TW201329009A - Controlling alkali in CIGS thin films via glass and application of voltage - Google Patents

Abstract

A method of moving alkali metal ions in a glass substrate to form a glass substrate having an intrinsic alkali metal barrier layer or an enhanced alkali metal layer by applying voltage to at least one of the surfaces of the substrate such that at least a portion of the alkali metal ions, alkaline earth metal ions, or the combination thereof in the at least one surface move into the thickness of the glass substrate.

Description

Controlling alkali metal in cadmium indium gallium selenide film by glass and voltage application [Cross-reference to related applications]

The present patent application is based on the priority of the U.S. Provisional Patent Application Serial No. 61/565,109, filed on November 30, 2011, the content of which is hereby The citations are all incorporated herein.

The present disclosure relates generally to a glass substrate having a diffusion barrier layer or a reinforced alkali metal layer, and more particularly to a glass substrate having an alkali metal diffusion barrier layer or a reinforced alkali metal layer, the glass substrate being usable For optoelectronic applications, such as thin film photovoltaic (PV) devices and methods of making the same.

One problem faced by the photovoltaic industry today in the development of thin film solar panel technology is the control of alkali metal transport from the substrate into the deposited semiconductor film. The two photovoltaic thin film technologies currently in development are cadmium telluride (CdTe) and cadmium indium gallium selenide (CIGS). In the case of cadmium telluride, a thin film stack is deposited on a glass upper plate through which sunlight must pass. It has been demonstrated that the incorporation of alkali metal ions into a transparent conductive oxide (TCO) and/or cadmium telluride film reduces the efficiency with which the device converts sunlight into electricity. At present, the barrier layer most commonly used for cadmium telluride film stacking is sputter deposited cerium oxide (SiO ₂ ) or aluminum oxide (Al ₂ O ₃ ). These barrier layers prevent alkali metal ions from escaping from the glass plate but are not completely prevented.

In the case of cadmium indium gallium selenide, the film was deposited on a glass substrate that was not directly exposed to sunlight. The incorporation of sodium, potassium and other possible alkali metals into the cadmium indium gallium selenide semiconductor film during deposition can alter the microstructure of the cadmium indium gallium selenide semiconductor film, which ultimately enhances the device's ability to convert sunlight into electricity. effectiveness. It is also shown that the presence of an optimum concentration of alkali metal ions in the cadmium indium gallium selenide film can produce maximum cell efficiency. This optimum concentration can vary depending on the particular process used to prepare the cadmium indium gallium selenide film (e.g., co-evaporation, rapid thermal processing, batch selenization) and the manufacturer's specific optimization of the custom process.

The most commonly used substrate for cadmium telluride and cadmium indium gallium selenide technology is sodium carbonate-lime-stron oxide (SLG) float glass. The reason why this glass material is mainly used is that it is immediately available, low in cost, and contains a high concentration of sodium. This last trait is ideal for some cadmium indium gallium selenide processes (such as rapid thermal processing and co-evaporation) because high concentrations of sodium can cause rapid sodium transport during film deposition and can produce high cell efficiencies. Typically the cadmium indium gallium selenide film of about ³ per cm A dopant level of 1 x 10 ¹⁹ sodium atoms results in higher cell efficiencies. The general thickness of cadmium indium gallium selenide film is 2.5 microns (m or um). Therefore, for a thinner cadmium indium gallium selenide film, the sodium concentration required per square centimeter of photovoltaic cells can be estimated to be 95 ng/cm ² or less. The sodium content of 1 gram of salt (NaCl) is approximately the same as that of a 1 square inch, 3 mm thick, sodium carbonate-lime-yttria glass (SLG) plate typically made using a floating process, which is sufficient to be about 41,000 m ² The cadmium indium gallium selenide battery is doped to a level of 1 x 10 ¹⁹ atoms/cm ³ . This simply illustrates the presence of sufficient sodium in the SLG glass.

It is interesting to note that the first 4 nm surface may contain all of the sodium required to incorporate a cadmium indium gallium selenide film. Although there is sufficient sodium, there is a need to control the total amount and the rate at which the glass surface is released. The sodium transfer rate appears too fast for some cadmium indium gallium selenide processes (eg, batch selenization) and, more importantly, uncontrollable. Since SLG glass ages under ambient conditions of temperature and humidity, the surface chemistry of the SLG glass changes, resulting in a spatially non-uniform sodium release during the deposition of the cadmium indium gallium selenide film.

As a result, some solutions are being investigated that integrate an external dopant layer that delivers all of the desired sodium into the cadmium indium gallium selenide film in a controlled manner. In these product designs, it is desirable to completely prevent alkali metal from escaping from the underlying glass substrate. In order to achieve this, a barrier layer that prevents alkali metal from diffusing from the glass substrate into the external alkali metal dopant layer and the cadmium indium gallium selenide film is being developed. The barrier layer must also prevent or minimize the diffusion of alkali metal ions from the outer dopant layer back to itself such that all of the alkali metal ions are available for diffusion into the cadmium indium gallium selenide film. At present, the most common barrier layer for cadmium indium gallium selenide film stack is sputter deposited yttrium oxide or aluminum oxide. These barrier layers can inhibit alkali metal ions from running out of the glass substrate, but not completely prevent. In addition, these barrier layers have been found to be ineffective in preventing the alkali metal from the external dopant layer from diffusing back to itself.

