A composite hole transport thin film / gallium arsenide heterojunction photoelectrode and preparation and application thereof

Abstract

The application belongs to the technical field of photoelectrochemistry, and discloses a composite hole transport thin film / gallium arsenide heterojunction photoelectrode and a preparation and application thereof. The photoelectrode comprises a back electrode, a gallium arsenide substrate and a composite hole transport thin film arranged in sequence from bottom to top. The preparation of the composite hole transport thin film comprises sequentially preparing a carbon nanotube thin film, a benzodipyrromethene film layer and a graphene oxide film layer on the gallium arsenide substrate. The carbon nanotube, the benzodipyrromethene and the graphene oxide are synergistically compounded, so that the carrier separation and transport capacity of the gallium arsenide heterojunction are effectively improved. The photoelectrode improves the photoelectric conversion efficiency, improves the chemical stability and improves the comprehensive performance of the device. The application further provides a preparation method of the photoelectrode. The method is simple and low in cost. The photoelectrode is used for a photovoltaic-photoelectrochemical integrated device, in particular, a photoelectrochemical water electrolysis hydrogen production.

Description

Technical Field

[0001] This invention belongs to the technical field of photoelectrochemistry, specifically relating to a composite hole transport thin film / gallium arsenide heterojunction photoelectrode, its preparation method, and its application. The photoelectrode is used in photovoltaic-photoelectrochemical integrated devices. Background Technology

[0002] With the increasing demand for sustainable energy, developing efficient photoelectric conversion technologies to address the energy crisis has become a core task in current scientific research. Photovoltaic technology and photoelectrochemical water splitting for hydrogen production, as two important directions in solar energy utilization, play crucial roles in power supply and chemical fuel production, respectively. How to construct an integrated system that combines photovoltaic power generation and photoelectrochemical hydrogen production functions, and significantly improve its photoelectric conversion efficiency and stability, has become a critical scientific problem urgently needing to be solved in the field of energy materials.

[0003] As a representative of III-V compound semiconductors, gallium arsenide (GaAs) possesses excellent optoelectronic properties such as a direct bandgap, high carrier mobility, and high light absorption coefficient, exhibiting extremely high theoretical efficiency in both photovoltaic power generation and photoelectrochemical conversion. It is an ideal candidate material for overcoming the performance bottlenecks of existing devices. However, the fabrication cost of high-performance GaAs devices is high, and in photoelectrochemical applications, GaAs electrodes are highly susceptible to photocorrosion in strongly corrosive electrolyte environments, leading to a significant reduction in device lifetime and limiting its large-scale practical application in photovoltaic-photoelectrochemical integrated systems.

[0004] To improve the optical response range and charge collection efficiency of traditional gallium arsenide-based pn junction devices, the conventional approach is to construct a multi-junction stacked structure by epitaxially growing III-V group semiconductors with different band gaps. However, as the number of junctions increases, not only does the fabrication process become extremely complex, leading to a sharp increase in cost, but severe lattice mismatch inevitably exists between the epitaxial layers, introducing a large number of interface defects. This, in turn, limits the separation and transport efficiency of photogenerated carriers, thus restricting further improvements in photovoltaic and photoelectrochemical performance.

[0005] How to effectively improve the carrier separation and transport capabilities of gallium arsenide heterojunctions in photovoltaic-photoelectric chemical integrated devices, and thus enhance photoelectric conversion efficiency, is one of the problems that needs to be solved. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to propose a composite hole transport thin film / gallium arsenide heterojunction photoelectrode, its fabrication, and its application in photovoltaic-photoelectrochemical integrated devices. This invention utilizes a ternary composite of carbon nanotubes, benzo[a]pyrrole dione compounds, and graphene oxide. By leveraging the synergistic effect of these three components, the carrier separation and transport capabilities of the carbon nanotube / gallium arsenide heterojunction are further optimized, significantly improving the overall performance of the gallium arsenide heterojunction photoelectrode in photovoltaic power generation and photoelectrochemical conversion. This invention fully utilizes the hole transport characteristics of carbon nanotubes, benzo[a]pyrrole dione compounds, and graphene oxide, and significantly enhances the interfacial compatibility and chemical stability between the composite film and the gallium arsenide substrate. The benzo[a]pyrrole dione compounds uniformly penetrate into the cross-linked network of the carbon nanotubes, increasing the contact area and accelerating carrier separation. Simultaneously, graphene oxide, as a two-dimensional transition component, achieves deep matching with the gallium arsenide energy levels, effectively reducing energy loss at the interface. The photoelectrode of this invention improves the photoelectric conversion efficiency of photovoltaic-photoelectrochemical integrated devices.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A composite hole transport thin film / gallium arsenide heterojunction photoelectrode includes a back electrode, a gallium arsenide substrate, and a composite hole transport thin film arranged sequentially from bottom to top.

