A gaas heterojunction solar cell based on a multifunctional n-gqd composite film and a preparation method thereof

Abstract

The application provides a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film and a preparation method thereof. The solar cell comprises a GaAs substrate, and an N-GQD interface passivation layer and a doped N-GQD hole transport layer are sequentially arranged on the GaAs substrate. N-GQD is hydrothermally synthesized by using low-cost raw materials, and then an interface passivation layer of a heterojunction cell is prepared by simple spin coating. A hole transport layer film is prepared by using a suction filtration method, is transferred to the GaAs substrate, and finally, an N-GQD layer is spin coated on the surface to prepare a solar cell. The solar cell can effectively broaden the spectral response range of the GaAs solar cell, reduce the interface carrier recombination, and improve the efficiency.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor materials, in particular to a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film and a preparation method thereof. BACKGROUND

[0002] In recent years, GaAs (gallium arsenide) solar cells have been widely used in the field of aerospace batteries 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, GaAs has weak absorption in the ultraviolet region, resulting in a narrow spectral response range of GaAs heterojunction solar cells, which affects the photoelectric conversion efficiency, and the interface carrier recombination of GaAs heterojunction solar cells is serious.

[0003] Quantum dot materials have down-conversion characteristics and a function similar to a front surface field (FSF) layer in a solar cell, which can absorb ultraviolet light and emit visible light with a longer wavelength, inhibit the non-radiative recombination of carriers between device interfaces, and therefore have great potential to broaden the spectral response range of solar cells and enhance light absorption. For example, the preparation method of a quantum dot light conversion film capable of improving the photoelectric conversion efficiency of a silicon solar cell is mentioned in application No. 202310762199.0, which applies a quantum dot down-conversion film to a silicon solar cell to improve the conversion efficiency of the silicon solar cell. However, the quantum dot film is prepared by an ultrasonic atomization film system, which is high in cost and complex in process. SUMMARY

[0004] The application embodiment provides a preparation method of a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film to solve the problems in the related art. The technical scheme is as follows:

[0005] In a first aspect, the application embodiment provides a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film, which comprises a GaAs substrate, and an N-GQDs interface passivation layer and a doped N-GQDs hole transport layer are sequentially arranged on the GaAs substrate.

[0006] In an embodiment, a back electrode is further arranged on the back surface of the GaAs substrate; and an anti-reflection layer and a front electrode are sequentially arranged on the hole transport layer.

[0007] In an embodiment, the back electrode is an Au electrode, and the thickness of the Au electrode film is 100-120 nm.

[0008] In an embodiment, the material of the hole transport layer is one or more than two combinations of carbon nanotubes, Mxene, PEdot or graphene.

[0009] In an embodiment, the anti-reflective layer is one of WO3, MgF2, MoO3 thin film.

[0010] In an embodiment, the thickness of the anti-reflective layer is 10-30 nm.

[0011] In an embodiment, the thickness of the front electrode is 100-120 nm.

[0012] In an embodiment, the material of the front electrode is one or more than two combinations of silver, titanium, copper, nickel, platinum or indium tin oxide.

[0013] In a second aspect, the embodiments of the present application provide a preparation method of a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film, comprising the following steps:

[0014] Step S1, evaporating a back electrode on the back surface of GaAs, forming an ohmic contact after annealing, and spin-coating an N-GQDs solution on the front surface of the GaAs substrate and naturally drying;

[0015] Step S2, preparing a hole transport layer film by using a suction filtration method, transferring the hole transport layer film to the surface of GaAs, and spin-coating an N-GQDs solution on the surface of the hole transport layer and naturally drying;

[0016] Step S3, evaporating an anti-reflective layer and a front electrode on the heterojunction obtained in step S2, and preparing a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film.

[0017] In an embodiment, the N-GQDs solution is prepared by a method comprising the following steps:

[0018] The aqueous solution of urea and citric acid is subjected to hydrothermal reaction treatment, the reaction liquid is subjected to solid-liquid separation, the liquid phase is subjected to freeze-drying to obtain the powder of the N-GQDs, and the N-GQDs solution is obtained by dissolving in water.

[0019] In an embodiment, the mass ratio of urea to citric acid is (0.6-0.9):(0.5-1).

[0020] In an embodiment, the hydrothermal reaction conditions are as follows: reaction temperature 150-180℃, reaction time 12-24h.

[0021] In an embodiment, the solid-liquid separation process is as follows: first using filter paper to filter, then centrifuging the filtrate, and finally dialysis.