An additional requirement for the glass substrate or the upper plate is to have a similar coefficient of thermal expansion (CTE) as the cadmium indium gallium selenide or cadmium telluride film to maximize adhesion and prevent film delamination. In the design of most cadmium telluride and cadmium indium gallium selenide photovoltaic modules, two sheets of glass are used as the substrate and the upper plate material. It is desirable that at least one of the glass sheets is SLG float glass because of its low cost. In such a product architecture, the coefficient of thermal expansion (CTE) of the two glass sheets should be similar to prevent mechanical deformation during the lamination process.

A further desirable glass property is stability at elevated temperatures. The performance of cadmium telluride and cadmium indium gallium selenide batteries can be enhanced at higher processing temperatures. The nature that best describes this temperature resistance in glass is the strain point and the annealing point. It is very difficult to design a single glass composition that can effectively meet all of the thermal expansion, temperature resistance, and variable alkali metal transfer requirements. One way to meet these conflicting requirements is to design a glass composition that meets the thermal expansion coefficient and thermal stability requirements and then design its surface chemistry to control the transport of the alkali metal.

Additional features and advantages will be set forth in the <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; The present invention described in the claims is intended to understand such features and advantages.

Due to the inhibition of sodium diffusion or the concentration of sodium is present in the glass The concentration limit of the typical photo-cadmium indium gallium selenide treatment (when no voltage is applied) is limited to the cadmium indium gallium selenide layer and the molybdenum (Mo) layer. An improvement over the prior art photovoltaic cells is that the diffusion rate of sodium is accelerated and the sodium content in the battery is increased beyond the level of the glass. The applied voltage increases the rate of diffusion of the sodium species by applying a voltage. Second, a voltage is applied to produce abundant sodium at the voltage application, and thus the sodium concentration in the molybdenum and cadmium indium gallium selenide layers can be increased.

Applying a negative voltage to the glass surface will cause the moving, positively charged alkali and alkaline earth metal ions to migrate/diffuse toward the glass surface and create a surface layer rich in these species. Conversely, applying a positive voltage to the glass surface will cause the moving, positively charged alkali and alkaline earth metal ions to migrate/diffuse away from the glass surface and create a surface layer that is depleted of these species. The applied voltage can be used to produce an alkali metal-rich surface layer or an alkali metal-depleted surface layer. In addition, the technique can be modified to control the richness or depletion of the alkali metal (e.g., partially rich or partially depleted) as needed to control the amount and rate of alkali metal released from the glass surface into the subsequently deposited film. The thickness of the rich or depleted surface layer can range from a few nanometers to about 10 microns, such as from 3 nanometers to 10 microns, such as from 10 nanometers to 1 micrometer.

One embodiment is a method of moving an alkali metal ion in a glass substrate to form a glass substrate having an intrinsic alkali metal barrier layer, the method comprising the steps of: providing a glass substrate comprising an alkali metal ion, an alkaline earth metal ion, or a combination of the foregoing, and the glass substrate has at least two opposing surfaces and a thickness interposed between the surfaces; Applying a voltage to the two surfaces of the substrate such that at least a portion of the alkali metal ions, alkaline earth metal ions, or a combination of the above materials in at least one surface moves deeper into the thickness to form the glass having the intrinsic alkali metal barrier layer Substrate.

Another embodiment is a method of moving an alkali metal ion in a glass substrate to form a glass substrate having a reinforced alkali metal layer, the method comprising the steps of: providing a glass substrate comprising an alkali metal ion, an alkaline earth metal ion, or the like a combination of materials, and the glass substrate has at least two opposing surfaces and a thickness interposed between the surfaces; and applying a voltage to the two surfaces of the substrate such that at least a portion of the alkali metal ions, alkaline earth metals in the vicinity of at least one surface The ions or a combination of the above species move away from the negative voltage and go to a positive voltage on the opposite surface to form the glass substrate with the reinforcing alkali metal layer.

Another embodiment is an article comprising a glass substrate having a first region of depleted alkali metal ions, alkaline earth metal ions or a combination thereof; and an alkali metal ion, an alkaline earth metal ion having a substantially uniform concentration or A second region of the combination of the foregoing materials, the second region being in physical contact with the first region, wherein the glass substrate does not have a third region having an increased concentration of alkali metal ions, alkaline earth metal ions, or a combination thereof.

It is to be understood that the foregoing general description and the following embodiments are merely illustrative of the embodiments of the invention

The accompanying drawings are included to provide a further understanding of the invention and The figures are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments of the invention, and are in the

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The invention may be understood from the following embodiments, either alone or in conjunction with the drawings.

FIG sodium diffusion final result of the first glass substrate 1 graph illustrating the glass substrate into the salt bath of potassium.

Figure 2 is a schematic illustration of a method in accordance with some embodiments.

Figure 3 is a graph showing the total amount of predicted sodium (in ng) delivered from the glass as the time and temperature are plotted during the ion exchange process.

4A , 4B, and 4C are schematic diagrams of illustrative method steps in accordance with some embodiments.

Figure 5 is a plot of the current of the SLG-type glass as a function of time.

Figure 6 is a graph of sodium distribution taken on the non-tin side of SLG glass by secondary ion mass spectrometry (SIMS).

7 photo shows measured by SIMS example cadmium indium gallium selenide and sodium profile molybdenum film 1.

