A wide-spectrum response GaAs heterojunction solar cell based on InN nanocolumn interface modulation and preparation thereof

Abstract

The application belongs to the technical field of solar cells, and discloses a wide-spectrum response GaAs heterojunction solar cell based on InN nanocolumn interface modulation and preparation thereof. The solar cell comprises, from bottom to top, a back electrode, an InGaP back field layer, a GaAs substrate layer, an InN nanocolumn layer, a hole transport layer, a front electrode and an anti-reflection ARC layer; the InN nanocolumn serves as an interface layer of the GaAs heterojunction solar cell. The application further discloses a preparation method of the solar cell. The InN nanocolumn is used as the interface layer of the GaAs heterojunction solar cell, so that the lattice mismatch is relieved and the carrier recombination loss is reduced; meanwhile, the micro-nano structure design of the InN nanocolumn and the narrow-band gap characteristics synergize to widen the spectrum response range, enhance the light absorption and improve the photoelectric conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of GaAs solar cell technology, specifically relating to a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation and its fabrication method. Background Technology

[0002] In recent years, GaAs (gallium arsenide) solar cells have been widely used due to their advantages such as direct bandgap, excellent photoelectric conversion efficiency, and radiation resistance. According to the Shockley-Queisser model, the photoelectric conversion efficiency of a single-junction GaAs solar cell can reach 30%. However, due to various limitations such as interfacial carrier recombination, narrow spectral absorption range, and weak light absorption, the efficiency of currently fabricated GaAs solar cells still falls short of the theoretical value.

[0003] To improve the photoelectric conversion efficiency of GaAs solar cells, common methods include enhancing sunlight absorption and reducing carrier loss through optical and electrical management engineering, thereby improving the device's photoelectric conversion efficiency. Therefore, the light-trapping effect of micro / nano structures and interface management engineering of solar cells have received widespread attention. CN202111526602.7 discloses a GaAs nanocone Schottky junction solar cell and its fabrication method, mentioning a method of obtaining GaAs nanocones using ICP equipment with BCl3 gas and oxygen. This method directly etches the GaAs substrate, which can easily damage the GaAs substrate. The BCl3 and high-purity oxygen gases used are hazardous. Furthermore, although this method can enhance light absorption to some extent, it does not solve the problems of narrow spectral absorption range and interface carrier loss in GaAs solar cells. Summary of the Invention

[0004] To overcome the problems of interfacial carrier recombination and narrow spectral absorption range in existing GaAs heterojunction solar cells, this invention provides a broadband-response GaAs heterojunction solar cell based on InN nanopillar interface modulation and its fabrication method. This invention uses InN nanopillars as the interfacial modulation layer of the GaAs heterojunction solar cell, which can effectively broaden the spectral response range, enhance light absorption, and improve photoelectric conversion efficiency.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation includes, from bottom to top, a back electrode, an InGaP back field layer, a GaAs substrate layer, an InN nanopillar layer, a hole transport layer, a front electrode, and an anti-reflection ARC layer.

[0007] The back electrode is Au; the front electrode is Ag.

[0008] The InGaP back field layer is n-type with a thickness of 30–60 μm and a Si doping concentration of (1–3) × 10⁻⁶. 17 / cm 3 .

[0009] The GaAs substrate is an n-type GaAs substrate with a thickness of 250–350 μm and a Si doping concentration of (1–3) × 10⁻⁶. 18 / cm 3 The crystal plane is (110).

[0010] The InN nanopillar layers have a height of 50–200 nm and a diameter of 20–80 nm.

[0011] InN nanopillars serve as the interface layer for GaAs heterojunction solar cells, with the front electrodes positioned at both ends of the hole transport layer.

[0012] The hole transport layer is a conductive and light-transmitting carbon material, including one or more of graphene, Mxene, carbon nanotubes, and carbon quantum dots, preferably carbon nanotubes.

[0013] The method for preparing the InN nanopillar layer is as follows: an InGaP back field layer / GaAs substrate is placed in an MBE growth chamber, the temperature of the In source and Ga source is increased, and the Ga source enters the growth chamber to pre-deposit a layer of Ga source on the GaAs substrate; the Ga source is turned off, and the In source and N source enter the growth chamber to grow InN nanopillars on the GaAs substrate.

[0014] The method for fabricating a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation includes the following steps:

[0015] 1) Place the InGaP / GaAs substrate into the MBE growth chamber, raise the temperature of the In source and Ga source, pre-deposit a Ga source layer on the GaAs substrate, and then grow and prepare InN nanopillars to form an InN nanopillar layer.