[0022] In an embodiment, the pore size of the filter paper is 0.05-0.1 μm.

[0023] In an embodiment, the centrifugal processing speed is 6000-10000 rpm, the centrifugal processing time is 20-40 min, and the dialysis time is 1-3 days.

[0024] In an embodiment, in step S1, the annealing temperature is 300-330℃, and the annealing time is 10-30 s.

[0025] In an embodiment, the concentration of the N-GQDs solution is 0.05-0.5 mg / ml.

[0026] In an embodiment, the spin coating speed of the N-GQDs is 3000-5000 rpm, and the time is 30-60 s.

[0027] In an embodiment, in step S2, the transfer method is to paste the filter film obtained by filtering the hole transport layer material on the front surface of GaAs for drying, and the drying temperature is 60-80℃.

[0028] In an embodiment, the concentration of the N-GQDs solution is 0.05-0.5 mg / ml; and the spin coating speed of the N-GQDs solution is 3000-5000 rpm, and the time is 30-60 s.

[0029] The above technical solution has at least the following advantages or beneficial effects:

[0030] The N-GQDs are used as the interface passivation and down-conversion multifunctional layer of the GaAs heterojunction solar cell, which can effectively broaden the spectral response range of the GaAs solar cell, reduce the interface carrier recombination, and improve the efficiency of the GaAs heterojunction solar cell.

[0031] The GaAs heterojunction solar cell based on the multifunctional N-GQD composite film of the application uses low-cost raw materials to hydrothermally synthesize N-GQDs, then prepares the interface passivation layer of the heterojunction cell by simple spin coating, uses the method of suction filtration to prepare the hole transport layer film, transfers to the GaAs substrate, and finally spin coats a layer of N-GQDs on the surface to prepare the solar cell. The preparation process is simple, has commercial application prospects, and can significantly improve the photoelectric conversion efficiency compared with the GaAs solar cell without using quantum dots.

[0032] The above summary is only for the purpose of the description and is not intended to limit in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features will be readily apparent to those skilled in the art by reference to the drawings and the following detailed description. Attached Figure Description

[0033] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0034] Figure 1 Example 1 shows the GaAs heterojunction solar cell structure based on a multifunctional N-GQD composite thin film; from bottom to top, the structure consists of a back Au electrode, a GaAs substrate, an N-GQDs interface passivation layer, a doped N-GQDs hole transport layer, an anti-reflection layer (ARC), and a front Ag electrode.

[0035] Figure 2 The UV-Vis absorption (UV-vis) and PL spectra of the N-GQDs obtained in Example 1 are shown below.

[0036] Figure 3 The XRD pattern of N-GQDs obtained in Example 1;

[0037] Figure 4 The infrared spectrum (IR) of N-GQDs obtained in Example 1;

[0038] Figure 5 XPS spectra of N-GQDs obtained in Example 1;

[0039] Figure 6 The TEM image of N-GQDs obtained in Example 1;

[0040] Figure 7 The reflectance spectra of the GaAs heterojunction solar cell based on the multifunctional N-GQD composite thin film in Example 1 and the comparative example are shown.

[0041] Figure 8 The PL spectra of the GaAs heterojunction solar cell based on the multifunctional N-GQD composite thin film in Example 1 and the comparative example are shown.

[0042] Figure 9 The image shows the IV curve test results of the GaAs heterojunction solar cell based on the multifunctional N-GQD composite thin film in Example 1 and the comparative example. Detailed Implementation

[0043] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0044] To overcome the problems of narrow spectral response range, serious interface carrier recombination and high cost of the GaAs solar cell, the embodiment of the application provides a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film, which comprises a GaAs substrate, wherein an N-GQD interface passivation layer and a doped N-GQD hole transport layer are sequentially arranged on the GaAs substrate.

[0045] N-GQD is short for N-doped Graphene Quantum Dots, and the N-GQD is used as an interface passivation and down-conversion multifunctional layer of the GaAs heterojunction solar cell. Due to the down-conversion and interface passivation functions of the quantum dots, the conversion efficiency of the solar cell is significantly improved.

[0046] In an embodiment, the N-GQD interface passivation layer is obtained by coating an N-GQD solution on the front surface of the GaAs substrate by spin coating and then naturally drying.

[0047] In an embodiment, the N-GQD solution is prepared by hydrothermal reaction of urea and citric acid. As an embodiment, an aqueous solution of urea and citric acid is subjected to hydrothermal reaction treatment, the reaction solution is subjected to solid-liquid separation, the liquid phase is subjected to freeze-drying to obtain N-GQD powder, and the N-GQD powder is dissolved in water to obtain the N-GQD solution.

