GaAs heterojunction solar cell and preparation method thereof

Abstract

The application discloses a GaAs heterojunction solar cell and a preparation method thereof. The GaAs heterojunction solar cell comprises a back electrode layer, a GaAs substrate, a first cuprous iodide layer, a carbon nanotube layer, a second cuprous iodide layer and a top electrode layer which are sequentially stacked. The preparation method of the GaAs heterojunction solar cell comprises the following steps: 1) preparing the back electrode layer; 2) preparing the first cuprous iodide layer; 3) preparing the carbon nanotube layer; 4) preparing the second cuprous iodide layer; and 5) preparing the top electrode layer. The GaAs heterojunction solar cell has the advantages of high photoelectric conversion efficiency, good stability and the like, and the preparation process is simple, the cost is low, and the GaAs heterojunction solar cell is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a GaAs heterojunction solar cell and a preparation method thereof. Background Art

[0002] Solar cells are semiconductor components that can efficiently absorb solar energy and convert it into electrical energy. CNTs / GaAs heterojunction solar cells are a new type of solar cell that have been widely used in recent years. CNTs / GaAs heterojunction solar cells use a GaAs substrate (bandgap of 1.42 eV) instead of a traditional Si substrate. They also employ a carbon nanotube (CNT) film with high light transmittance, high carrier mobility, and adjustable bandgap matching to form a heterojunction with the GaAs substrate. However, existing CNTs / GaAs heterojunction solar cells suffer from low photoelectric conversion efficiency, poor stability (device efficiency drops by half within a week), and complex manufacturing processes, making them difficult to fully meet the requirements of practical applications.

[0003] Therefore, it is of great significance to develop a GaAs heterojunction solar cell with high photoelectric conversion efficiency, good stability and simple preparation process. Summary of the Invention

[0004] The object of the present invention is to provide a GaAs heterojunction solar cell and a preparation method thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A GaAs heterojunction solar cell comprises a back electrode layer, a GaAs substrate, a first cuprous iodide layer, a carbon nanotube layer, a second cuprous iodide layer and a top electrode layer which are stacked in sequence.

[0007] Preferably, the back electrode layer is an Au layer.

[0008] Preferably, the thickness of the back electrode layer is 50 nm to 200 nm.

[0009] Preferably, the GaAs substrate is a Si-doped GaAs substrate, and the Si doping concentration is 1.0×10 18 / cm 3 ~2.5×10 18 / cm 3 .

[0010] Note: Doping concentration refers to per 1cm 3 The number of doping atoms contained in the material, for example, the doping concentration of Si is 1.0×10 18 / cm 3 Indicates every 1cm 3The Si-doped GaAs substrate contains 1.0×10 18 Si atoms.

[0011] Preferably, the thickness of the GaAs substrate is 100 μm to 500 μm.

[0012] Preferably, the thickness of the first cuprous iodide layer is 50 nm to 300 nm.

[0013] Preferably, the carbon nanotubes in the carbon nanotube layer have a length of 5 μm to 30 μm and a diameter (outer diameter) of 1 nm to 2 nm.

[0014] Preferably, the thickness of the second cuprous iodide layer is 50 nm to 300 nm.

[0015] Preferably, the top electrode layer is made of conductive silver paste.

[0016] Preferably, the thickness of the top electrode layer is 0.1 μm to 2.0 μm.

[0017] A method for preparing the GaAs heterojunction solar cell as described above comprises the following steps:

[0018] 1) Electron beam evaporation is used to deposit electrode metal on one side of the GaAs substrate, followed by annealing to form a back electrode layer;

[0019] 2) Spin coating the CuI dispersion on the side of the GaAs substrate where the back electrode layer is not deposited, and then annealing to form a first cuprous iodide layer;

[0020] 3) filtering the carbon nanotube dispersion to form a film, and then covering the obtained carbon nanotube film on the surface of the first cuprous iodide layer by pressing and laminating to form a carbon nanotube layer;

[0021] 4) Spin coating the CuI dispersion on the surface of the carbon nanotube layer, and then annealing to form a second cuprous iodide layer;

[0022] 5) Coating a conductive silver paste on the surface of the second cuprous iodide layer and drying it to form a top electrode layer, thereby obtaining a GaAs heterojunction solar cell.

[0023] Preferably, the annealing in step 1) is performed at a temperature of 300° C. to 400° C., and the annealing time is 20s to 40s.