[0016] 2) A back electrode is deposited on the back side of the InGaP / GaAs substrate and annealed to form an ohmic contact;

[0017] 3) A hole transport layer is fabricated on the front side of the InN nanopillar layer;

[0018] 4) A front electrode is deposited at both ends of the hole transport layer, and an anti-reflection layer ARC is deposited on the hole transport layer not covered by the front electrode to obtain a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation.

[0019] The InGaP back field layer mentioned in step 1) is n-type with a thickness of 30–60 μm and a Si doping concentration of (1–3) × 10⁻⁶. 17 / cm 3 The GaAs absorber layer is an n-type GaAs substrate with a thickness of 250–350 μm and a Si doping concentration of (1–3) × 10⁻⁶. 18 / cm 3 The crystal plane is (110). The temperature of the Ga source is 850℃~900℃, and the deposition time of the Ga source in the growth chamber is 1~5min. At this time, the temperature of the substrate is 350-450℃.

[0020] The growth temperature of the InN nanopillars is 350℃~450℃ (the temperature of the In source is 780℃~820℃; after Ga source deposition, the Ga source baffle is closed, and the In and N sources are turned on to deposit the InN nanopillars, at which time the substrate temperature is 350~450℃), the plasma source power is 200W~400W, the N2 flux is 0.7~2sccm; the growth time is 1~3h, the height of the nanopillars is 50~200nm, and the diameter is 20~80nm.

[0021] The back electrode mentioned in step 2) is an Au electrode with a thickness of 100-120 nm, an annealing temperature of 300-330 °C, and an annealing time of 15-30 s.

[0022] The hole transport layer mentioned in step 3) is a conductive and transparent carbon material, including one or more of graphene, Mxene, carbon nanotubes, and carbon quantum dots; the hole transport layer is prepared into a thin film by vacuum filtration or by wet transfer of materials, and the thickness is 100-200 nm.

[0023] The front electrode mentioned in step 4) is an Ag electrode with a thickness of 100-120 nm; the anti-reflective layer ARC is one or more of WO3, MgF2, and MoO3 thin films with a thickness of 10-30 nm.

[0024] This invention uses InN nanopillars grown on GaAs substrates as the interface modulation layer for GaAs heterojunction solar cells, which can alleviate lattice mismatch and reduce carrier recombination loss. At the same time, the synergistic effect of the micro-nano structure design of InN nanopillars and their narrow bandgap characteristics broadens the spectral response range, enhances light absorption, and improves photoelectric conversion efficiency.

[0025] The InN nanopillar layer of this invention serves as an interface between GaAs and the hole transport layer. Its micro / nano structure helps enhance light absorption, reduce reflection, and passivate the interface, reducing carrier recombination at the interface. Simultaneously, the InN nanopillars have a narrow bandgap, which broadens the spectral absorption range, including the infrared spectrum, enhancing the efficient utilization of sunlight. This also improves hole transport efficiency, allowing more hole carriers to reach the hole transport layer.

[0026] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0027] In GaAs solar cells, this invention grows InN nanopillars as an interface modulation layer. The vertical growth mode of the InN nanopillars can alleviate lattice mismatch and reduce interface carrier loss. Furthermore, InN has a band gap of 0.7 eV, allowing it to absorb near-infrared light (a wavelength range that GaAs cannot respond to), thus broadening the spectral response range of the solar cell. Simultaneously, the micro / nano light-trapping effect of the InN nanopillars enhances light absorption. Using InN nanopillars as the interface modulation layer in solar cells, the synergistic effect of micro / nano structure design and narrow band gap characteristics effectively improves the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the GaAs heterojunction cell structure with InN nanopillars grown on a GaAs substrate as the interface modulation layer in Example 1; 1-back electrode, 2-InGaP back field layer, 3-GaAs substrate layer, 4-InN nanopillar layer, 5-hole transport layer, 6-front electrode, 7-anti-reflection ARC layer.

[0029] Figure 2 This is a cross-sectional SEM image of the InN nanopillars grown on the GaAs substrate obtained in Example 1.

[0030] Figure 3 The image shows the IV curves of the solar cells of Example 1 and Comparative Example 1. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.

