Wide-spectral-response GaAs heterojunction solar cell based on InN nanorod interface modulation and preparation of wide-spectral-response GaAs heterojunction solar cell

Abstract

The invention belongs to the technical field of solar cells, and discloses a wide-spectral-response GaAs heterojunction solar cell based on InN nanorod interface modulation and preparation of the wide-spectral-response GaAs heterojunction solar cell. The solar cell sequentially comprises a back electrode, an InGaP back field layer, a GaAs substrate layer, an InN nanorod layer, a hole transport layer, a front electrode and an anti-reflection ARC layer from bottom to top. And the InN nanorod is used as an interface layer of the GaAs heterojunction solar cell. The invention also discloses a preparation method of the solar cell. According to the GaAs heterojunction solar cell, the InN nanorods are used as the interface layer of the GaAs heterojunction solar cell, lattice mismatch can be relieved, and carrier recombination loss is reduced; meanwhile, through the synergistic effect of the micro-nano structure design and the narrow-band gap characteristic of the InN nanorod, the spectral response range is widened, the light absorption is enhanced, and the photoelectric conversion efficiency is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of GaAs solar cells, and particularly relates to a wide-spectrum-response GaAs heterojunction solar cell based on InN nanocolumn interface modulation and a preparation method thereof. BACKGROUND

[0002] In recent years, GaAs (Gallium Arsenide) solar cells have been widely applied due to their direct band gap, 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, the current GaAs solar cells still have a certain gap with the theoretical value due to various factors such as interface carrier recombination, narrow spectral absorption range, and weak light absorption.

[0003] In order to improve the photoelectric conversion efficiency of GaAs solar cells, the common method is to improve the absorption of sunlight and reduce the loss of carriers through optical and electrical management engineering, so as to improve the photoelectric conversion efficiency of the device. Therefore, the light trapping effect of micro-nano structures and the interface management engineering of solar cells have attracted widespread attention. CN202111526602.7 discloses a GaAs nanotaper Schottky junction solar cell and a preparation method thereof, which mentions a method of using an ICP device to etch GaAs nanotapers with BCl3 gas and oxygen. This scheme directly etches GaAs substrates, which can easily damage the GaAs substrates. The use of BCl3 and high-purity oxygen gases is dangerous, and although this scheme can enhance light absorption to some extent, it does not solve the problems of narrow spectral absorption range and interface carrier loss of GaAs solar cells. SUMMARY

[0004] In order to overcome the problems of GaAs heterojunction solar cell interface carrier recombination and narrow spectral absorption range in the prior art, the application provides a wide-spectrum-response GaAs heterojunction solar cell based on InN nanocolumn interface modulation and a preparation method thereof. In this application, InN nanocolumns are used as the interface modulation layer of GaAs heterojunction solar cells, which can effectively widen the spectral response range, enhance light absorption, and improve photoelectric conversion efficiency.

[0005] To solve the above technical problems, the technical scheme of the application is as follows:

[0006] A wide-spectrum-response GaAs heterojunction solar cell based on InN nanocolumn interface modulation, from bottom to top, comprises 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.

[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 17 / cm 3 .

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

[0010] The InN nanocolumn layer has a height of 50-200 nm and a diameter of 20-80 nm.

[0011] The InN nanocolumn serves as an interface layer of the GaAs heterojunction solar cell, and the front electrode is arranged at both ends of the hole transport layer.

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

[0013] The preparation method of the InN nanocolumn layer is as follows: the InGaP back field layer / GaAs substrate is placed in an MBE growth chamber, the temperature of the In source and the Ga source is raised, the Ga source enters the growth chamber to pre-deposit a layer of Ga source on the GaAs substrate; the Ga source is closed, and the In source and the N source enter the growth chamber to grow InN nanocolumns on the GaAs substrate.