[0048] In an embodiment, urea and citric acid are weighed and dissolved in deionized water for stirring. After dissolution, the solution is transferred to a high-pressure reaction kettle. The high-pressure reaction kettle is moved into an oven for reaction at a certain temperature. After the reaction is completed, the solution is taken out and filtered to remove the precipitate and leave the filtrate. The filtrate is centrifuged, and the supernatant is taken. The obtained supernatant is subjected to dialysis and freeze-drying to obtain N-GQD powder. Finally, the N-GQD powder is weighed and configured into a solution with a certain concentration.

[0049] In an embodiment, the mass ratio of urea to citric acid is (0.6-0.9):(0.5-1).

[0050] In an embodiment, the hydrothermal reaction conditions are as follows: reaction temperature 150-180℃, reaction time 12-24h.

[0051] In an embodiment, the solid-liquid separation process is as follows: first, filter paper is used for filtration, and then the filtrate is subjected to centrifugal treatment.

[0052] In an embodiment, the pore size of the filter paper is 0.05-0.1 μm.

[0053] In an embodiment, the centrifugal treatment is performed at a centrifugal speed of 6000-10000 rpm for 20-40 min, and the dialysis is performed for 1-3 days.

[0054] The N-GQD is prepared from low-cost, non-toxic and environmentally friendly raw materials urea and citric acid. The N-GQD can be prepared through a hydrothermal reaction, and the preparation process is simple. An interface passivation layer of the N-GQD can be obtained through simple spin coating.

[0055] In an embodiment, the N-GQD-doped hole transport layer is prepared by spin coating the N-GQD solution with the hole transport layer. In the embodiment, the concentration of the N-GQD solution is 0.05-0.5 mg / ml; the spin coating speed of the N-GQD solution is 3000-5000 rpm, and the time is 30-60 s.

[0056] In an embodiment, the material of the hole transport layer is one or a combination of two or more of carbon nanotubes, Mxene, PEdot or graphene.

[0057] In an embodiment, a back electrode is further provided on the back surface of the GaAs substrate; and an anti-reflection layer and a front electrode are sequentially provided on the hole transport layer.

[0058] In an embodiment, the back electrode is an Au electrode, and the film thickness of the Au electrode is 100-120 nm.

[0059] In an embodiment, the anti-reflection layer is one of WO3, MgF2 and MoO3 films.

[0060] In an embodiment, the front electrode has a thickness of 100-120 nm.

[0061] In an embodiment, the material of the front electrode is one or a combination of two or more of silver, titanium, copper, nickel, platinum and indium tin oxide.

[0062] The embodiment of the application provides a preparation method of a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film, which comprises the following steps:

[0063] In step S1, a back electrode is evaporated on the back surface of the GaAs, and an ohmic contact is formed after annealing; and an N-GQD solution is spin coated on the front surface of the GaAs substrate and naturally dried.

[0064] Step S2, a hole transport layer film is prepared by using filtration, and the hole transport layer film is transferred to the GaAs surface, and N-GQDs solution is spin-coated on the surface of the hole transport layer for natural air drying;

[0065] Step S3, an anti-reflection layer and a front electrode are evaporated on the heterojunction obtained in step S2, to prepare a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film.

[0066] In an embodiment, the N-GQDs solution is prepared by a method comprising the following steps:

[0067] The aqueous solution of urea and citric acid is subjected to hydrothermal reaction treatment, and after solid-liquid separation, the liquid phase is freeze-dried to obtain the powder of N-GQDs; and the N-GQDs solution is obtained by dissolving in water.

[0068] In an embodiment, the mass ratio of urea to citric acid is (0.6-0.9):(0.5-1). The urea and citric acid are dissolved in water to prepare an aqueous solution of urea and citric acid, wherein the mass-volume ratio of citric acid to water is (0.5-1) g:(15-25) ml. In this embodiment, the aqueous solution is stirred at room temperature for 5-10 min during preparation.

[0069] In an embodiment, the hydrothermal reaction conditions are as follows: reaction temperature 150-180℃, reaction time 12-24h.

[0070] In an embodiment, the solid-liquid separation process is as follows: first, filtration is performed using filter paper, and then the filtrate is subjected to centrifugal treatment and dialysis.

[0071] In an embodiment, the pore size of the filter paper is 0.05-0.1μm.