[0032] A GaAs heterojunction solar cell based on InN nanopillar interface modulation is shown in the schematic diagram below. Figure 1 As shown, from bottom to top, it includes a back electrode 1, an InGaP back field layer 2, a GaAs substrate layer 3, an InN nanopillar layer 4, a hole transport layer 5, a front electrode 6, and an anti-reflection ARC layer 7.

[0033] InN nanopillars serve as the interface layer for GaAs heterojunction solar cells, with the front electrodes positioned at both ends of the hole transport layer.

[0034] The back electrode is Au; the front electrode is Ag.

[0035] The InGaP back field layer is n-type with a thickness of 30–60 μm and a Si doping concentration of (1–3) × 10⁻⁶. 17 / cm 3 .

[0036] The GaAs substrate is an n-type GaAs substrate with a thickness of 250–350 μm and a Si doping concentration of (1–3) × 10⁻⁶. 18 / cm 3 The crystal plane is (110).

[0037] The InN nanopillar layers have a height of 50–200 nm and a diameter of 20–80 nm.

[0038] The hole transport layer is a conductive and light-transmitting carbon material, including one or more of graphene, Mxene, carbon nanotubes, and carbon quantum dots, preferably carbon nanotubes.

[0039] InN nanopillars serve as the interface layer for GaAs heterojunction solar cells, with the front electrodes positioned at both ends of the hole transport layer.

[0040] The method for preparing the InN nanopillar layer is as follows: an InGaP back field layer / GaAs substrate is placed in an MBE growth chamber, the temperature of the In source and Ga source is increased, and the Ga source enters the growth chamber to pre-deposit a layer of Ga source on the GaAs substrate; the Ga source is turned off, and the In source and N source enter the growth chamber to grow InN nanopillars on the GaAs substrate.

[0041] The thickness of the Au electrode is 100–120 nm. The thickness of the front Ag electrode is 100–120 nm; the anti-reflective layer ARC is one or more of WO3, MgF2, and MoO3 thin films, with a thickness of 10–30 nm.

[0042] Example 1

[0043] A method for fabricating a GaAs heterojunction solar cell based on InN nanopillar interface modulation includes the following steps:

[0044] 1) An n-type InGaP / GaAs substrate is used, with an InGaP layer thickness of 50 μm and a Si doping concentration of 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶.18 / cm 3 The crystal plane is (110). It is placed in the MBE growth chamber. The temperature of the In source and Ga source is increased. The Ga source baffle is opened and it enters the growth chamber. A layer of Ga source is pre-deposited on the substrate. The temperature of the Ga source is 850℃ and the deposition time is 3min. The substrate temperature is 400℃. Then the Ga source baffle is closed and the baffles of the In source and N source are opened. The In source and N source enter the growth chamber to grow and prepare InN nanopillars. The growth temperature is 400℃, the In source temperature is 800℃, the plasma source power is 400W, and the N2 flux is 1sccm. The growth time is 2h, the height of the nanopillar is 100nm, and the diameter is 50nm.

[0045] 2) An Au electrode is deposited on the back side of the InGaP / GaAs substrate and annealed to form an ohmic contact. The thickness of the Au electrode is 120 nm, the annealing temperature is 330 °C, and the annealing time is 30 s.

[0046] 3) A hole transport layer was prepared on the front side of the InN nanopillars, and a carbon nanotube film with a thickness of 100 nm was prepared by vacuum filtration.

[0047] 4) A front Ag electrode and an anti-reflection layer ARC are deposited on the hole transport layer. The thickness of the Ag electrode is 100 nm; the thickness of the anti-reflection layer ARC is WO3 and is 15 nm, thus obtaining a GaAs heterojunction solar cell based on InN nanopillar interface modulation.

[0048] Figure 2 This is a cross-sectional SEM image of the InN nanopillars grown on the GaAs substrate obtained in Example 1.

[0049] Example 2

[0050] A method for fabricating a GaAs heterojunction solar cell based on InN nanopillar interface modulation includes the following steps:

[0051] 1) An n-type InGaP / GaAs substrate is used, with an InGaP layer thickness of 50 μm and a Si doping concentration of 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm 3The crystal plane is (110). It is placed in the MBE growth chamber. The temperature of the In source and Ga source is increased. The Ga source baffle is opened and it enters the growth chamber. A layer of Ga source is pre-deposited on the substrate. The temperature of the Ga source is 900℃ and the deposition time is 2min. The substrate temperature is 410℃. Then the Ga source baffle is closed and the baffles of the In source and N source are opened. The In source and N source enter the growth chamber to grow and prepare InN nanopillars. The growth temperature is 410℃, the In source temperature is 800℃, the plasma source power is 400W, and the N2 flux is 1.5sccm. The growth time is 1.5h, the height of the nanopillar is 80nm, and the diameter is 40nm.