[0024] Preferably, the concentration of the CuI dispersion in step 2) is 5 mg / mL to 20 mg / mL.

[0025] Preferably, the equipment used in the spin coating method in step 2) is a spin coater.

[0026] Preferably, the coating in step 2) is carried out at a spin coating machine speed of 3000 r / min to 6000 r / min, and the spin coating time is 30s to 60s.

[0027] Preferably, the annealing in step 2) is performed at a temperature of 80° C. to 105° C., and the annealing time is 10 min to 30 min.

[0028] Preferably, the carbon nanotube dispersion in step 3) contains an anionic surfactant.

[0029] Preferably, the anionic surfactant is sodium dodecylbenzenesulfonate.

[0030] Preferably, the concentration of the CuI dispersion in step 4) is 5 mg / mL to 20 mg / mL.

[0031] Preferably, the equipment used in the spin coating method in step 4) is a spin coater.

[0032] Preferably, the coating in step 4) is carried out under the condition that the rotation speed of the spin coater is 3000 r / min to 6000 r / min, and the spin coating time is 30s to 60s.

[0033] Preferably, the annealing in step 4) is performed at a temperature of 80° C. to 105° C., and the annealing time is 10 min to 30 min.

[0034] The principle of the present invention is that a heterojunction can be formed between n-type GaAs and p-type CuI in the GaAs heterojunction solar cell of the present invention. The GaAs substrate is excited by light to generate electron-hole pairs. The holes pass through a sandwich structure layer consisting of a first cuprous iodide layer, a carbon nanotube layer, and a second cuprous iodide layer and flow to an external circuit. At the same time, a high potential barrier exists between CuI and GaAs. The first cuprous iodide layer can hinder the flow of electrons to the carbon nanotube layer, which is beneficial for reducing surface recombination of carriers, thereby improving the performance of the solar cell. In addition, the second cuprous iodide layer can reduce interface loss existing in traditional electrode preparation processes and can serve as an anti-reflection layer to improve light utilization, thereby improving the performance and stability of the device.

[0035] The beneficial effects of the present invention are: the GaAs heterojunction solar cell of the present invention has the advantages of high photoelectric conversion efficiency, good stability, etc., and its preparation process is simple and the cost is low, and it is suitable for large-scale industrial application.

[0036] Specifically:

[0037] 1) The GaAs heterojunction solar cell of the present invention is provided with a sandwich structure layer consisting of a first cuprous iodide layer, a carbon nanotube layer, and a second cuprous iodide layer. The potential barrier between the first cuprous iodide layer and the GaAs substrate can block the flow of electrons to the carbon nanotube layer. The second cuprous iodide layer is used as a passivation layer to reduce interface losses, thereby reducing carrier recombination and increasing the open-circuit voltage, ultimately achieving improved photoelectric conversion efficiency and stability of the solar cell.

[0038] 2) The present invention prepares CuI thin films by spin coating, which can effectively avoid the problem of uneven component distribution that is easily caused by the traditional thermal evaporation method for preparing CuI thin films. The spin coating method is simple and easy to operate, which can greatly reduce the production cost of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the structure of the GaAs heterojunction solar cell of the present invention.

[0040] Description of the accompanying drawings: 10, back electrode layer; 20, GaAs substrate; 30, first cuprous iodide layer; 40, carbon nanotube layer; 50, second cuprous iodide layer; 60, top electrode layer.

[0041] Figure 2 Schematic diagram of the energy band structure of the GaAs heterojunction solar cell of Example 1.

[0042] Figure 3 Graph showing the stability test results of the GaAs heterojunction solar cells of Example 1 and the comparative example.

[0043] Figure 4 The current density-voltage relationship curves of the GaAs heterojunction solar cells of Examples 1 to 3 and the comparative example are shown. DETAILED DESCRIPTION

[0044] The present invention will be further explained and illustrated below with reference to specific embodiments.

[0045] Example 1:

[0046] A GaAs heterojunction solar cell (schematic diagram as shown Figure 1 As shown, the cross-sectional structure; the energy band structure diagram is as follows Figure 2 As shown), it consists of a back electrode layer 10, a GaAs substrate 20, a first cuprous iodide layer 30, a carbon nanotube layer 40, a second cuprous iodide layer 50 and a top electrode layer 60 stacked in sequence.