[0014] The preparation method of the wide-spectrum response GaAs heterojunction solar cell based on InN nanocolumn interface modulation includes the following steps:

[0015] 1) The InGaP / GaAs substrate is placed in an MBE growth chamber, the temperature of the In source and the Ga source is raised, a layer of Ga source is pre-deposited on the GaAs substrate, and then InN nanocolumns are grown to form an InN nanocolumn layer;

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

[0017] 3) A hole transport layer is prepared on the front of the InN nanocolumn layer;

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

[0019] The InGaP back field layer in step 1) is n-type, with a thickness of 30-60 μm and a Si doping concentration of (1-3) x 10 17 / cm 3 The GaAs absorption layer is an n-type GaAs substrate, with a thickness of 250-350 μm and a Si doping concentration of (1-3) x 10 18 / cm 3 , and a crystal face of (110) crystal face. The temperature of the Ga source is 850-900 DEG C, and the deposition time of the Ga source into the growth chamber is 1-5 min, at which time the temperature of the substrate is 350-450 DEG C.

[0020] The growth temperature of the InN nanocolumn is 350-450 DEG C (the temperature of the In source is 780-820 DEG C, after deposition of the Ga source, the Ga source shutter is closed, the In source and the N source are opened for InN nanocolumn deposition, at which time the temperature of the substrate is 350-450 DEG C), the plasma source power is 200-400 W, and the N2 flux is 0.7-2 sccm; the growth time is 1-3 h, the nanocolumn height is 50-200 nm, and the diameter is 20-80 nm.

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

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

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

[0024] The present application grows InN nanocolumns on a GaAs substrate as an interface modulation layer of a GaAs heterojunction solar cell, which can relieve lattice mismatch and reduce carrier recombination loss; at the same time, through the synergistic effect of the micro-nano structure design and the narrow band gap characteristics of the InN nanocolumn, the spectral response range is widened, the light absorption is enhanced, and the photoelectric conversion efficiency is improved.

[0025] The InN nanocolumn layer of the present application is an interface between GaAs and a hole transport layer, and the micro-nano structure thereof helps to enhance light absorption, reduce reflection, passivate the interface, and reduce the recombination of carriers at the interface. Meanwhile, the InN nanocolumn has a narrow band gap, can widen the spectral absorption range, absorb infrared spectrum range, and enhance the effective utilization of sunlight. The transport efficiency of holes can be improved, and more hole carriers can reach the hole transport layer.

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

[0027] In a GaAs solar cell, the InN nanocolumn is grown as an interface modulation layer. The longitudinal growth mode of the InN nanocolumn can relieve lattice mismatch and reduce the loss of interface carriers. In addition, the band gap of InN is 0.7 eV, which can absorb near-infrared light (wavelength range that GaAs cannot respond to), widen the spectral response range of the solar cell, and the micro-nano light trapping effect of the InN nanocolumn can enhance light absorption. The InN nanocolumn is used as an interface modulation layer of a solar cell, and the synergistic effect of the micro-nano structure design and the narrow band gap characteristics can effectively improve the photoelectric conversion efficiency of the solar cell. BRIEF DESCRIPTION OF DRAWINGS

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

[0029] Figure 2 FIG. 2 is a cross-sectional SEM image of the InN nanocolumns grown on the GaAs substrate according to Example 1;

[0030] Figure 3 FIG. 3 is an I-V curve of the solar cell according to Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0031] The present application will be further described below in conjunction with the drawings and specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0032] A GaAs heterojunction solar cell based on InN nanocolumn interface modulation has a structure as shown in FIG. 1, which includes, from bottom to top, a back electrode 1, an InGaP back field layer 2, a GaAs substrate layer 3, an InN nanocolumn layer 4, a hole transport layer 5, a front electrode 6, and an anti-reflection ARC layer 7. Figure 1 A GaAs heterojunction solar cell based on InN nanocolumn interface modulation has a structure as shown in FIG. 1, which includes, from bottom to top, a back electrode 1, an InGaP back field layer 2, a GaAs substrate layer 3, an InN nanocolumn layer 4, a hole transport layer 5, a front electrode 6, and an anti-reflection ARC layer 7.

[0033] The InN nanocolumn layer is used as an interface layer of the GaAs heterojunction solar cell, and the front electrode is arranged at two ends of the hole transport layer.

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

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

[0036] The GaAs substrate layer is an n-type GaAs substrate, with a thickness of 250-350 μm, a Si doping concentration of (1-3) x 10 18 / cm 3 , and a crystal face of (110) crystal face.

