阅读说明：本技术 用于改善低温下性能的太阳能电池设计 (Solar cell design for improved performance at low temperatures ) 是由 P·T·肖 C·M·菲泽 X·刘 于 2020-02-18 设计创作，主要内容包括：本发明的名称是用于改善在低温下性能的太阳能电池设计。一种包括至少一个太阳能电池的面板,该太阳能电池具有由砷化镓(GaAs)或砷化铟镓(InGaAs)组成的电池,该太阳能电池具有由p型掺杂的砷化铝镓(AlGaAs)或砷化铟铝镓(InAlGaAs)组成的背面场(BSF),用于在低于-50℃的温度下增强太阳能电池的运行。在一个实例中,背面场包括Al<Sub>x</Sub>Ga<Sub>1-x</Sub>As或In<Sub>0.01</Sub>Al<Sub>x</Sub>Ga<Sub>1-x</Sub>As,其中x小于约0.8,例如0.2。背面场可以是利用锌(Zn)或碳(C)p型掺杂的。(The name of the invention is a solar cell design for improved performance at low temperatures. A panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs), the solar cell having a Back Surface Field (BSF) comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (InAlGaAs) for use belowEnhancing the operation of the solar cell at a temperature of-50 ℃. In one example, the back surface field includes Al x Ga 1‑x As or In 0.01 Al x Ga 1‑x As, wherein x is less than about 0.8, such As 0.2. The back surface field may be p-type doped with zinc (Zn) or carbon (C).)

1. An apparatus, comprising: a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs), the solar cell having a Back Surface Field (BSF) comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (InAlGaAs) for enhancing operation of the solar cell at temperatures below about-50 ℃.

2. The device of claim 1, wherein the back surface field is formed of Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs.

3. The device of claim 2, wherein x is less than about 0.8.

4. The apparatus of claim 3, wherein x is 0.2.

5. The device of claim 1, wherein the back surface field is p-type doped with zinc (Zn) or carbon (C).

6. The device of claim 1, wherein the back surface field forms a heterojunction with an intermediate cell matrix having a lower barrier height than an intermediate cell back surface field consisting of indium gallium phosphide (GaInP).

7. The device of claim 1, wherein the back surface field forms a heterojunction with an intermediate cell body having a barrier height in the valence band of about 90meV or less.

8. The device of claim 7, wherein the barrier height allows thermalization of the majority carrier holes to be reduced to a temperature below about-50 ℃, which eliminates resistive losses associated with the barrier.

9. The apparatus of claim 7, wherein the barrier height eliminates resistive losses.

10. The device of claim 1, wherein the efficiency of the solar cell monotonically increases with decreasing temperature over a temperature range between room temperature and a temperature of about-150 ℃.

11. The apparatus according to any one of claims 1-10, further comprising: a spacecraft comprising said panel.

12. A method, comprising: fabricating a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs), the solar cell having a back surface field comprised of p-type doped aluminum gallium arsenide (AlGaAs) or aluminum gallium indium arsenide (InAlGaAs) for enhancing operation of the solar cell at temperatures below about-50 ℃.

13. The method of claim 12, wherein the back surface field is formed of Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs, wherein x is less than about 0.8.

14. The method of claim 12, wherein the back surface field is p-type doped with zinc (Zn) or carbon (C).

15. A method, comprising: generating an electrical current using a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs), the solar cell having a back surface field comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (InAlGaAs) for enhancing operation of the solar cell at temperatures below about-50 ℃.

16. The device of claim 15, wherein the back surface field is formed of Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs, wherein x is less than about 0.8.

17. An apparatus, comprising:

a panel comprising at least one solar cell having an intermediate cell (MC) matrix and an intermediate cell Back Surface Field (BSF) for enhancing operation of the solar cell at temperatures below about-50 ℃;

wherein the substrate is composed of gallium arsenide (GaAs) or indium gallium arsenide (GaInAs) and the back surface field is composed of a material such that:

the back surface field has a valence band offset of less than about 100meV relative to the substrate;

the back surface field has a type I or type II band arrangement with respect to the substrate; and is

The back surface field maintains a conduction band offset greater than 0meV with respect to the substrate so that the back surface field acts as a heteropassivation layer and reflects minority carrier electrons back to the p-n junction for collection.

18. The device of claim 17, wherein the lattice constant of the back surface field is about the same as the lattice constant of the intermediate cell substrate.