[0047] The preparation method of the above-mentioned GaAs heterojunction solar cell is as follows:

[0048] 1) Using electron beam evaporation system, a GaAs substrate with a thickness of 350 μm (Si-doped GaAs substrate with a Si doping concentration of 2.0×10 18 / cm 3 ) was deposited on one side of the substrate with a thickness of 120 nm, and then annealed at 330° C. for 30 seconds to form a back electrode layer;

[0049] 2) The GaAs substrate containing the back electrode layer obtained in step 1) was cracked into substrate pieces of 0.7 cm × 0.7 cm using a diamond pen, and then soaked in a 10% HCl solution for 3 minutes, and then ultrasonically cleaned with acetone, ethanol, and deionized water for 5 minutes each, and then dried with nitrogen. CuI powder was dissolved in acetonitrile to prepare a CuI dispersion with a concentration of 10 mg / mL. The CuI dispersion was then spin-coated on the side of the GaAs substrate not deposited with the back electrode layer. The spin coating was performed at a spin coater speed of 5000 r / min for 45 seconds, and then annealed at 95° C. for 20 minutes to form a first cuprous iodide layer.

[0050] 3) 1 mg of carbon nanotubes (5 μm to 30 μm in length and 1 nm to 2 nm in diameter) was added to a 0.5% by mass aqueous solution of sodium dodecylbenzenesulfonate, followed by ultrasonic dispersion. The mixture was then centrifuged at 4000 rpm for 20 min. 1.5 mL of the suspension was diluted to 30 mL with water to obtain a carbon nanotube dispersion with a concentration of 0.006 mg / mL. The mixture was then vacuum filtered to form a film. The resulting carbon nanotube film was then coated on the surface of the first cuprous iodide layer on the substrate sheet. Ethanol was then dripped on the film and pressed with fingers to ensure close contact between the carbon nanotube film and the substrate surface. The film was then dried in an oven at 55°C, and the filter membrane was removed to form a carbon nanotube layer.

[0051] 4) dissolving CuI powder in acetonitrile to prepare a CuI dispersion with a concentration of 5 mg / mL, and then spin-coating the CuI dispersion on the surface of the carbon nanotube layer at a spin coater speed of 5000 r / min for 45 seconds. The coating was then annealed at 85°C for 20 minutes to form a second cuprous iodide layer.

[0052] 5) Attach insulating tape to the edges of the second cuprous iodide layer (to reduce leakage), then apply a circle of conductive silver paste along the insulating tape, ensuring that the conductive silver paste is in contact with the second cuprous iodide layer. Then, place the film in an oven at 100°C for 30 minutes to form a top electrode layer, thus obtaining a GaAs heterojunction solar cell.

[0053] Performance testing:

[0054] The stability test results of the GaAs heterojunction solar cell of this embodiment (test period is 1 month) are as follows: Figure 3 As shown in the figure, the current density-voltage relationship curve is as follows Figure 4 shown.

[0055] Depend on Figure 3 and Figure 4 It can be seen that the open circuit voltage V of the GaAs heterojunction solar cell of this embodiment is oc is 0.58V, the short-circuit current density I SC 11.63 mA / cm 2 , the filling factor FF is 57.86%, the photoelectric conversion efficiency is 4.49%, and after 1 month of testing, the photoelectric conversion efficiency after attenuation is 91.3% of the initial value.

[0056] Example 2:

[0057] A GaAs heterojunction solar cell is prepared in the same manner as in Example 1, except that the following steps in step 2) are adjusted from "dissolving CuI powder in acetonitrile to prepare a CuI dispersion with a concentration of 10 mg / mL, spin-coating the CuI dispersion on the side of the GaAs substrate on which the back electrode layer is not deposited, performing the spin coating at a spin coater speed of 5000 r / min for 45 seconds, and annealing at 95°C for 20 minutes" to "dissolving CuI powder in acetonitrile to prepare a CuI dispersion with a concentration of 15 mg / mL, spin-coating the CuI dispersion on the side of the GaAs substrate on which the back electrode layer is not deposited, performing the spin coating at a spin coater speed of 6000 r / min for 60 seconds, and annealing at 85°C for 30 minutes."

[0058] Performance testing:

[0059] The current density-voltage relationship curve of the GaAs heterojunction solar cell of this embodiment is as follows: Figure 4 shown.

[0060] Depend on Figure 4 It can be seen that the open circuit voltage V of the GaAs heterojunction solar cell of this embodiment is oc is 0.56V, the short-circuit current density I SC 9.80mA / cm 2 , the filling factor FF is 58.35% and the photoelectric conversion efficiency is 3.69%.

