A GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer and a preparation method thereof

Abstract

The present invention belongs to the technical field of solar cell materials. To enhance the utilization of the solar spectrum and improve the photoelectric conversion efficiency of solar cells, a GaAs solar cell with a moth-eye micro-nanostructure anti-reflection layer and its preparation method are disclosed. The present invention utilizes MBE autocatalytic growth to grow a thin film with a nanopillar structure on a Si substrate with a SiO2 layer. PMMA is spin-coated on the surface of the thin film and then transferred to a GaAs and carbon nanotube heterojunction solar cell using a two-dimensional material wet transfer technique, thereby preparing a solar cell with a moth-eye micro-nanostructure anti-reflection layer. Compared with nanoimprint lithography and photolithography, the present invention is more convenient and environmentally friendly to operate, and does not require the use of hazardous gases or chemicals to etch the micro-nanostructure. The GaAs heterojunction solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer prepared using this method has no restrictions on the materials used in the anti-reflection layer, significantly improving the utilization of sunlight and thus significantly enhancing the photoelectric conversion efficiency of the device.

Description

Technical Field

[0001] The present invention belongs to the field of GaAs solar cells, and more specifically, relates to a GaAs solar cell with a moth-eye bionic micro-nano structure anti-reflection layer and a preparation method thereof. Background Art

[0002] In recent years, GaAs (Gallium Arsenide) solar cells have gained widespread application in the aerospace battery field due to their advantages, such as their direct band gap, excellent photoelectric conversion efficiency, and radiation resistance. According to the Shockley-Queisser model, the photoelectric conversion efficiency of single-junction GaAs solar cells can reach 30%. However, due to various limitations such as interface carrier recombination and surface photon loss, the efficiency of currently prepared GaAs solar cells still falls short of the theoretical value.

[0003] In order to improve the photoelectric conversion efficiency of GaAs solar cells, a common method is to reduce the optical reflection on the surface of the cell through optical management engineering, improve the absorption and utilization of sunlight, and thus improve the photoelectric conversion efficiency of the device. Currently, the commonly used methods to reduce surface photon loss are to use anti-reflection films and surface light-trapping micro-nano structures. Common surface light-trapping structures are mostly structures with different surface morphologies that mimic moth-eye bionics, such as nanopillars, nanocones, nanospheres, etc. This type of micro-nano structure is generally patterned by photolithography or nanoimprinting, which requires ICP (Inductively Coupled Plasma) or wet etching to prepare, requires the use of a large amount of harmful and hazardous liquids and gases, has high requirements for equipment, complex processes, and high costs.

[0004] Taking the production of micro-nano structures on the surface of GaAs solar cells as an example, Chinese patent application CN202111526602.7 discloses a GaAs nanocone Schottky junction solar cell and its preparation method, and mentions a method of using ICP equipment in combination with BCl3 gas and oxygen for etching to obtain GaAs nanocones. The operation of this scheme is relatively simple, but it requires the use of two dangerous gases, BCl3 and high-purity oxygen, and requires the assistance of ICP equipment, which is somewhat dangerous and directly leads to higher costs. Summary of the Invention

[0005] To overcome the problems of complex, high cost and high risk in preparing the above-mentioned surface micro-nanostructures, the present invention provides a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer and a preparation method thereof. The micro-nanostructure is grown by MBE and then transferred to a GaAs heterojunction solar cell by a two-dimensional material wet transfer method to obtain the required moth-eye bionic micro-nanostructure.

[0006] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0007] A GaAs solar cell with a moth-eye bionic micro-nano structure anti-reflection layer comprises a back electrode, a GaAs substrate, a hole transport layer, an anti-reflection layer and a front electrode from bottom to top; the anti-reflection layer is a nanocolumn film with a moth-eye bionic micro-nano structure.

[0008] Preferably, the nanopillars with moth-eye bionic micro-nanostructure are one or more of GaN, InGaN, and InN, the height of the nanopillars is 10-100 nm, the diameter is 20-60 nm, and the spacing between the nanopillars is 5-30 nm.

[0009] Preferably, the hole transport layer is a conductive and light-transmitting two-dimensional material, including one or more of graphene, Mxene, carbon nanotubes, TMDs, and PEDOT:PSS; the thickness of the hole transport layer is 80-120 nm.