19. The device of claim 17, wherein the back surface field is formed of aluminum gallium arsenide (Al)_xGa_1-xAs) wherein x is less than about 0.8.

20. The device of claim 17, wherein the back surface field is formed of aluminum gallium indium arsenide (Al)_xGa_1-x-yIn_yAs) where x is less than about 0.8, and y is selected so that the lattice constant of the back surface field is about the same As the lattice constant of the substrate.

21. The device of claim 17, wherein the back surface field is formed of aluminum gallium antimony arsenide (Al)_xGa_1-xAs_1-ySb_y) A composition wherein x is less than about 0.8, and y is selected to match a type I or type II band alignment with respect to the matrix.

Technical Field

The present disclosure relates generally to solar cell designs for improved performance at low temperatures.

Background

While standard solar cells are used in tasks that operate near or above room temperature, many new applications for solar cells now require operation at temperatures well below-50 ℃.

For example, UAVs (unmanned aerial vehicles) can operate at altitudes in excess of 50,000 feet at temperatures approaching-70 ℃. In another example, a deep space exploration for Jupiter and Saturn was run between-140 to-165 ℃.

Therefore, solar cell performance at low temperatures is critical for these increasingly common applications. Unfortunately, many solar cells are optimized for performance near room temperature, with significant loss of performance at low temperatures.

Therefore, there is a need for a solar cell design for devices optimized for operation at temperatures below about-50 ℃.

Disclosure of Invention

The present disclosure describes an apparatus, comprising: a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs) with a Back Surface Field (BSF) comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (inalgas) for enhancing solar cell operation at temperatures below about-50 ℃.

The back surface field may comprise Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs, wherein x is less than about 0.8, e.g., wherein x is 0.2. The back surface field may be p-doped with zinc (Zn) or carbon (C).

The back surface field may form a heterojunction with an intermediate cell (MC) matrix having a lower barrier height than an intermediate cell back surface field composed of indium gallium phosphide (GaInP).

The back surface field can form a heterojunction with an intermediate cell body having a barrier height of about 90meV or less in the valence band. The barrier height allows thermalization of the majority carrier holes down to temperatures below about-50 ℃, which eliminates resistive losses associated with the barrier. The barrier height eliminates resistive losses.

In the temperature range between room temperature and a temperature of about-150 ℃, the efficiency of the solar cell increases monotonically with decreasing temperature.

The present disclosure also describes a method comprising: a panel is fabricated comprising at least one solar cell having an intermediate cell back surface field comprised of zinc doped aluminum gallium arsenide for enhancing operation of the solar cell at temperatures below about-50 ℃.

Further, the present disclosure describes a method comprising: generating an electric current using a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs) with a back surface field comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (inalgas) for enhancing the operation of the solar cell at temperatures below about-50 ℃.

Finally, the present disclosure describes an apparatus comprising: a panel comprising at least one solar cell having an intermediate cell matrix and an intermediate cell back surface field for enhancing solar cell operation at temperatures below about-50 ℃; wherein the substrate is composed of gallium arsenide (GaAs) or indium gallium arsenide (GaInAs) and the back surface field is composed of a material such that: the back surface field has a valence band offset of less than about 100meV relative to the substrate; the back surface field has a type I or type II band arrangement with respect to the substrate; and the back surface field maintains a conduction band offset greater than about 0meV with respect to the substrate so that the back surface field acts as a hetero-step passivation layer and reflects minority carrier electrons back to the p-n junction for collection.

The lattice constant of the basal plane field may be about the same as the lattice constant of the intermediate cell substrate.

The back surface field may be made of Al_xGa_1-xAs, wherein x is less than about 0.8.

The back surface field may be formed of aluminum gallium indium arsenide (Al)_xGa_1-x-yIn_yAs) where x is less than about 0.8, and y is selected so that the lattice constant of the back surface field is about the same As the lattice constant of the substrate.

The back surface field may be formed of aluminum gallium antimony arsenide (Al)_xGa_{1- x}As_1-ySb_y) A composition wherein x is less than about 0.8, and y is selected to match a type I or type II band alignment with respect to the matrix.

In each case, the spacecraft may comprise the panel.