[0037] The InN nanocolumn layer has 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 nanotube, and carbon quantum dot, and is preferably carbon nanotube.

[0039] The InN nanocolumn layer is used as an interface layer of the GaAs heterojunction solar cell, and the front electrode is arranged at two ends of the hole transport layer.

[0040] The preparation method of the InN nanocolumn layer is as follows: the InGaP back field layer / GaAs substrate is placed into an MBE growth chamber, the temperature of an In source and a Ga source is increased, the Ga source enters the growth chamber to pre-deposit a layer of Ga source on the GaAs substrate; the Ga source is closed, the In source and an N source enter the growth chamber to grow the InN nanocolumn 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-reflection layer ARC is one or more of WO3, MgF2, and MoO3 thin films, with a thickness of 10-30 nm.

[0042] Embodiment 1

[0043] A preparation method of a GaAs heterojunction solar cell based on InN nanocolumn interface modulation, comprising the following steps:

[0044] 1) An n-type InGaP / GaAs substrate is used, the thickness of the InGaP layer is 50 μm, the Si doping concentration is 1 x 10 17 / cm 3 , the thickness of the GaAs is 350 μm, and the Si doping concentration is 1 x 1018 / cm 3 , the crystal face is (110) crystal face, put into MBE growth chamber, raise the temperature of In source and Ga source, open Ga source shutter into the growth chamber, deposit a layer of Ga source on the substrate in advance, the temperature of Ga source is 850℃, the deposition time is 3min, the substrate temperature is 400℃; then close the Ga source shutter, open the In source and N source shutter, In source and N source enter the growth chamber to grow InN nanocolumn, the growth temperature is 400℃, the In source temperature is 800℃, the plasma source power is 400W, the N2 flux is 1sccm; the growth time is 2h, the nanocolumn height is 100nm, the diameter is 50nm;

[0045] 2) evaporate a layer of Au electrode on the back of InGaP / GaAs substrate and anneal to form ohmic contact, the thickness of Au electrode is 120nm, the annealing temperature is 330℃, the annealing time is 30s;

[0046] 3) prepare a layer of hole transport layer on the front of the InN nanocolumn growth, adopt the method of filtration to prepare carbon nanotube film, the thickness is 100nm;

[0047] 4) evaporate a layer of front Ag electrode and anti-reflection layer ARC on the hole transport layer, the thickness of Ag electrode is 100nm; the anti-reflection layer ARC is WO3, the thickness is 15nm, obtain a GaAs heterojunction solar cell based on InN nanocolumn interface modulation.

[0048] Figure 2 The cross-sectional SEM of InN nanocolumn grown on the GaAs substrate obtained in example 1.

[0049] Example 2

[0050] A preparation method of GaAs heterojunction solar cell based on InN nanocolumn interface modulation, comprising the following steps:

[0051] 1) n-type InGaP / GaAs substrate, the thickness of InGaP layer is 50μm, the Si doping concentration is 1×10 17 / cm 3 , the thickness of GaAs is 350μm, the Si doping concentration is 1×10 18 / cm 3, the crystal face is (110) crystal face, put into the MBE growth chamber, increase the temperature of In source and Ga source, open the Ga source shutter into the growth chamber, pre-deposited a layer of Ga source on the substrate, the temperature of Ga source is 900℃, the deposition time is 2min, the substrate temperature is 410℃; then close the Ga source shutter, open the In source and N source shutter, In source and N source enter the growth chamber to grow InN nanocolumn, the growth temperature is 410℃, the In source temperature is 800℃, the plasma source power is 400W, the N2 flux is 1.5sccm; the growth time is 1.5h, the nanocolumn height is 80nm, the diameter is 40nm;

[0052] 2) Evaporate a layer of Au electrode on the back of InGaP / GaAs substrate and anneal to form ohmic contact, the thickness of Au electrode is 120nm, the annealing temperature is 330℃, the annealing time is 30s;

[0053] 3) Prepare a layer of hole transport layer on the front of InN nanocolumn growth, prepare carbon nanotube film by filtration method, the thickness is 100nm;

[0054] 4) Evaporate a layer of front Ag electrode and anti-reflection layer ARC on the hole transport layer, the thickness of Ag electrode is 100nm; the anti-reflection layer ARC is MgF2, the thickness is 20nm, to obtain a wide spectrum response GaAs heterojunction solar cell based on InN nanocolumn interface modulation.