[0010] Preferably, the GaAs substrate is an n-type GaAs substrate with a thickness of 250 to 350 μm and a Si doping concentration of (1 to 3)×10 18 / cm 3 , the crystal plane is (110) crystal plane.

[0011] Preferably, the back electrode is Au with a thickness of 100 to 120 nm; the front electrode is one or more of silver, titanium, copper, nickel, platinum, and indium tin oxide with a thickness of 100 to 120 nm.

[0012] A method for preparing a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer comprises the following steps:

[0013] Step 1: using an MBE device to autocatalytically grow moth-eye biomimetic micro-nanostructure nanopillars on a Si substrate with a SiO2 layer;

[0014] Step 2: Spin-coat a layer of PMMA on the surface of the nanopillars grown in step 1, dry it, and then place it in a dilute acid or dilute alkali to etch away the SiO2 layer for peeling;

[0015] Step 3: Clean the GaAs substrate and then transfer a two-dimensional material thin film onto it to obtain a GaAs / two-dimensional material heterojunction solar cell;

[0016] Step 4: Pick up the micro-nanostructure nanocolumn film peeled off in step 2 and cover it on the surface of the GaAs / two-dimensional material heterojunction solar cell in step 3, and dry it;

[0017] Step 5: Clean the battery in step 4 in acetone to remove PMMA.

[0018] Step six, evaporating a back electrode and a front electrode on the device obtained in step five, and finally obtaining a GaAs solar cell with a moth-eye bionic micro-nano structure anti-reflection layer.

[0019] Preferably, the nanocolumns with moth-eye biomimetic micro-nanostructures described in step 1 can be GaN, InGaN, InN, etc.

[0020] Preferably, the growth temperature of the micro-nanostructure nanocolumns grown by MBE in step 1 is 400° C. to 800° C., the radio frequency power of the N source is 300W to 400W, and the temperature of the Ga source and the In source is 800° C. to 900° C.

[0021] Further preferably, the growth temperature of the micro-nanostructure nanocolumns grown by MBE in step 1 is 750°C to 800°C, the N source RF power is 400W, and the Ga source and In source temperatures are 870°C to 900°C.

[0022] Preferably, the PMMA spin coating speed in step 2 is 1000-3000 rpm, the time is 10-30 s, the drying temperature is 80° C.-100° C., the time is 5-10 min, the acid or alkali concentration is 10%-15%, and the soaking time is 10-15 min.

[0023] Preferably, the two-dimensional material in step three includes all conductive and light-transmitting materials such as graphene, MXene, carbon nanotubes, TMDs, and PEDOT:PSS.

[0024] Preferably, the drying temperature in step 4 is 60° C. to 80° C., and the drying time is 5 to 10 minutes.

[0025] Preferably, the acetone soaking time in step five is 10 to 15 minutes.

[0026] Preferably, the acid or base in step 2 can be HF, KOH, NaOH, etc.

[0027] The MBE growth micro-nanostructure method used in the present invention can avoid the complex steps of photolithography and nanoimprinting, as well as the need to use hazardous gases and liquids to etch and form micro-nanostructures. The present invention can simply be transferred to a GaAs heterojunction solar cell through a wet process, avoiding damage to the solar cell caused by processes such as photolithography, nanoimprinting, and etching on the heterojunction solar cell. The moth-eye bionic micro-nanostructure preparation and heterojunction solar cell preparation processes are separated, effectively protecting the GaAs heterojunction solar cell. The GaAs heterojunction solar cell with a moth-eye bionic anti-reflection layer constructed in this way can not only reduce process risks, but also have better photoelectric conversion efficiency than a planar reflective layer, avoiding damage to the prepared heterojunction solar cell caused by the subsequent manufacture of the anti-reflection layer.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] Compared with the existing photolithography and nanoimprint etching methods, the solar cell with a moth-eye bionic micro-nano structure anti-reflection layer prepared by the present invention can also meet the use requirements in the device preparation process. Compared with the solar cell without the moth-eye bionic micro-nano structure anti-reflection layer, the photoelectric conversion efficiency is significantly improved. In addition, it can also avoid the dangers brought by the preparation process and the damage to the heterojunction solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of the GaAs / carbon nanotube heterojunction solar cell with a moth-eye bionic GaN micro-nanostructure anti-reflection layer obtained in Example 1, which includes, from bottom to top, a gold electrode, a GaAs substrate, a carbon nanotube film, a GaN nanocolumn, and a silver electrode.