Drawings

Referring now to the drawings in which like reference numbers represent corresponding parts throughout:

fig. 1 is a layer schematic of a triple junction solar cell illustrating the baseline solar cell of fig. 1 (left) and the new solar cell of fig. 1 (right).

Fig. 2 is a graph of the LIV (light-current-voltage) curve measured from-150 ℃ to 30 ℃ for a baseline solar cell.

Figures 3A and 3B are graphs providing a comparison of the back surface field of new and baseline solar cells with the bandgap diagram of the bulk heterojunction.

Fig. 4A, 4B and 4C are diagrams showing possible band arrangements for different material cases for improving low temperature performance.

Fig. 5 is a graph of the LIV curve measured from-150 ℃ to 30 ℃ for a new solar cell.

Fig. 6 is a graph of the maximum power of the back surface field of the baseline and new solar cells as a function of temperature.

Fig. 7A illustrates a method of manufacturing a solar cell, a solar cell panel, and/or a satellite.

Fig. 7B illustrates the resulting satellite with a solar cell panel comprised of solar cells.

Fig. 8 is an illustration of a solar cell panel in the form of a functional block diagram.

Detailed Description

In the following description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural changes may be made without departing from the scope of the present disclosure.

Overview

The present disclosure describes design rules for solar cells for improving solar cell performance at low temperatures (e.g., below-50 ℃).

In particular, a major limitation in low temperature performance is the presence of heterojunction resistance, which increases exponentially with decreasing temperature. The major heterojunction resistance in a standard triple junction (3J) solar cell occurs between the intermediate cell matrix and the BSF. The offset of the material in the valence band acts as a rectifying diode. At nominal operating temperatures, the potential barrier is easily overcome by the photo-generated holes collected in the circuit. At low temperatures, the interruption or heterodyning of the valence band energy acts as a rectifying barrier.

Previous attempts have been made to solve this problem of 3J solar cell performance at low temperatures.

One attempt was to use standard 3J space solar cells at low temperatures and tolerate any low temperature performance degradation.

Another attempt is to change the p-type doping in the intermediate cell matrix near the interface with the intermediate cell BSF. The variation in doping can narrow the width of the heterojunction barrier, allowing for increased tunneling transport through the heterojunction barrier and lowering the heterojunction resistance. This alleviates the problem, but is at best vulnerable depending on temperature and exact doping level.

The present disclosure reduces this heterojunction resistance by replacing the baseline BSF material to reduce, eliminate, or redirect the heterojunction barrier. Specifically, one example described in this disclosure describes a new solar cell having an intermediate cell BSF composed of AlGaAs or inalgas for improving solar cell performance at temperatures below about-50 ℃. In one example, the new BSF includes Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs, where x is 0.2.

Experimental data show that the efficiency of the new BSF is increased by 25% at-150 ℃ relative to the baseline BSF. In fact, the new solar cell performance is 20-30% higher than the baseline solar cell.

Description of the technology

Fig. 1 is a schematic layer diagram, each showing a cross-section of a device comprising a baseline and new III-V3J solar cell 100a, 100b, respectively.

Fig. 1 (left) shows a baseline III-V3J solar cell 100a as currently fabricated. The solar cell 100a includes a 5-15m Ω p-doped germanium (p-Ge) substrate 102 on which a standard (std) nucleation layer 104 is deposited and/or fabricated, a buffer layer 106, a lower tunnel junction 108, a Zn-doped GaInP BSF110 a, a Middle Cell (MC) composed of a GaInAs matrix 112 and InGaAs emitter 114, an MC window 116, a top tunnel junction 118, a Top Cell (TC) BSF 120 composed of GaInP, a TC 122 composed of GaInP, an aluminum indium phosphide (AlInP) window 124, and a GaInAs cap 126.

Fig. 1 (right panel) shows a new III-V3J solar cell 100b according to the present disclosure, in which GaInP BSF110 a in the middle cell of the baseline solar cell 100a is replaced with Zn p-doped AlGaAs BSF110 b. In one example, the BSF110b includes Al_xGa_1-xAs, where x is 0.2. In alternative examples, the BSF110b may include In_0.01Al_xGa_1-xAs, where x is 0.2. In an alternative example, the BSF110b may be p-type doped with carbon (C). The solar cells 100a, 100b may include other features not illustrated to simplify the drawing, such as anti-reflective coatings, front and back metal contacts, and the like.