Figure 8 is a graph showing the current performance of an electric field of 50 volts applied to Examples 1 and 2.

Figure 9 is a graph of the sodium distribution of Example 2 as measured by SIMS.

Figure 10 is a graph showing the potassium distribution of cadmium indium gallium selenide and molybdenum film of Example 2 by SIMS.

Figure 11 is a graph of the sodium distribution of Example 3 as measured by SIMS.

Figure 12 is a graph of the sodium distribution of Example 4 as measured by SIMS.

Figure 13 is a graph of the sodium distribution of Example 5 as measured by SIMS.

Figure 14 illustrates features of an optoelectronic device in accordance with one embodiment.

Figure 15 illustrates features of a glass substrate in accordance with some embodiments.

Various embodiments of the invention will now be described in detail.

Depending on the structure of the photovoltaic cell, the term "substrate" as used herein may be used to describe a substrate or an upper plate. For example, if assembled to a photovoltaic cell on the light incident side of the photovoltaic cell, the substrate is an upper plate. The upper plate protects the photovoltaic material from impact and environmental degradation while allowing the proper wavelength of solar spectrum transmission. In addition, a plurality of photovoltaic cells can be configured as a photovoltaic module. The optoelectronic device can describe either or both of the battery and the module.

The term "adjacent" as used herein may be defined as being in the vicinity. Adjacent structures may or may not be in physical contact with each other. Other layers and/or structures may be provided in the middle of adjacent structures.

One embodiment is a method of moving an alkali metal ion in a glass substrate to form a glass substrate having an intrinsic alkali metal barrier layer, the method comprising the steps of: providing a glass substrate comprising an alkali metal ion, an alkaline earth metal ion, or a combination of the foregoing, and the glass substrate has at least two opposing surfaces and a thickness interposed between the surfaces; and applying a voltage to the two surfaces of the substrate such that in at least one surface A small portion of the alkali metal ion, alkaline earth metal ion or a combination of the above substances moves deeper into the thickness to form the glass substrate having the intrinsic alkali metal barrier layer.

Another embodiment is a method of moving an alkali metal ion in a glass substrate to form a glass substrate having a reinforced alkali metal layer, the method comprising the steps of: providing a glass substrate comprising an alkali metal ion, an alkaline earth metal ion, or the like a combination of materials, and the glass substrate has at least two opposing surfaces and a thickness interposed between the surfaces; and applying a voltage to the two surfaces of the substrate such that at least a portion of the alkali metal ions, alkaline earth metals in the vicinity of at least one surface The ions or a combination of the above species move away from the negative voltage and go to a positive voltage on the opposite surface to form the glass substrate with the reinforcing alkali metal layer.

The glass substrate produced according to the disclosed method may have a first region of a depleted alkali metal ion, an alkaline earth metal ion or a combination thereof; and an alkali metal ion, an alkaline earth metal ion or a combination thereof a second region in contact with the first region entity, wherein the glass substrate does not have a third region having an increased concentration of alkali metal ions, alkaline earth metal ions, or a combination thereof.

Another embodiment is an article comprising a glass substrate having a first region of depleted alkali metal ions, alkaline earth metal ions or a combination thereof; and an alkali metal ion or alkaline earth metal having a substantially uniform concentration a second region of ions or a combination of the foregoing, the second region being in physical contact with the first region, wherein the glass substrate does not have an increased concentration A third region of an alkali metal ion, an alkaline earth metal ion, or a combination thereof.

Both positive and negative voltages can be used to control the amount of alkali metal migration that occurs in the glass substrate, and then enter the amount of alkali metal from the glass substrate, for example, a cadmium indium gallium selenide photovoltaic cell. In some embodiments, voltages in the range of +10 kv and -100 kv are applied to a glass substrate with or without additional layers, for example, a voltage in the range of -0.5 volts to -100 kv is applied to Glass substrates with or without additional layers, for example, applying a voltage in the range of -0.5 volts to -10 kV to a glass substrate with or without additional layers, for example at a level ranging from -0.5 volts to -1 kv The voltage in is applied to a glass substrate with or without additional layers, or for example a voltage in the range of -5 volts to -100 kv is applied to a glass substrate with or without additional layers, for example at a level from -5 A voltage in the range of volts to -10 kv is applied to a glass substrate with or without additional layers, for example a voltage in the range of -5 volts to -1 kv is applied to a glass substrate with or without additional layers.

In some embodiments, a voltage of 1 kV or less is applied to a glass substrate with or without additional layers, such as applying a voltage of 750 volts or less to a glass substrate with or without additional layers, such as Applying a voltage of 700 volts or less to a glass substrate with or without additional layers, for example applying a voltage of 650 volts or less to a glass substrate with or without additional layers, for example a level of 600 volts applied. Or lower voltage on a glass substrate with or without additional layers, for example applying a voltage of 550 volts or less to a glass substrate with or without additional layers, for example applying a voltage of 500 volts or less. Glass substrate with or without additional layers, for example, applying a voltage of 450 volts or less to the glass with or without additional layers Substrate, for example, applying a voltage of 400 volts or less to a glass substrate with or without additional layers, for example applying a voltage of 350 volts or less to a glass substrate with or without additional layers, such as applying a level A voltage of 300 volts or less is applied to a glass substrate with or without additional layers, for example, a voltage of 250 volts or less is applied to a glass substrate with or without additional layers.