[0072] In an embodiment, the centrifugal treatment is performed at a centrifugal speed of 6000-10000rpm for 20-40min.

[0073] In an embodiment, in step S1, the annealing temperature is 300-330℃, and the annealing time is 10-30s.

[0074] In an embodiment, the concentration of the N-GQDs solution is 0.05-0.5mg / ml.

[0075] In an embodiment, the spin-coating of N-GQDs is performed at a speed of 3000-5000rpm for 30-60s.

[0076] In an embodiment, in step S2, the transfer method is to paste the filter film of the hole transport layer material obtained by filtration on the front surface of GaAs for drying, and the drying temperature is 60-80°C. The GaAs heterojunction solar cell can be quickly prepared by simple filtration and transfer.

[0077] In an embodiment, the concentration of the N-GQDs solution is 0.05-0.5 mg / ml; and the rotation speed of the spin-coated N-GQDs solution is 3000-5000 rpm, and the time is 30-60 s.

[0078] The following is further illustrated by specific examples.

[0079] Example 1

[0080] A GaAs heterojunction solar cell based on a multifunctional N-GQD composite film and a preparation method thereof, comprising the following steps:

[0081] 0.72 g of urea and 0.84 g of citric acid were weighed and added to 18 ml of deionized water for dissolution, the stirring time was 10 min, and the temperature was room temperature under the condition of transferring to a 50 ml hydrothermal reaction kettle;

[0082] The high-pressure reaction kettle was moved into a vacuum oven, the reaction temperature was 180°C, and the time was 24 h. After the reaction was completed, the solution was taken out, filtered with filter paper with a pore size of 0.1 μm, and the precipitate was removed to leave the filtrate;

[0083] The filtrate was centrifuged at 10000 rpm for 40 min, and the supernatant obtained was dialyzed for 3 days and freeze-dried for 72 h to obtain N-GQDs powder. The obtained N-GQDs powder was configured into an N-GQDs solution with a concentration of 0.1 mg / ml;

[0084] Au electrode was evaporated on the back surface of GaAs, the thickness of Au film was 120 nm, the annealing temperature was 330°C, the annealing time was 20 s to form ohmic contact, N-GQDs was coated on the GaAs substrate by spin coating, the rotation speed was 3000 rpm, and the time was 30 s. Then, the carbon nanotubes were prepared into a filter film by filtration and pasted on the front surface of GaAs for drying, and the drying temperature was 60°C. Then, 10 μl of N-GQDs solution was spin-coated on the surface of the hole transport layer for natural air drying;

[0085] Ag electrode and WO3 were evaporated on the front surface of the heterojunction, the thickness of WO3 was 30 nm, and the thickness of the electrode was 120 nm to prepare a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film, and the structure is as shown in Figure 1 .

[0086] Example 2

[0087] A GaAs heterojunction solar cell based on a multifunctional N-GQD composite film and a preparation method thereof, comprising the following steps:

[0088] 0.6 g of urea and 1 g of citric acid were weighed and dissolved in 15 ml of deionized water, the stirring time was 5 min, the temperature was room temperature, and the solution was transferred to a 50 ml hydrothermal reaction kettle;

[0089] The high-pressure reaction kettle was moved into a vacuum oven, the reaction temperature was 150°C, the time was 24h, and after the reaction was completed, the solution was taken out, filtered with filter paper with a pore size of 0.05 μm, and the precipitate was removed to leave the filtrate;

[0090] The filtrate was centrifuged at 8000 rpm for 20 min, the supernatant obtained was dialyzed and freeze-dried for 24 h to obtain the N-GQDs powder, and the obtained N-GQDs powder was configured into an N-GQDs solution with a concentration of 0.05 mg / ml;

[0091] Au electrodes were evaporated on the back of GaAs, the Au film thickness was 100 nm, the annealing temperature was 315°C, the annealing time was 10 s to form ohmic contact, N-GQDs were coated on the GaAs substrate by spin coating, the rotation speed was 5000 rpm, the time was 60 s, then carbon nanotubes were prepared into a filter membrane by suction filtration and pasted on the front of GaAs for drying, the drying temperature was 80°C, and 20 μl of N-GQDs solution was spin-coated on the surface of the hole transport layer for natural air drying.

[0092] Ni electrodes and WO3 were evaporated on the front of the heterojunction, the WO3 thickness was 20 nm, and the electrode thickness was 110 nm to prepare a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film.