[0052] 2) An Au electrode is deposited on the back side of the InGaP / GaAs substrate and annealed to form an ohmic contact. The thickness of the Au electrode is 120 nm, the annealing temperature is 330 °C, and the annealing time is 30 s.

[0053] 3) A hole transport layer was prepared on the front side of the InN nanopillars, and a carbon nanotube film with a thickness of 100 nm was prepared by vacuum filtration.

[0054] 4) A front Ag electrode and an anti-reflection layer ARC are deposited on the hole transport layer. The thickness of the Ag electrode is 100 nm. The thickness of the anti-reflection layer ARC is MgF2 and is 20 nm, thus obtaining a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation.

[0055] Comparative Example 1

[0056] 1) An n-type InGaP / GaAs substrate is used, with an InGaP layer thickness of 50 μm and a Si doping concentration of 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm 3 The crystal plane is (110);

[0057] 2) An Au electrode is deposited on the back side of the InGaP / GaAs substrate and annealed to form an ohmic contact. The thickness of the Au electrode is 120 nm, the annealing temperature is 330 °C, and the annealing time is 30 s.

[0058] 3) A hole transport layer is prepared on the front side, and a carbon nanotube film with a thickness of 100 nm is prepared by vacuum filtration membrane preparation method;

[0059] 4) A front Ag electrode and an anti-reflection layer ARC are deposited on the hole transport layer. The thickness of the Ag electrode is 100 nm; the thickness of the anti-reflection layer ARC is WO3 and is 15 nm, thus obtaining a solar cell.

[0060] Comparative Example 2

[0061] 1) An n-type InGaP / GaAs substrate is used, with an InGaP layer thickness of 50 μm and a Si doping concentration of 1 × 10⁻⁶. 17 / cm 3 The GaAs thickness is 350 μm, and the Si doping concentration is 1 × 10⁻⁶. 18 / cm 3 The crystal plane is (110);

[0062] 2) An Au electrode is deposited on the back side of the InGaP / GaAs substrate and annealed to form an ohmic contact. The thickness of the Au electrode is 120 nm, the annealing temperature is 330 °C, and the annealing time is 30 s. A 2 nm thick Al2O3 film is deposited on the front side of the InGaP / GaAs substrate as an interface passivation layer.

[0063] 3) A hole transport layer was prepared on the front side of the Al2O3 film, and a carbon nanotube film with a thickness of 100 nm was prepared by vacuum filtration.

[0064] 4) A front Ag electrode and an anti-reflection layer ARC are deposited on the hole transport layer. The thickness of the Ag electrode is 100 nm; the thickness of the anti-reflection layer ARC is WO3 and is 15 nm, thus obtaining a GaAs heterojunction solar cell.

[0065] Table 1 shows a comparison of the device parameters of the solar cell prepared in Example 1 with those prepared in Comparative Examples 1 and 2. The IV curves of the solar cells in Example 1, Comparative Examples 1 and 2 are shown in the figure. Figure 3 As shown.

[0066] Table 1 Performance parameters of solar cells prepared in Example 1 and Comparative Example 1

[0067] <![CDATA[Jsc(mA / cm 2 )]]> 29.10 21.58 24.23 V(v) 0.76 0.75 0.75 PCE (%) 16.15 11.49 12.78

[0068] As can be seen from Table 1, the present invention uses InN nanopillars as the interface layer of solar cells to enhance the light absorption of solar cells and improve the photoelectric conversion efficiency of solar cells.

[0069] This invention uses InN nanopillars as the interface layer of a solar cell. Many publications emphasize growing nanopillars on GaAs and using InN as a hole transport layer to form a heterojunction, but its use as a passivation layer at the cell interface has not yet been reported. Currently, common two-dimensional materials, oxides, self-assembled molecular layers, and compound thin films are more commonly used as passivation layers, which lack micro / nano structures. Furthermore, this invention uses semiconductor narrow-bandgap InN nanopillars, which can effectively broaden the spectral response range of GaAs solar cells.