[0031] Figure 2 This is a scanning electron microscope test image of the GaN nanocolumns with the moth-eye bionic micro-nanostructure anti-reflection layer obtained in Example 1.

[0032] Figure 3 The IV curves of the devices prepared in Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and specific examples, but the examples do not limit the present invention in any form.

[0034] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0035] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0036] Example 1

[0037] A method for preparing a GaAs solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer comprises the following steps:

[0038] Step 1: Use MBE equipment to autocatalytically grow GaN moth-eye biomimetic micro-nanostructure nanopillars on a Si substrate with a SiO2 layer. The nanopillars have a height of 50nm, a diameter of 40nm, and a spacing of 10nm between nanopillars. The growth temperature is 800℃, the Ga source temperature is 900℃, and the N source power is 400W.

[0039] Step 2: Spin-coat a layer of PMMA on the surface of the nanopillars grown in step 1 at a speed of 3000 rpm for 30 seconds, dry the nanopillars at 80°C for 10 minutes, and then place them in a 10% HF solution to remove the SiO2 layer.

[0040] Step 3: Transfer a 100 nm thick carbon nanotube film onto the cleaned GaAs substrate with a thickness of 350 μm to obtain a GaAs / carbon nanotube heterojunction solar cell;

[0041] Step 4: Pick up the GaN micro-nanostructure nanocolumn film peeled off in step 2 and cover it on the surface of the GaAs / carbon nanotube heterojunction solar cell prepared in step 3, and dry it at a drying temperature of 80° C. for 10 minutes.

[0042] Step 5: Wash the battery in step 5 in acetone to remove PMMA. The acetone time is 15 minutes to finally obtain a GaAs heterojunction solar cell with a moth-eye bionic micro-nano structure. The step further includes the following steps:

[0043] (1) Using electron beam evaporation, a 120 nm thick Au layer was deposited on the back side of the GaAs substrate (the side without micro-nanostructures) as the back electrode;

[0044] (2) annealing the Au electrode at 330°C in a nitrogen atmosphere for 30 seconds to form an ohmic contact;

[0045] (3) The carbon nanotube film transfer method in step 3 is to filter the carbon nanotube film on the surface of the GaAs substrate (the side with the micro-nano structure) using a PES (polyethersulfone) filter membrane and a carbon nanotube dispersion concentration of 0.05 mg / ml, and then transfer it to the GaAs substrate;

[0046] (4) A 120 nm thick silver layer is evaporated on the prepared film with the moth-eye bionic micro-nano structure anti-reflection layer as a surface electrode, thereby completing the preparation of the GaAs / carbon nanotube heterojunction solar cell with the moth-eye bionic micro-nano structure anti-reflection layer.

[0047] Example 2

[0048] A method for preparing a GaAs solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer comprises the following steps:

[0049] Step 1: Use MBE equipment to autocatalytically grow GaN moth-eye biomimetic micro-nanostructure nanopillars on a Si substrate with a SiO2 layer. The nanopillars have a height of 50nm, a diameter of 40nm, and a spacing of 10nm between nanopillars. The growth temperature is 750℃, the Ga source temperature is 870℃, and the N source power is 400W.

[0050] Step 2: Spin-coat a layer of PMMA on the surface of the nanopillars grown in step 1 at a speed of 1000 rpm for 15 seconds, dry the nanopillars at 60°C for 8 minutes, and place them in a 10% HF solution to remove the SiO2 layer.

[0051] Step 3: Transfer a 100 nm thick carbon nanotube film onto the cleaned GaAs substrate with a thickness of 350 μm to obtain a GaAs / carbon nanotube heterojunction solar cell;

[0052] Step 4: Pick up the GaN micro-nanostructure nanocolumn film peeled off in step 2 and cover it on the surface of the GaAs / carbon nanotube heterojunction solar cell prepared in step 3, and dry it at a drying temperature of 60° C. for 5 minutes.