In some embodiments, a voltage of -5 volts to 1 kV is applied to the glass substrate with or without additional layers, such as applying a voltage from -5 volts to 750 volts to the glass with or without additional layers. Substrate, for example, applying a voltage from -5 volts to 700 volts to a glass substrate with or without additional layers, such as applying a voltage from -5 volts to 650 volts to a glass substrate with or without additional layers, For example, applying a voltage from -5 volts to 600 volts to a glass substrate with or without additional layers, for example applying a voltage from -5 volts to 550 volts to a glass substrate with or without additional layers, such as application The level is from -5 volts to 500 volts on a glass substrate with or without additional layers, for example, applying a voltage from -5 volts to 450 volts to a glass substrate with or without additional layers, such as applying a level For a voltage from -5 volts to 400 volts on a glass substrate with or without additional layers, for example, applying a voltage from -5 volts to 350 volts to a glass substrate with or without additional layers, such as Voltage level from -5 volts to 300 volts to the glass substrate with or without additional layers, such as the level applied to the glass substrate with or without an additional layer having a voltage from -5 volts to 250 volts.

In some embodiments, a voltage of from 1 volt to 1000 volts is applied, such as a voltage from 1 volt to 950 volts, such as a voltage from 1 volt to 900 volts, such as an applied level of 1 volt A voltage of up to 900 volts, for example a voltage of 1 volt to 850 volts, for example a voltage of 1 volt to 800 volts, for example a voltage of 1 volt to 750 volts, for example a applied level A voltage of 1 volt to 700 volts, for example a voltage of 1 volt to 650 volts is applied, for example a voltage of 1 volt to 600 volts is applied, for example a voltage of 1 volt to 550 volts, such as a applied level. A voltage of from 1 volt to 500 volts is applied, for example, a voltage of 2 volts to 500 volts is applied, for example, a voltage of 3 volts to 500 volts is applied, for example, a voltage of 4 volts to 500 volts is applied, for example A voltage of 5 volts to 500 volts is applied.

Various voltages can be applied for different lengths of time. A negative voltage will help to transport the alkali metal, while a positive voltage can turn off or slow the rate or amount of alkali metal migration. The time during which the voltage is applied can vary between 1 nanosecond and several days. The total current applied in a certain temperature range can be used to determine the amount of ion migration of the glass.

The voltage can be applied in several different ways, including: applying a voltage to the molybdenum film during the deposition of the cadmium indium gallium selenide; after the deposition of the cadmium indium gallium selenide but during the high temperature heat treatment, the cadmium indium gallium selenide or molybdenum Applying a voltage to the film; applying a voltage to the molybdenum film and then heating the glass/molybdenum film to a temperature exceeding 50 ° C; applying a voltage to the multilayer film at a temperature between 20 ° C and 400 ° C to change the alkali metal content in the battery; A voltage is applied after application of the cadmium indium gallium selenide but prior to deposition of the final cover layer (eg, CdS and/or ZnO); or application of a voltage and thermal low temperature treatment after all of the multilayer coating has been applied.

The method can include applying a voltage to the plain glass that is heated prior to applying the molybdenum film to produce an alkali metal-rich surface. As an example, Electrodes coated with gold, silver, graphite, platinum, palladium, copper, aluminum or other metal alloys known to those of ordinary skill in the art may be pressed onto the glass surface upon heating.

Conventional alkali metal-tellurate glasses (such as the glasses used in the present disclosure) are ionic conductors. At room temperature the glass is an insulator, however, at elevated temperatures, the monovalent cations become mobile in the glass. When the glass is at an elevated temperature (T > 75 ° C), contains a high concentration of mobile ions and / or is in the presence of an electric field, the alkali metal ions will move toward one surface of the glass and away from the other surface through the glass The internet. For example, glass with a large amount of sodium (such as commercially available soda lime citrate) will naturally form a sodium-rich layer on the glass surface at temperatures > 50 ° C but < 100 ° C. The driving force behind the presence of an enhanced alkali metal migration is superior to the temperature only and allows for the determination of the direction of migration, for example, the alkali metal ions will move toward the negatively biased surface and away from the positively biased surface.

The theory of weak electrolytes indicates that the conductivity of ions is the product of the concentration of mobile ions and the mobility of conductive ions [Equation 1]: σ = n * zeu Equation 1 where σ is the ionic conductivity and n * is the mobile ion per unit volume The number, z is the charge of the moving ion, e is the electron charge, and u is the mobility of the ion. One of the focuses of the present disclosure is to maintain the conductivity of the alkali metal ions, but to reduce n *, the number of mobile ions per unit volume in the glass body. It is still controversial why sodium can improve battery efficiency, but sodium does improve battery efficiency. There may be multiple effects. This disclosure confirms that a wide variety of glasses can be used in the process. As an example, glass with less alkali metal can allow cadmium indium gallium selenide to be fabricated at higher temperatures. This can be improved by producing a better performing crystal structure or by changing the grain size or the sodium content in the grain or grain boundaries.