[0070] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A broadband-response GaAs heterojunction solar cell based on InN nanopillar interface modulation, characterized in that: From bottom to top, it includes a back electrode, an InGaP back field layer, a GaAs substrate layer, an InN nanopillar layer, a hole transport layer, a front electrode, and an anti-reflection ARC layer; the front electrode is disposed at both ends of the hole transport layer, and the anti-reflection ARC layer is disposed on the hole transport layer that is not covered by the front electrode. The InGaP back field layer is n-type, and the Si doping concentration is (1~3)×10⁻⁶. 17 / cm 3 ; The GaAs substrate is an n-type GaAs substrate with a Si doping concentration of (1~3)×10⁻⁶. 18 / cm 3 The crystal plane is (110); InN nanopillars serve as the interface layer for GaAs heterojunction solar cells. The hole transport layer is made of one or more of the following materials: graphene, Mxene, carbon nanotubes, and carbon quantum dots. The InN nanopillar layer was prepared by the following method: an InGaP back field layer / GaAs substrate was placed in an MBE growth chamber, the temperature of the In source and Ga source was increased, and the Ga source was introduced into the growth chamber to pre-deposit a Ga layer on the GaAs substrate; the Ga source was turned off, and the In source and N source were introduced into the growth chamber to grow InN nanopillars on the GaAs substrate.

2. The broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to claim 1, characterized in that: The growth conditions of the InN nanopillars are as follows: the temperature of the In source is 780℃~820℃, the growth temperature of the InN nanopillars is 350℃~450℃, the plasma source power is 200W~400W, the N2 flux is 0.7~2sccm, and the growth time is 1~3h. The temperature of the Ga source is 850℃~900℃, and the deposition time of the Ga source is 1~5min; The hole transport layer is made of carbon nanotubes.

3. The broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to claim 1, characterized in that: The thickness of the InGaP back field layer is 30~60μm; The thickness of the GaAs substrate layer is 250~350μm; The height of the InN nanopillar layers is 50~200 nm, and the diameter is 20~80 nm. The thickness of the hole transport layer is 100~200nm; The back electrode is Au; the front electrode is Ag. The anti-reflective ARC layer is in contact with the front electrode.

4. The method for fabricating a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to any one of claims 1 to 3, characterized in that: Includes the following steps: 1) Place the InGaP back field layer / GaAs substrate into the MBE growth chamber, raise the temperature of the In source and Ga source, pre-deposit a Ga source layer on the GaAs substrate, and then grow and prepare InN nanopillars. 2) A back electrode is deposited on the back side of the InGaP back field layer / GaAs substrate, i.e., the InGaP back field layer, and then annealed to form an ohmic contact. 3) Fabrication of a hole transport layer on InN nanopillars; 4) A front electrode is deposited at both ends of the hole transport layer, and an anti-reflection ARC layer is deposited on the hole transport layer not covered by the front electrode to obtain a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation.

5. The method for fabricating a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to claim 4, characterized in that: The InGaP back field layer mentioned in step 1) is n-type with a thickness of 30~60μm and a Si doping concentration of (1~3)×10⁻⁶. 17 / cm 3 The GaAs substrate is an n-type GaAs substrate with a thickness of 250~350μm and a Si doping concentration of (1~3)×10⁻⁶. 18 / cm 3 The crystal plane is (110) crystal plane, the temperature of the Ga source is 850℃~900℃, the Ga source deposition time is 1~5min; the temperature of the substrate during Ga source deposition is 350℃~450℃; The preparation conditions of the InN nanopillars described in step 1) are as follows: growth temperature is 350℃~450℃, In source temperature is 780℃~820℃, plasma source power is 200W~400W, N2 flux is 0.7~2sccm; growth time is 1~3h, nanopillar height is 50~200 nm, and diameter is 20~80 nm.

6. The method for fabricating a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to claim 4, characterized in that: The back electrode mentioned in step 2) is an Au electrode with a thickness of 100~120nm, an annealing temperature of 300~330℃, and an annealing time of 15~30s.

7. The method for fabricating a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to claim 4, characterized in that: The hole transport layer described in step 3) is obtained by preparing a thin film through filtration or by wet transfer of materials, with a thickness of 100~200nm.

8. The method for fabricating a broadband response GaAs heterojunction solar cell based on InN nanopillar interface modulation according to claim 4, characterized in that: The front electrode mentioned in step 4) is an Ag electrode with a thickness of 100~120nm; the anti-reflective ARC layer is one or more of WO3, MgF2, and MoO3 thin films with a thickness of 10~30nm.

Images