[0053] Step 5: Wash the battery in step 5 in acetone to remove PMMA. The acetone time is 10 minutes to finally obtain a GaAs heterojunction solar cell with a moth-eye bionic micro-nano structure. The step further includes the following steps:

[0054] (1) Using electron beam evaporation, a 120 nm thick Au layer was deposited on the back side of the GaAs substrate (the side without micro-nanostructures) as the back electrode;

[0055] (2) annealing the Au electrode at 350 °C in a nitrogen atmosphere for 30 s to form an ohmic contact;

[0056] (3) The carbon nanotube film transfer method in step 3 is to filter the carbon nanotube film on the surface of the GaAs substrate (the side with the micro-nano structure) using a PES (polyethersulfone) filter membrane and a carbon nanotube dispersion concentration of 0.005 mg / ml, and then transfer it to the GaAs substrate;

[0057] (4) A 120 nm thick silver layer is evaporated on the prepared film with the moth-eye bionic micro-nano structure anti-reflection layer as a surface electrode, thereby completing the preparation of the GaAs / carbon nanotube heterojunction solar cell with the moth-eye bionic micro-nano structure anti-reflection layer.

[0058] Comparative Example 1

[0059] Different from Example 1, Comparative Example 1 is a GaAs / carbon nanotube heterojunction solar cell without a moth-eye bionic micro-nanostructure anti-reflection layer, and the other aspects are the same.

[0060] Table 1

[0061]

[0062]

[0063] The device parameter comparison of the solar cell prepared in Example 1 and the solar cell prepared in Comparative Example 1 is shown in Table 1. The IV curves of the solar cells of Example 1 and Comparative Example 1 are shown in Table 1. Figure 3 shown.

Claims

1. A method for preparing a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer, characterized in that: The following steps are involved: Step 1: using an MBE device to autocatalytically grow moth-eye biomimetic micro-nanostructure nanopillars on a Si substrate with a SiO2 layer; Step 2: Spin-coat a layer of PMMA on the surface of the nanopillars grown in step 1, dry it, and then place it in a dilute acid or dilute alkali to etch away the SiO2 layer for peeling; Step 3: transferring a layer of two-dimensional material thin film onto the cleaned GaAs substrate to obtain a GaAs / two-dimensional material heterojunction solar cell; Step 4: Pick up the micro-nanostructure nanocolumn film peeled off in step 2 and cover it on the surface of the GaAs / two-dimensional material heterojunction solar cell in step 3, and dry it; Step 5: Clean the battery in step 4 in acetone to remove PMMA. Step 6: Vapor-depositing a back electrode and a front electrode on the device obtained in step 5, thereby obtaining a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer; The GaAs solar cell comprises a back electrode, a GaAs substrate, a hole transport layer, an anti-reflection layer and a front electrode from bottom to top; the anti-reflection layer is a nanocolumn film with a moth-eye bionic micro-nano structure; The nanocolumns with moth-eye bionic micro-nanostructures are one or more of GaN, InGaN, and InN. The nanocolumns have a height of 10-100 nm, a diameter of 20-60 nm, and a spacing of 5-30 nm between the nanocolumns.

2. The method for preparing a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: In step 1, the growth temperature of the micro-nanostructure nanocolumns grown by MBE is 400°C~800°C, the N source RF power is 300W~400W, and the Ga source and In source temperatures are 800°C~900°C.

3. The method for preparing a GaAs solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: In step 2, the PMMA spin coating speed is 1000-3000 rpm, the time is 10-30 s, the drying temperature is 80° C.-100° C., the time is 5-10 min, the acid or base concentration is 10 wt %-15 wt %, and the immersion time is 10-15 min.

4. The method for preparing a GaAs solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: The drying temperature in step 4 is 60°C to 80°C, and the drying time is 5 to 10 minutes.

5. The method for preparing a GaAs solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: The acetone soaking time in step 5 is 10 to 15 minutes.

6. The method for preparing a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: The hole transport layer is a conductive and light-transmitting two-dimensional material, including one or more of graphene, Mxene, carbon nanotubes, TMDs, and PEDOT:PSS; the thickness of the hole transport layer is 80-120 nm.

7. The method for preparing a GaAs solar cell with a moth-eye biomimetic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: 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 18 / cm 3 , the crystal plane is (110) crystal plane.

8. The method for preparing a GaAs solar cell with a moth-eye bionic micro-nanostructure anti-reflection layer according to claim 1, characterized in that: The back electrode is Au with a thickness of 100-120 nm; the front electrode is one or more of silver, titanium, copper, nickel, platinum, and indium tin oxide with a thickness of 100-120 nm.

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