Fig. 2 is a graph of current (a) versus voltage (V) illustrating the results of using GaInP BSF110 a in the middle cell of baseline solar cell 100 a. The LIV curve performs well from room temperature down to-50 deg.C, with linear behavior around Voc (open circuit voltage). Efficiency increases with decreasing temperature in this range due to increasing Voc. However, for temperatures below-50 ℃, LIV shows non-linearity near Voc. These nonlinearities lead to a loss in fill factor and a significant loss in the performance of the solar cell 100 a. This non-linearity is caused by the leaky diode rectification.

Fig. 3A and 3B are graphs providing a comparison of bandgap diagrams of AlGaAs BSF110B and GaInP BSF110 a, both of which form a heterojunction with a GaInAs matrix 112.

As shown in fig. 3A, modeling indicates that AlGaAs BSF110b forms a heterojunction with the intermediate cell matrix 112 having a lower barrier height of about 90meV or less in the valence band, as compared to GaInP BSF110 a. The lower barrier height allows for thermalization of the majority carrier holes to a much lower temperature, i.e., a temperature below about-50 ℃, which eliminates the resistive losses associated with the barrier.

As shown in fig. 3B, GaInP BSF110 a forms a significantly higher heterojunction barrier height of 300meV in the valence band. At temperatures above-50 ℃, there is sufficient thermal energy for the majority carrier holes to thermalize to cross the barrier. At temperatures below-50 ℃, there is insufficient thermal energy, resulting in heterojunction resistance that behaves in a non-linear fashion in the solar cell 100a LIV curve around Voc. Therefore, increasing the doping does not eliminate this problem.

FIGS. 4A, 4B, and 4C are graphs showing possible ribbon arrangements for different material cases for improved low temperature performance (e.g., below-50℃.).

Fig. 4A shows a similar situation as fig. 3A, with a type I offset, where the valence band is close to that of the base material and a small offset of less than 100meV is obtained. This limitation is very important because at temperatures below-50 c, the hole energy to overcome the barrier is no more than about five times the standard thermal energy of kT or 19.3meV at-50 c.

Fig. 4B shows a possible design in which no shift occurs in the valence band between the substrate and the BSF.

Fig. 4C shows a possible design where the offset is type II and there is a negative offset and the BSF valence band energy is higher than the valence band energy of the matrix material. Furthermore, there is a limit to approximately 100meV for the type II band aligned material, since heterograding shift will form a rectifying barrier.

The actual energy levels of BSF materials vary with material selection and are well known to those skilled in the art of III-V semiconductor devices. The BSF material for GaAs or GaInAs bulk sub-cells is preferably selected from materials that comply with the following main criteria: first, they must have a valence band offset of less than 100 meV; secondly, they may be type I or type II ribbon arrangements with respect to the substrate; and third, they must maintain a band offset to the conduction band of greater than 0meV so that they continue to act as heteropassivation layers and reflect minority carrier electrons from the interface and back to the p-n junction for collection.

Finally, if the lattice constant of the BSF is close to or about the same as the lattice constant of the substrate, the choice of material is excellent. This criterion allows the minimum number of defects to be generated at the interface, and the BSF reduces the interface recombination velocity of minority carriers.

For GaAs and GaInAs as examples, the best choice of BSF material may be selected from: al (Al)_xGa_1-xAs, wherein x is less than 0.8; al (Al)_xGa_1-x-yIn_yAs, where x is less than 0.8, and y is selected to allow the alloy BSF to approximately match the matrix material lattice constant; al (Al)_xGa_1-xAs_1-ySb_yWherein x is less than 0.8, and y is selected to match a type I or type II arrangement. Various other combinations may be selected from the group consisting of multicomponent alloys of GaNAs, AlGaAs, AlGaAsSb, AlGaPAs, AlGaPAsSb, AlGaInAs, algainpasb, AlGaAsBi, algapasbi, BGaAs, BAlGaAs, BAlGaInAs, etc., and further examples of material alloys of the above combinations. Further combinations of subcells for other matrix materials may be proposed, such as GaInP, AlGaInP, AlGaInAs, GaInNAs, GaInNAsSb, inp gaipainas and GaAsSb, as long as the above criteria are followed.