[0061] Example 3:

[0062] A GaAs heterojunction solar cell is prepared in the same manner as in Example 1, except that the steps of "dissolving CuI powder in acetonitrile to prepare a CuI dispersion with a concentration of 5 mg / mL, and then spin-coating the CuI dispersion on the surface of a carbon nanotube layer at a spin coater speed of 5000 r / min for 45 seconds" in step 4) are adjusted to "dissolving CuI powder in acetonitrile to prepare a CuI dispersion with a concentration of 10 mg / mL, and then spin-coating the CuI dispersion on the surface of the carbon nanotube layer at a spin coater speed of 4000 r / min for 60 seconds."

[0063] Performance testing:

[0064] The current density-voltage relationship curve of the GaAs heterojunction solar cell of this embodiment is as follows: Figure 4 shown.

[0065] Depend on Figure 4 It can be seen that the open circuit voltage V of the GaAs heterojunction solar cell of this embodiment is oc is 0.55V, the short-circuit current density I SC 10.28 mA / cm 2 , the filling factor FF is 61.68% and the photoelectric conversion efficiency is 4.01%.

[0066] Comparative Example:

[0067] A GaAs heterojunction solar cell is identical to that of Example 1 except that the first cuprous iodide layer 30 and the second cuprous iodide layer 50 are not provided.

[0068] Performance testing:

[0069] The stability test results of the GaAs heterojunction solar cell of this comparative example (test period is 1 month) are as follows Figure 3 As shown in the figure, the current density-voltage relationship curve is as follows Figure 4 shown.

[0070] Depend on Figure 3 and Figure 4 It can be seen that the open circuit voltage V oc is 0.50V, the short-circuit current density I SC 6.67 mA / cm 2 The fill factor FF is 49.73%, and the photoelectric conversion efficiency is 1.66%. After one month of testing, the photoelectric conversion efficiency after attenuation is only 12.6% of the initial value.

[0071] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A GaAs heterojunction solar cell, characterized in that: The composition includes a back electrode layer, a GaAs substrate, a first cuprous iodide layer, a carbon nanotube layer, a second cuprous iodide layer and a top electrode layer stacked in sequence; the GaAs substrate is a Si-doped GaAs substrate with a Si doping concentration of 1.0×10 18 / cm 3 ~2.5×10 18 / cm 3 ; The thickness of the GaAs substrate is 100μm to 500μm; the thickness of the first cuprous iodide layer is 50nm to 300nm; the thickness of the second cuprous iodide layer is 50nm to 300nm; the length of the carbon nanotubes in the carbon nanotube layer is 5μm to 30μm, and the diameter is 1nm to 2nm.

2. The GaAs heterojunction solar cell according to claim 1, characterized in that: The back electrode layer is an Au layer; the thickness of the back electrode layer is 50nm to 200nm.

3. The GaAs heterojunction solar cell according to claim 1 or 2, characterized in that: The top electrode layer is made of conductive silver paste; the thickness of the top electrode layer is 0.1 μm to 2.0 μm.

4. A method for preparing a GaAs heterojunction solar cell according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Electron beam evaporation is used to deposit electrode metal on one side of the GaAs substrate, followed by annealing to form a back electrode layer; 2) Spin-coating the CuI dispersion onto the side of the GaAs substrate where the back electrode layer is not deposited, followed by annealing to form a first cuprous iodide layer; 3) filtering the carbon nanotube dispersion to form a film, and then covering the obtained carbon nanotube film on the surface of the first cuprous iodide layer and pressing and laminating it to form a carbon nanotube layer; 4) Spin coating the CuI dispersion onto the surface of the carbon nanotube layer, followed by annealing to form a second cuprous iodide layer; 5) Coating a conductive silver paste on the surface of the second cuprous iodide layer and drying it to form a top electrode layer to obtain a GaAs heterojunction solar cell.

5. The preparation method according to claim 4, characterized in that: Step 2) The concentration of the CuI dispersion is 5 mg / mL to 20 mg / mL; Step 4) The concentration of the CuI dispersion is 5 mg / mL to 20 mg / mL.

6. The preparation method according to claim 4 or 5, characterized in that: The annealing in step 1) is carried out at a temperature of 300°C to 400°C for 20s to 40s; the annealing in step 2) is carried out at a temperature of 80°C to 105°C for 10min to 30min; the annealing in step 4) is carried out at a temperature of 80°C to 105°C for 10min to 30min.

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