-02-09 2021-09-14 Utica Leaseco, Llc Self-bypass diode function for gallium arsenide photovoltaic devices

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US6103970A (en) * 1998-08-20 2000-08-15 Tecstar Power Systems, Inc. Solar cell having a front-mounted bypass diode
WO2001006565A1 (fr) * 1999-07-14 2001-01-25 Hughes Electronics Corporation Ensemble monolithique diode en parallele et pile solaire
US6278054B1 (en) * 1998-05-28 2001-08-21 Tecstar Power Systems, Inc. Solar cell having an integral monolithically grown bypass diode

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Publication number Priority date Publication date Assignee Title
US6278054B1 (en) * 1998-05-28 2001-08-21 Tecstar Power Systems, Inc. Solar cell having an integral monolithically grown bypass diode
EP0971417A2 (fr) * 1998-06-11 2000-01-12 Canon Kabushiki Kaisha Elément photovoltaique et son procédé de fabrication
US6103970A (en) * 1998-08-20 2000-08-15 Tecstar Power Systems, Inc. Solar cell having a front-mounted bypass diode
WO2001006565A1 (fr) * 1999-07-14 2001-01-25 Hughes Electronics Corporation Ensemble monolithique diode en parallele et pile solaire

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007537584A (ja) * 2004-05-12 2007-12-20 アズール・スペース・ソーラー・パワー・ゲーエムベーハー 組み込まれた保護ダイオードを有するソーラーセル
WO2006025260A1 (fr) * 2004-08-31 2006-03-09 Kyoto University Cellule solaire hybride organique-inorganique empilee a haut rendement
JPWO2006025260A1 (ja) * 2004-08-31 2008-05-08 国立大学法人京都大学 積層型有機無機複合高効率太陽電池
US9716196B2 (en) 2011-02-09 2017-07-25 Alta Devices, Inc. Self-bypass diode function for gallium arsenide photovoltaic devices
US11121272B2 (en) 2011-02-09 2021-09-14 Utica Leaseco, Llc Self-bypass diode function for gallium arsenide photovoltaic devices
US11211506B2 (en) 2011-02-09 2021-12-28 Utica Leaseco, Llc Self-bypass diode function for gallium arsenide photovoltaic devices
US11695088B2 (en) 2011-02-09 2023-07-04 Utica Leaseco, Llc Self-bypass diode function for gallium arsenide photovoltaic devices
CN112038419A (zh) * 2020-08-03 2020-12-04 上海空间电源研究所 一种兼具激光供能与太阳发电的光伏电池制作方法

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