Fig. 5 is a graph of current (a) versus voltage (V) illustrating the effect of a lowered heterojunction barrier on the performance of a new solar cell 100 b. The new solar cell 100b with AlGaAs BSF110b shows a well-performing LIV curve, especially near Voc, down to the lowest measured temperature of-150 ℃, compared to the baseline solar cell 100a with GaInP BSF110 a illustrated in fig. 2. The new solar cell 100b with AlGaAs BSF110b still exhibits Voc that increases with decreasing temperature.

FIG. 6 is the maximum power (mW/cm)²) A graph with respect to temperature (C) compares a baseline solar cell 100a with GaInP BSF110 a with a new solar cell 100b with AlGaAs BSF110 b.

For the case of GaInP BSF110 a, the efficiency increases due to the increase in voltage of the baseline solar cell 100a from room temperature to-50 ℃. At temperatures from-50 ℃ to-150 ℃, the efficiency of the baseline solar cell 100a decreases with decreasing temperature due to high heterojunction resistance and associated non-linearity near Voc.

For the case of AlGaAs BSF110b, the efficiency of the new solar cell 100b monotonically increases with decreasing temperature for a temperature range between room temperature of about 20 ℃ to 30 ℃ and a temperature of about-150 ℃. Starting from-50 ℃, this contrasting behavior leads to differences in low temperature battery performance. The difference in efficiency of the new solar cell 100b at-150 ℃ is 25%, which is a significant improvement over the solar cells 100a, 100b operating under these conditions.

Alternatives and modifications

The description set forth above has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the examples described. Many alternatives and modifications can be used in place of the specific description set forth above.

For example, while AlGaAs and InAlGaAs are the most studied materials to date, a variety of other possible materials may be used. Al may be used_0.2Ga_0.8AlGaAs and In other than As_0.01Al_0.2Ga_0.8Compositions of InAlGaAs other than As, and InGaAsP alloys lattice-matched to Ge/GaAs substrates.

In another example, although this disclosure describes a widely adopted triple junction solar cell, it can be extended to cover any example of a single junction, double junction, or other multi-junction solar cell designed to include materials for majority carriers to reduce heterojunction resistance. This would include any BSF to substrate or window to emitter transition for the valence or conduction band, respectively.

In yet another example, while the present disclosure generally describes the new solar cell 100b, and the BSF110b, particularly alternatives as including certain materials may describe the new solar cell 100b and the BSF110b as consisting of, or consisting essentially of, these or other materials.

Similarly, while the present disclosure describes the new solar cell 100a as operating in a desired manner at a temperature of about-50 ℃ or less, alternatives may describe the new solar cell 100 as operating at a temperature of about-100 ℃ or less, -150 ℃ or less, or other lower temperatures.

Aerospace applications

Examples of the present disclosure may be described in the context of a method 700 of manufacturing solar cells, solar cell panels, and/or aerospace vehicles, such as satellites, as shown in FIG. 7A, the method 700 including a step 702 714 where a resulting satellite 716, comprised of various systems 718 and bodies 720, is shown in FIG. 7B, which includes a panel 722 comprised of an array 724 of one or more solar cells 100B.

As illustrated in FIG. 7A, during pre-production, exemplary method 700 may include specification and design 702 of satellite 716, and material procurement 704 therefor. During production, component and subassembly fabrication 706 of satellite 716 and system integration 708, including fabrication of satellite 716, panel 722, array 724, and solar cell 100b, occurs. Thereafter, the satellite 716 may be authenticated and delivered 710 to be placed into service 712. The satellites 716 may also be scheduled for maintenance and service 714 (including modification, reconfiguration, refurbishment, and so on) prior to transmission.

Each of the processes of method 700 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For purposes of this description, a system integrator may include, but is not limited to, any number of manufacturers and major-system subcontractors; the third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers; and the operator may be a satellite company, military entity, service organization, etc.

As shown in fig. 7B, a satellite 716 manufactured by the exemplary method 700 may include a variety of systems 718 and bodies 720. Examples of systems 718 included with satellite 716 include, but are not limited to, one or more of a propulsion system 726, an electrical system 728, a communication system 730, and a power system 732. Any number of other systems may also be included.

Functional block diagram

Fig. 8 is an illustration of a panel 722 in the form of a functional block diagram, according to an example. The panel 722 is comprised of an array 724, the array 724 being comprised of one or more solar cells 100b individually attached to the panel 722. At least one solar cell 100b has an AlGaAs BSF110 b. Each solar cell 100b absorbs light 800 from a light source 802 and produces an electrical output 804 in response thereto.