[0055] Comparative Example 1

[0056] 1) n-type InGaP / GaAs substrate, the thickness of InGaP layer is 50μm, the Si doping concentration is 1×10 17 / cm 3 , the thickness of GaAs is 350μm, the Si doping concentration is 1×10 18 / cm 3 , the crystal face is (110) crystal face;

[0057] 2) Evaporate a layer of Au electrode on the back of InGaP / GaAs substrate and anneal to form ohmic contact, the thickness of Au electrode is 120nm, the annealing temperature is 330℃, the annealing time is 30s;

[0058] 3) Prepare a layer of hole transport layer on the front, prepare carbon nanotube film by filtration method, the thickness is 100nm;

[0059] 4) Evaporate a layer of front Ag electrode and anti-reflection layer ARC on the hole transport layer, the thickness of Ag electrode is 100nm; the anti-reflection layer ARC is WO3, the thickness is 15nm, to obtain a solar cell.

[0060] Comparative Example 2

[0061] 1) n-type InGaP / GaAs substrate, the thickness of InGaP layer is 50 μm, the Si doping concentration is 1×10 17 / cm 3 , the thickness of GaAs is 350 μm, the Si doping concentration is 1×10 18 / cm 3 , and the crystal face is (110) crystal face;

[0062] 2) evaporating an Au electrode on the back of the InGaP / GaAs substrate and annealing to form an ohmic contact, the thickness of the Au electrode is 120 nm, the annealing temperature is 330℃, the annealing time is 30 s, and evaporating a 2 nm thick Al2O3 film on the front of the InGaP / GaAs substrate as an interface passivation layer;

[0063] 3) preparing a hole transport layer on the front with the Al2O3 film, and preparing a carbon nanotube film by the method of filtration film preparation, the thickness is 100 nm;

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

[0065] The solar cell prepared in Example 1 and the solar cell prepared in Comparative Examples 1 and 2 are compared in terms of device parameters as shown in Table 1, and the I-V curves of the solar cells of Example 1 and Comparative Examples 1 and 2 are shown in Figure 3 .

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

[0067] Parameter / sample Example 1 Comparative Example 1 Comparative Example 2 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] From Table 1, it can be seen that the InN nanocolumn as the interface layer of the solar cell enhances the light absorption of the solar cell and improves the photoelectric conversion efficiency of the solar cell.

[0069] The InN nanocolumn as the interface layer of the solar cell in the present application, many literatures more emphasize the growth of nanocolumns on GaAs, and InN is used as a hole transport layer to form a heterojunction, but it has not been reported as a passivation layer of the interface of the cell. At present, more common two-dimensional materials, oxides, self-assembled molecular layers, compound films, etc. are used as passivation layers, which do not have micro-nano structure, and the present application uses semiconductor narrow-bandgap InN nanocolumns, which can effectively broaden the spectral response range of the GaAs solar cell.

[0070] The application is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the application, those skilled in the art can make some replacements and modifications to some technical features without creative labor according to the disclosed technical content, and the replacements and modifications are all within the protection scope of the application.

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. InN nanopillar layers are prepared by the following method: 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 a Ga source layer is pre-deposited on the GaAs substrate by entering the growth chamber; 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.

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 30–60 μm; The thickness of the GaAs substrate layer is 250–350 μm; 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 100–200 nm; 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 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.

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 30–60 μm 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 250–350 μm 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 50~200nm, and diameter is 20~80nm.

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 100-120 nm, an annealing temperature of 300-330 °C, and an annealing time of 15-30 s.

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 vacuum filtration or by wet transfer of materials, with a thickness of 100-200 nm.

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 100-120 nm; the anti-reflective layer ARC is one or more of WO3, MgF2, and MoO3 thin films with a thickness of 10-30 nm.

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