In order to maintain the conductivity of the ions on the glass surface, we propose to use an electric field to attract the alkali metal in the glass body to the surface, and the cadmium indium gallium selenide layer will be placed on the surface of the glass. The alkali metal ions in the glass are attracted to the cathode, and the rate of movement of the ions can be manipulated via temperature, time, and voltage intensity applied across the glass, thus allowing modification of the alkali metal distribution of the surface. Modifying the alkali metal distribution in the glass allows for a high mobile ion concentration on the surface, maintaining a conductivity similar to that of a high alkali metal content glass, but keeping the alkali metal in the glass body low, thus obtaining a high strain point glass Technical advantage.

FIG sodium diffusion final result of the first glass substrate 1 graph illustrating the glass substrate into the salt bath of potassium. In this example, the sodium-containing glass substrate is placed in a potassium salt bath and heated to 600 ° C for a fixed length of time, such as 40 minutes. The end result is the diffusion of sodium out of the glass substrate - line 12 . The salt bath diffusion data illustrated in Figure 1 is the predicted sodium distribution in the glass using the same heat profile as used for applying the cadmium indium gallium selenide coating on the same glass substrate. However, Figure 1 shows that the actual sodium distribution - line 10 of the glass surface below the cadmium indium gallium selenide film is virtually undetectable compared to what is expected for the surface of the glass ion exchanged in the salt bath. Sodium loss. This demonstrates that standard cadmium indium gallium selenide treatment (ie, those that do not involve the application of voltage or ion exchange species) produces very little sodium migration.

Figure 2 is a schematic illustration of a method in accordance with some embodiments. It is shown that a voltage is being applied to the molybdenum film during the heat treatment to control the amount of sodium entering the cadmium indium gallium selenide film. A voltage V may be applied to at least one surface of the molybdenum film 16 and the glass substrate 14 during the heat treatment. The amount of sodium entering the cadmium indium gallium selenide film can be controlled by applying a voltage to the molybdenum film.

Figure 3 is a graph showing the predicted total amount of sodium (in ng) from the glass to the multilayer (e.g., cadmium indium gallium selenide layer) as the number of time and temperature. Lines 24, 22, 20, and 18 illustrate temperature profiles of 225 ° C, 250 ° C, 350 ° C, and 500 ° C, respectively. This prediction is to extrapolate lower temperature sodium diffusion data at 500 ° C and 600 ° C. It is assumed that the applied voltage can produce a similar diffusion rate as in a salt bath. In fact, applying a larger voltage can actually enhance the diffusion of the deeper layer, and the actual diffusion value may be larger than those illustrated in the figure with respect to the extrapolated value. There is a lot of sodium that can be extracted from the cadmium indium gallium selenide layer, even at temperatures below 400 °C. The figure shows that doping the multilayer at low temperatures does indeed take place over a reasonable length of time. The extrapolated data shown here indicates that 1 x 10 ¹⁹ sodium atoms/cm ³ (~95 ng sodium/cm ² cells, 2.5 um thick cadmium indium gallium) can be achieved at 250 ° C or higher within 1 day. The doping level of the selenide layer). Most of the sodium is expected to be distributed at the grain boundaries.

The alkali metal distribution in the glass can be customized by applying a positive voltage and then applying no voltage or even applying a negative voltage for different lengths of time, as schematically illustrated in Figures 4A , 4B and 4C . Or by applying an alkali metal containing film or an alkali metal containing bath and subsequently applying a voltage with or without heat.

4A , 4B, and 4C are schematic diagrams of illustrative method steps in accordance with some embodiments. The method steps can be used to create a reinforced alkali metal layer on or adjacent the surface of the glass substrate. Figure 4A illustrates that the as-prepared glass has a substantially uniform sodium level-line 21 throughout the surface and body prior to any treatment. 4B illustrates that during the exemplary step 1, the surface 23 of the glass substrate is enriched with an alkali metal, and the body begins to consume alkali metal when the sample is heated in the presence of a voltage. 4C illustrates that during the exemplary step 2, reversing the bias or removing the bias under heating can drive the alkali metal into the surface-line 25 .

In one embodiment, as illustrated in FIG. 14, wherein the optoelectronic device 101 includes a glass substrate 86, a glass substrate 86 has an inherent alkali metal barrier layer produced according to the methods described herein, or an alkali metal reinforcing layer 90. The optoelectronic device may comprise more than one glass substrate, for example as a substrate and/or as an upper plate. In one embodiment, optoelectronic device 101 includes a glass sheet as a substrate and/or upper plate 86 , a conductive material 88 adjacent the substrate, and an active photo-electric medium 92 adjacent the conductive material. In one embodiment, the active photovoltaic medium comprises a cadmium indium gallium selenide layer. In one embodiment, the active photovoltaic medium comprises a cadmium telluride (CdTe) layer. In one embodiment, the optoelectronic device comprises a functional layer comprising copper indium gallium diselenide or cadmium telluride. In one embodiment, the functional layer of the optoelectronic device is copper indium gallium diselide. In one embodiment, the functional layer is a cadmium telluride.

In the cadmium indium gallium selenide, the molybdenum back contact conductive layer may be directly deposited on the glass substrate (adjacent to the barrier layer) and interposed between the glass substrate and the cadmium indium gallium selenide functional layer. This molybdenum film may be layer 88 in Figure 14 .

In one embodiment, the barrier layer is adjacent to a transparent conductive oxide (TCO) layer, wherein the transparent conductive oxide layer is between the functional layer and the barrier layer or with the functional layer and the resistor The barrier is adjacent. The transparent conductive oxide may be present in an optoelectronic device comprising a cadmium telluride functional layer.