Further, the present disclosure includes examples according to the following clauses:

clause 1. an apparatus, comprising: a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs), the solar cell having a Back Surface Field (BSF) comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (InAlGaAs) for enhancing operation of the solar cell at temperatures below about-50 ℃.

Clause 2. the device according to clause 1, wherein the back surface field is made of Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs.

Clause 3. the apparatus of clause 2, wherein x is less than about 0.8.

Clause 4. the apparatus of clause 3, wherein x is 0.2.

Clause 5. the device according to any one of clauses 1-4, wherein the back surface field is p-type doped with zinc (Zn) or carbon (C).

Clause 6. the device according to any of clauses 1-5, wherein the back surface field forms a heterojunction with an intermediate cell matrix having a lower barrier height than an intermediate cell back surface field consisting of indium gallium phosphide (GaInP).

Clause 7. the device according to any of clauses 1-6, wherein the back surface field forms a heterojunction with an intermediate cell matrix having a barrier height in the valence band of about 90meV or less.

Clause 8. the device according to clause 7, wherein the barrier height allows thermalization of the majority carrier holes to a temperature below about-50 ℃, which eliminates resistive losses associated with the barrier.

Clause 9. the apparatus according to clause 7 or 8, wherein the barrier height eliminates resistive losses.

Clause 10. the device according to any one of clauses 1-9, wherein the efficiency of the solar cell monotonically increases with decreasing temperature in a temperature range between room temperature and a temperature of about-150 ℃.

Clause 11. the apparatus of any one of clauses 1-10, further comprising: a spacecraft comprising such a panel.

Clause 12. a method, comprising: a panel is fabricated including at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs) with a back surface field comprised of p-type doped aluminum gallium arsenide (AlGaAs) or aluminum gallium indium arsenide (inalgas) for enhancing operation of the solar cell at temperatures below about-50 ℃.

Clause 13. the method according to clause 12, wherein the back surface field is made of Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs, wherein x is less than about 0.8.

Clause 14. the method according to clause 12 or 13, wherein the back surface field is p-type doped with zinc (Zn) or carbon (C).

Clause 15. a method, comprising: generating an electric current using a panel comprising at least one solar cell having a cell comprised of gallium arsenide (GaAs) or indium gallium arsenide (InGaAs) with a back surface field comprised of p-type doped aluminum gallium arsenide (AlGaAs) or indium aluminum gallium arsenide (inalgas) for enhancing the operation of the solar cell at temperatures below about-50 ℃.

Clause 16. the device according to clause 15, wherein the back surface field is made of Al_xGa_1-xAs or In_0.01Al_xGa_1-xAs, wherein x is less than about 0.8.

Clause 17. an apparatus, comprising: a panel comprising at least one solar cell having an intermediate cell (MC) matrix and an intermediate cell Back Surface Field (BSF) for enhancing operation of the solar cell at temperatures below about-50 ℃; wherein the substrate is composed of gallium arsenide (GaAs) or indium gallium arsenide (GaInAs) and the back surface field is composed of a material such that: the back surface field has a valence band offset of less than about 100meV relative to the substrate; and the back surface field has a type I or type II band arrangement with respect to the substrate; and the back surface field maintains a conduction band offset greater than 0meV with respect to the substrate so that the back surface field acts as a heteropassivation layer and reflects minority carrier electrons back to the p-n junction for collection.

Clause 18. the device according to clause 17, wherein the lattice constant of the back surface field is about the same as the lattice constant of the intermediate cell matrix.

Clause 19. the device according to clause 17 or 18, wherein the back surface field is formed of aluminum gallium arsenide (Al)_xGa_1-xAs) wherein x is less than about 0.8.

Clause 20. the device according to any of clauses 17-19, wherein the back surface field is composed of aluminum gallium indium arsenide (Al)_xGa_{1-x- y}In_yAs) where x is less than about 0.8, and y is selected so that the lattice constant of the back surface field is about the same As the lattice constant of the substrate.

Clause 21. the device according to any of clauses 17-19, wherein the back surface field is formed of aluminum gallium antimony arsenide (Al)_xGa_{1- x}As_1-ySb_y) A composition wherein x is less than about 0.8, and y is selected to match a type I or type II band alignment with respect to the matrix.