[0093] Example 3

[0094] A GaAs heterojunction solar cell based on a multifunctional N-GQD composite film and a preparation method thereof, comprising the following steps:

[0095] 0.9 g of urea and 0.5 g of citric acid were weighed and dissolved in 20 ml of deionized water, the stirring time was 5 min, the temperature was room temperature, and the solution was transferred to a 50 ml hydrothermal reaction kettle;

[0096] The high-pressure reaction kettle was moved into a vacuum oven, the reaction temperature was 165°C, the time was 12h, and after the reaction was completed, the solution was taken out, filtered with filter paper with a pore size of 0.1 μm, and the precipitate was removed to leave the filtrate;

[0097] The filtrate was centrifuged at 6000 rpm for 30 min, and the supernatant obtained was freeze-dried for 36 h to obtain the N-GQDs powder. The N-GQDs powder obtained was configured into an N-GQDs solution with a concentration of 0.5 mg / ml;

[0098] Au electrode was evaporated on the back of GaAs, the thickness of Au film was 110 nm, the annealing temperature was 300 °C, the annealing time was 30 s to form ohmic contact, N-GQDs were coated on the GaAs substrate by spin coating, the rotation speed was 4000 rpm, the time was 45 s, then carbon nanotubes were prepared into a filter membrane by suction filtration and pasted on the front of GaAs for drying, the drying temperature was 70 °C, and then 5 μl of N-GQDs solution was dropped on the surface of the hole transport layer for natural air drying.

[0099] Cu electrode and MoO3 were evaporated on the front of the heterojunction, the thickness of MoO3 was 10 nm, the thickness of the electrode was 100 nm to prepare GaAs heterojunction solar cells based on multifunctional N-GQD composite films.

[0100] Comparative Example 1

[0101] Comparative Example 1 is different from Example 1 in that N-GQDs are not added as interface passivation and down-conversion functional layer, and a carbon nanotube dispersion liquid containing the same mass of carbon nanotubes is suction filtered to prepare a thin film, which is transferred to a GaAs substrate to prepare a carbon nanotube / GaAs heterojunction solar cell.

[0102] The N-GQDs prepared in the examples were subjected to ultraviolet-visible absorption detection, and the ultraviolet-visible absorption (Uv-vis) and PL spectrum are shown in Figure 2 ;

[0103] The N-GQDs prepared in the examples were subjected to X-ray diffraction detection, and the XRD spectrum is shown in Figure 3 ;

[0104] The N-GQDs prepared in the examples were subjected to infrared spectrum detection, and the infrared spectrum (IR) is shown in Figure 4 ;

[0105] The N-GQDs prepared in the examples were subjected to X-ray photoelectron spectroscopy detection, and the XPS spectrum is shown in Figure 5 ;

[0106] The N-GQDs prepared in the examples were subjected to transmission electron microscope detection, and the TEM spectrum is shown in Figure 6 ;

[0107] The reflectivity curves of the solar cells prepared in the examples and the solar cells prepared in the comparative examples are shown in Figure 7As shown;

[0108] The PL curves of the solar cells prepared in the examples and the solar cells prepared in the comparative examples are as follows: Figure 8 As shown;

[0109] from Figures 2-6 It can be seen that N-GOD was prepared in this application. The final average particle size of N-GQD is 3-5 nm, with uniform particle size distribution and good dispersibility, indicating good quality. Its introduction into GaAs solar cells... Figures 7-8 It can be seen that the reflectance spectrum after introducing N-GQDs shows ( Figure 7 Its reflectivity is significantly reduced, which means that more solar energy spectrum is absorbed, and it exhibits lower reflectivity in the ultraviolet band, confirming the characteristic of N-GQDs to absorb ultraviolet light. This is demonstrated by the PL spectra of the examples and comparative examples. Figure 8 As can be seen, the strong PL peak in the comparative example indicates severe carrier recombination in GaAs solar cells. After inserting N-GQDs, the PL emission energy is highly quenched, indicating that N-GQDs have a good passivation effect. In the embodiments of this application, N-GQDs have been prepared using urea and citric acid, which can effectively broaden the spectral response range of GaAs solar cells, reduce interfacial carrier recombination, and improve the efficiency of solar cells.