In one embodiment, feature 201 of glass substrate 86 is illustrated in Figure 15 . The glass substrate may have a first region 94 of depleted alkali metal ions, alkaline earth metal ions or a combination thereof; and a second region 96 having a substantially uniform concentration of alkali metal ions, alkaline earth metal ions or a combination thereof. The second region 96 is in physical contact with the first region, wherein the glass substrate does not have a third region having an increased concentration of alkali metal ions, alkaline earth metal ions, or a combination thereof. The concentration of the alkali metal ion, the alkaline earth metal ion or a combination of the above in the second region may be the same as found in the bulk glass or the initially formed glass before the voltage is applied.

In another embodiment, the glass substrate may further comprise another region 98, region 98 having an increased concentration of alkali metal ions, alkaline earth metal ion or a combination of the foregoing, wherein the concentration increases physical contact with the second layer region, And the concentration increasing layer may have the same concentration as found in the bulk glass or the initially formed glass before the voltage is applied. In this embodiment, the first area may not be present.

In one embodiment, the glass sheet is optically transparent. In one embodiment, the glass sheet as the substrate and/or the upper plate is optically transparent.

According to some embodiments, the glass substrate has a thickness of 4.0 mm or less, for example the glass substrate has a thickness of 3.5 mm or less, for example the glass substrate has a thickness of 3.2 mm or less, for example the glass substrate has 3.0 mm Or a smaller thickness, for example, the glass substrate has a thickness of 2.5 mm or less, for example, the glass substrate has a thickness of 2.0 mm or less, for example, the glass substrate has a thickness of 1.9 mm or less, for example, the glass substrate has a thickness of 1.8 mm or less, for example, the glass substrate has a thickness of 1.5 mm or less, for example, the glass substrate has a thickness of 1.1 mm or less, such as the glass substrate It has a thickness of 0.5 mm to 2.0 mm, for example, the glass substrate has a thickness of 0.5 mm to 1.1 mm, for example, the glass substrate has a thickness of 0.7 mm to 1.1 mm. Although these are exemplary thicknesses, the thickness of the glass sheet can be any value including decimal places, and is in the range of 0.1 mm or more and 4.0 mm.

Embodiments described herein may provide one or more of the following advantages: The efficiency of a cadmium indium gallium selenide battery can be improved by controlling the level of alkali metal in the cell or controlling the position and time in which the alkali metal is present in the multilayer cell. For example, the process allows sodium to be present during or after growth of the cadmium indium gallium selenide film. To date, it has not been clearly known whether efficiency depends on the time during which sodium is formed in the process of forming a cadmium indium gallium selenide battery; improved efficiency can be obtained on glass of various compositions. Thus, it is permissible to use less expensive glass or glass with a higher strain point, and glass with a higher strain point allows processing at higher temperatures. This can promote processing speed or have better temperature-dependent microstructures in the obtained cadmium indium gallium selenide or molybdenum film; the processing speed can be promoted by increasing the diffusion rate of alkali metals such as sodium and potassium; A more robust, repeatable process can be formed that is less relevant to the previous experience of the sample, such as the aging effect of the glass or the cleaning, washing, grinding or polishing process of the glass; lower alkali metal content and/or Less moving alkali metal content glass will improve the shelf life of the glass prior to processing, thereby reducing inventory and allowing for a better supply chain; and/or modifying the alkali metal content in different device manufacturing processes to make specific The processing experience better maximizes battery efficiency. An example would be a 2 minute process versus a 1 hour process versus a very low level alkali metal process.

An advantage of the present disclosure over sputter deposited barrier layers is that the depletion layer is inherent to the glass system and extends the bulk of the body glass structure. This reduces the problem of any sticking or delamination due to the lack of a sharp interface between the surface layer and the body glass. An additional advantage of the depleted surface layer is that it significantly improves the chemical durability of the glass surface and prevents or minimizes the alkali metal and/or alkaline earth metal from escaping into the environment (especially water vapor) after prolonged exposure. This protection scheme will improve the electrical reliability of the photovoltaic module and allow for better light conversion efficiency during the life of the module. Modifying the glass surface by applying a voltage can also provide a means of designing the glass surface to control the transfer of the alkali metal and removing the restrictions on the composition of the body glass. This greatly increases the compositional space of the glass, which can be used to optimize other host glass properties such as coefficient of thermal expansion, strain point, melting, forming, cost, and the like.

Instance

Example 1: Two surface-sputtered gold carbonate-lime-yttria glass (SLG) were heated in air for 20 minutes to 400 ° C and held at a temperature of 10 minutes. A 50 V DC voltage is then applied across the two faces and the positive wire is on the non-tin side of the glass. After applying a voltage for 10 minutes at 400 ° C, the sample was cooled to 100 ° C in 30 minutes and the voltage was maintained at 50 volts. The voltage was then removed and the sample was allowed to cool to room temperature. The current representation from the point in time at which the voltage is applied to the sample is shown in line 26 of Figure 5 . Figure 5 is a plot of the current of the SLG-type glass as a function of time. From this data, the total Coulomb flow through the sample was calculated to be 0.042 C/cm ² and then allowed to predict the depth of depletion that would be formed. Based on the composition of the glass, assuming that the sodium distribution is square, the estimated depletion depth is 388 nm, which is shown as the area 28 below line 26 . Point 30 on line 26 represents the point at which the glass begins to cool.

The SIMS sodium distribution in the glass was taken from these measurements as illustrated in Figure 6 . Figure 6 is a graph of sodium distribution taken on the non-tin side of SLG glass by secondary ion mass spectrometry (SIMS). Line 32 illustrates the distribution of sodium on the fracture surface of the glass, line 34 illustrates the distribution of sodium on the surface of the positively biased glass after voltage treatment, and line 35 illustrates the distribution of hydrogen on the surface of the positively biased glass after voltage treatment. A depletion depth of 125 nm is produced, and then the sodium gradually increases back to the subject level.

Remove gold from a similar sample. The sample is then washed, and molybdenum is sputter coated onto the depleted surface, followed by co-evaporation deposition of cadmium indium gallium selenide on top of the molybdenum. The film was then subjected to SIMS measurements and the results are shown in Figure 7 . The picture shows a seventh example of measurement by SIMS profile sodium cadmium indium gallium selenide and a molybdenum film 1 in. Compared to the line 42 of the non-voltage treated SLG glass standard sheet, the data shows that the voltage depleted sodium-line 44 in the SLG glass surface has produced reduced levels of sodium in the molybdenum (line 36 ) and cadmium indium gallium selenide films. Line 38 represents indium (In) in the cadmium indium gallium selenide film, and line 40 represents oxygen from the glass surface.

Example 2: Sodium-free, potassium-rich and two surface sputtered gold tellurite glasses were heated in air for 20 minutes to 400 ° C and held at a temperature of 10 minutes. A 50 V DC voltage is then applied across both faces. After applying a voltage for 10 minutes at 400 ° C, the sample was cooled to 100 ° C in 30 minutes and the voltage was maintained at 50 volts. The voltage was then removed and the sample was allowed to cool to room temperature. The current expression from the point in time at which the voltage is applied to the sample is shown in Fig. 8 . Figure 8 is a graph showing the currents of an electric field of 50 volts applied to Examples 1 and 2, lines 46 and 48 , respectively. From this data, the total Coulomb flow through the sample was calculated to be 0.071 cm ² , and then the depletion depth that would be formed was estimated. Based on the composition of the glass, assuming that the sodium distribution is square, the estimated depletion depth is 388 nm, which is shown as the area 50 below line 46 . Based on the composition of the glass, assuming that the potassium distribution is square, the estimated depletion depth is 733 nm, and the area 52 below the line 48 is shown. The SIMS potassium distribution in the glass was obtained by these measurements and is shown in Fig. 9 . Line 54 illustrates the potassium cross section and line 56 illustrates the potassium distribution on the positive voltage side. A depletion of 600 nm is produced, and then potassium gradually increases back to the main level.

The gold was removed from a similar sample, then the sample was washed and the molybdenum was sputter coated onto the depleted surface, followed by co-evaporation of the deposited cadmium indium gallium selenide on top of the molybdenum. The film was then subjected to SIMS measurement and the results are shown in Fig. 10 . Figure 10 is a graph showing the potassium distribution of cadmium indium gallium selenide and molybdenum film of Example 2 by SIMS. Compared to the untreated glass standard sheet 64 , the data shows that the voltage-depleted potassium-line 60 in the glass surface has been produced in the molybdenum (line 58 ) and cadmium indium gallium selenide films (In line 66 , O line 62 ). The level of potassium is significantly reduced.

Example 3: Two surface-sputtered gold carbonate-lime-yttria glass (SLG) were heated in air for 1.5 hours to 425 ° C and held at a temperature of 10 minutes. A 25 V DC voltage is then applied across both faces. After applying a voltage for 10 minutes at 425 ° C, the voltage was turned off and the sample was cooled to 100 ° C in 8 hours and no voltage was applied. It is believed that applying a voltage pulls sodium to the surface of the (-) electrode region between gold and glass. Slow cooling is expected to allow sodium to diffuse back into the glass to enrich the surface of the glass.

SIMS is then applied to both sides of the glass sample, the (+) and (-) wires of the glass, lines 72 and 68 , respectively, and the results and the results of the untreated glass piece - line 70 are shown in Figure 11 . The positive side of the glass is still sodium depleted, while the (-) side of the glass has become rich in sodium.

Example 4: Two surface-sputtered, sodium-rich yttria glass were heated in air for 1.5 hours to 425 ° C and held at a temperature of 10 minutes, and then a DC voltage of 25 V was applied across both faces. After applying a voltage for 10 minutes at 425 ° C, the voltage was turned off and the sample was rapidly cooled to 100 ° C in 10 minutes and no voltage was applied. It was found that the applied voltage could pull sodium to the surface of the (-) electrode region between gold and glass. The sodium of the glass itself in the (-) electrode side is shown to have approximately the same sodium level as the body glass near the surface area. The sodium-depleted region on the positive electrode side of the glass reaches a depth of about 200 nm.

Figure 12 is a graph showing the sodium distribution of Example 4 by SIMS. SIMS is then applied to both sides of the glass sample, the (+) and (-) wires of the glass, lines 78 and 74 , respectively, and the resulting line 76 of the untreated glass is shown in Figure 12 . The positive side of the glass is sodium depleted.