[0110] Table 1 shows a comparison of the device parameters of the solar cell prepared in Example 1 and the solar cell prepared in Comparative Example 1. The IV curve of the solar cell in Example 1 is shown in the figure. Figure 9 As shown;

[0111] Table 1 Solar Cell Device Parameters

[0112] Parameter / sample Example 1 Comparative Example 1 J sc (mA / cm 2 )]]> 29.8 23.01 PCE (%) 16.53 11.75

[0113] From Table 1 and Figure 9 It can be seen that the short-circuit current density J of the solar cell in Embodiment 1 of this application sc It reached 29.8 mA / cm 2 In contrast, without the addition of N-GQD as an interface passivation and down-conversion functional layer, the short-circuit current density J of the solar cell in Comparative Example 1 was significantly lower. sc Only 23.01 mA / cm 2 From the perspective of power conversion efficiency (PCE), the PCE of the solar cell in Example 1 of this application reaches 16.53%, while the PCE of the solar cell in Comparative Example 1 is only 11.75%. This indicates that the solar cell in Comparative Example 1 has a narrow spectral response range, severe carrier recombination, and lower solar cell conversion efficiency compared to the GaAs heterojunction solar cell obtained by the preparation method of this application.

[0114] In summary, the application provides a GaAs heterojunction solar cell based on a multifunctional N-GQD composite film and a preparation method thereof. N-GQDs are hydrothermally synthesized from low-cost raw materials, and then a simple spin coating is used to prepare an interface passivation layer of the heterojunction solar cell. A hole transport layer film is prepared by the method of suction filtration, transferred to a GaAs substrate, and finally a layer of N-GQDs is spin-coated on the surface to prepare a solar cell. This can effectively broaden the spectral response range of the GaAs solar cell, reduce the interface carrier recombination, and improve the efficiency.

[0115] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0116] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0117] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film, characterized in that, The substrate includes a GaAs substrate, on which an N-GQDs interface passivation layer and a doped N-GQDs hole transport layer are sequentially disposed, and an anti-reflection layer and a front electrode are sequentially disposed on the hole transport layer; and a back electrode on the back side of the GaAs substrate. The hole transport layer is made of one or more of carbon nanotubes, Mxene, PEdot, or graphene; the antireflective layer is one of WO3, MgF2, or MoO3 thin films. Preparation methods include: Step S1: A back electrode is deposited on the back side of GaAs by vapor deposition, and an ohmic contact is formed after annealing. A layer of N-GQDs solution is spin-coated on the front side of the GaAs substrate and allowed to dry naturally. Step S2: Prepare a hole transport layer film by vacuum filtration, transfer the hole transport layer film to the GaAs surface, spin-coat the surface of the hole transport layer with N-GQDs solution and allow it to air dry. Step S3: An anti-reflection layer and a front electrode are deposited on the front side of the heterojunction obtained in step S2 to prepare a GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film. The N-GQDs solution is prepared by a method comprising the following steps: The aqueous solutions of urea and citric acid are subjected to hydrothermal reaction treatment. After solid-liquid separation, the liquid phase is freeze-dried to obtain the N-GQDs powder. The N-GQDs solution is obtained by dissolving the liquid phase in water.

2. The GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film according to claim 1, characterized in that, The back electrode is an Au electrode, and the thickness of the Au electrode film is 100~120nm.

3. A GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film according to claim 2, characterized in that, The front electrode has a thickness of 100~120nm; the material of the front electrode is one or a combination of two or more of silver, titanium, copper, nickel, platinum or indium tin oxide.

4. A GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film according to claim 1, characterized in that, The mass ratio of urea to citric acid is (0.6-0.9):(0.5-1). The conditions for the hydrothermal reaction are: reaction temperature 150~180℃, reaction time 12~24h.

5. A GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film according to claim 1, characterized in that, The solid-liquid separation process is as follows: first, filter with filter paper, then centrifuge the filtrate, and finally dialyze; the pore size of the filter paper is 0.05~0.1μm; the centrifugation speed is 6000~10000rpm, the centrifugation time is 20~40min; the dialysis time is 1~3 days.

6. A GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film according to claim 1, characterized in that, In step S1: the annealing temperature is 300~330℃, and the annealing time is 10~30s; The concentration of the N-GQDs solution is 0.05~0.5 mg / ml; the spin coating speed of the N-GQDs is 3000~5000 rpm, and the time is 30~60 s.

7. A GaAs heterojunction solar cell based on a multifunctional N-GQD composite thin film according to claim 1, characterized in that, In step S2: the method of transferring the hole transport layer film to the GaAs surface is to attach the filter membrane obtained by filtering the hole transport layer material to the front side of GaAs and dry it at a drying temperature of 60~80℃. The concentration of the N-GQDs solution is 0.05~0.5 mg / ml; the spin coating speed of the N-GQDs solution is 3000~5000 rpm, and the time is 30-60 s.

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