Example 5: Two surface-sputtered gold-rich, sodium-rich yttria glass were heated in air for 1.5 hours to 425 ° C and held at a temperature of 10 minutes, and then a 5 V DC voltage was applied across both faces. After applying a voltage for 10 minutes at 425 ° C, the voltage was turned off and the sample was rapidly cooled to 100 ° C in 10 minutes and no voltage was applied. It was found that the applied voltage could pull sodium to the surface of the (-) electrode region between gold and glass. The sodium of the glass itself in the (-) electrode side is shown to have approximately the same sodium level as the body glass near the surface area. The sodium-depleted region on the positive electrode side of the glass reaches a depth of about 100 nm.

Figure 13 is a graph showing the sodium distribution of Example 5 by SIMS. SIMS is then applied to both sides of the glass sample, the (+) and (-) wires of the glass, lines 84 and 80 , respectively, and the results and the results of the untreated glass piece - line 82 are shown in Fig. 12. The positive side of the glass is sodium depleted.

Various modifications and alterations of the present invention will be apparent to those skilled in the art without departing from the scope of the invention. Therefore, it is intended that the present invention cover the modifications and variations of the invention

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Claims (23)

A method for moving an alkali metal ion in a glass substrate to form a glass substrate having an intrinsic alkali metal barrier layer, the method comprising the steps of: providing a glass substrate comprising an alkali metal ion, an alkaline earth metal ion or a combination of the above materials, and the glass substrate has at least two opposing surfaces and a thickness interposed between the surfaces; and applying a voltage to the two surfaces of the substrate such that at least a portion of the alkali metal ions, alkaline earth in at least one surface The metal ions or a combination of the above substances moves deeper into the thickness to form the glass substrate having the intrinsic alkali metal barrier layer. The method of claim 1, further comprising heating the glass substrate prior to the applying, during the applying, or prior to the applying, and during the applying. The method of claim 2, wherein the heating comprises heating at a temperature in the range of 20 ° C to 600 ° C. The method of claim 1, wherein the applying comprises applying a voltage to a molybdenum film during deposition of the cadmium indium gallium selenide. The method of claim 1, wherein the applying comprises applying a voltage to the cadmium indium gallium selenide or the molybdenum film after the deposition of the cadmium indium gallium selenide. The method of claim 5, wherein the applying comprises applying a voltage to the molybdenum film, and then heating the glass substrate and the molybdenum film to a temperature of 50 ° C or higher. The method of claim 1, wherein the applying comprises applying a voltage to the glass substrate while heating the glass substrate. The method of claim 1, wherein the intrinsic alkali metal barrier layer has a thickness from at least one surface of the glass substrate into the body of the glass substrate, the thickness being from 3 nm to 10 μm. An article comprising the glass substrate produced according to claim 1, the glass substrate having an intrinsic alkali metal barrier layer. An optoelectronic device comprising the glass substrate produced according to claim 1, the glass substrate having an intrinsic alkali metal barrier layer. The photovoltaic device of claim 9 comprising a functional layer comprising copper indium gallium diselenide or cadmium telluride adjacent to the intrinsic alkali metal barrier layer. A method of moving an alkali metal ion in a glass substrate to form a glass substrate having a reinforced alkali metal layer, the method comprising the steps of: Providing a glass substrate comprising an alkali metal ion, an alkaline earth metal ion, or a combination thereof, wherein the glass substrate has at least two opposing surfaces and a thickness interposed between the surfaces; and applying the two surfaces of the substrate The voltage is such that at least a portion of the alkali metal ion, alkaline earth metal ion, or a combination of the foregoing species in the vicinity of at least one surface moves away from a negative voltage and proceeds to a positive voltage on an opposite surface to form a layer having the reinforcing alkali metal layer. The glass substrate. The method of claim 12, further comprising heating the glass substrate prior to the applying, during the applying, or prior to the applying and during the applying. The method of claim 13, wherein the heating comprises heating at a temperature in the range of 20 ° C to 600 ° C. The method of claim 12, wherein the applying comprises applying a voltage to a molybdenum film during deposition of the cadmium indium gallium selenide. The method of claim 12, wherein the applying comprises applying a voltage to the cadmium indium gallium selenide or the molybdenum film after the deposition of the cadmium indium gallium selenide. The method of claim 16, wherein the applying comprises applying a voltage to the molybdenum film, and then heating the glass substrate and the molybdenum film to a temperature of 50 ° C or higher. The method of claim 12, wherein the applying comprises applying a voltage to the glass substrate while heating the glass substrate. The method of claim 12, wherein the reinforcing alkali metal layer has a thickness from at least one surface of the glass substrate into the body of the glass substrate, the thickness being from 3 nm to 10 μm. An article comprising the glass substrate produced in accordance with claim 12, the glass substrate having an intrinsic alkali metal barrier layer. An optoelectronic device comprising the glass substrate produced in accordance with claim 12, the glass substrate having a reinforced alkali metal layer. The photovoltaic device of claim 21, comprising a functional layer comprising copper indium gallium diselenide or cadmium telluride adjacent to the enhanced alkali metal layer. An article comprising a glass substrate having a first region of a spent alkali metal ion, an alkaline earth metal ion or a combination thereof; and an alkali metal ion, an alkaline earth metal ion or a substance having a substantially uniform concentration A second region of the combination, the second region being in physical contact with the first region, wherein the glass substrate does not have a third region having an increased concentration of alkali metal ions, alkaline earth metal ions, or a combination thereof.