[0009] The composite hole transport thin film is prepared by the following method:

[0010] Carbon nanotube films were fabricated on gallium arsenide substrates, benzo[a]pyrrole dione films were spin-coated onto the carbon nanotube films, and graphene oxide films were fabricated on the benzo[a]pyrrole dione films.

[0011] The composite hole transport film is in complete contact with the gallium arsenide substrate.

[0012] The benzodipyrrole dione film is prepared from benzodipyrrole dione compounds;

[0013] Benzodipyrrole diones:

[0014] R is an alkyl group.

[0015] The benzodipyrrole dione compound is preferably...

[0016] In the structure, dashed lines indicate connection points.

[0017] The carbon nanotube film is obtained by filtration of a carbon nanotube dispersion.

[0018] The concentration of the carbon nanotube dispersion was (1.26~1.28)×10⁻⁶. -3 mg / mL. The thickness of the carbon nanotube film is 18~60 nm.

[0019] The carbon nanotubes have a diameter of 1-2 nm and a length of 1-3 μm.

[0020] The carbon nanotube dispersion is prepared by dispersing carbon nanotubes in a sodium dodecylbenzenesulfonate solution with a mass fraction of 0.2-0.8%.

[0021] The benzodipyrrole dione film was obtained by spin-coating a benzodipyrrole dione compound solution onto a carbon nanotube film.

[0022] The concentration of benzodipyrrole dione compounds in the solution is 1-20 mg / mL, and the solvent is chlorobenzene.

[0023] The thickness of the benzodipyrrole dione film is 20~80 nm.

[0024] The spin coating speed is 3000-5000 r / min.

[0025] The graphene oxide film was prepared by electrochemical deposition. The electrochemical deposition conditions were: initial potential 0.6 V, termination potential 1.5 V, scan rate 50 mV / s, and number of cycles 1 to 5.

[0026] The thickness of the back electrode is 100~130mm.

[0027] The back electrode is one or more of the following: gold, silver, titanium, copper, nickel, platinum, antimony tin oxide, and aluminum doped with zinc oxide.

[0028] The method for fabricating the composite hole transport thin film / gallium arsenide heterojunction photoelectrode includes the following steps:

[0029] 1) A back electrode is fabricated on the back surface of a gallium arsenide substrate to obtain a back electrode / gallium arsenide substrate;

[0030] 2) A carbon nanotube thin film layer was prepared on the positive surface of a gallium arsenide substrate;

[0031] 3) A benzodipyrrole dione film was prepared on a carbon nanotube thin film by spin coating; a graphene oxide film was prepared on the benzodipyrrole dione film by electrochemical deposition to obtain a composite hole transport film / gallium arsenide heterojunction photoelectrode.

[0032] The photoelectrode is used in photovoltaic-photoelectrochemical integrated devices, particularly photovoltaic power generation-photoelectrochemical hydrogen production.

[0033] The photovoltaic-photoelectrochemical integrated device includes a photoelectrochemical water splitting hydrogen production device and a solar cell unit. The aforementioned photoelectrode is designated as photoelectrode A, serving as the photoanode of the photoelectrochemical water splitting hydrogen production device. Another aforementioned photoelectrode is designated as photoelectrode B, whose back electrode is connected to the back electrode of photoelectrode A in the photoelectrochemical water splitting hydrogen production device via a conductive material. Photoelectrode B is also connected in series with the back electrode of the solar cell unit via a conductive material, forming a closed-loop photovoltaic-photoelectrochemical integrated energy conversion device, i.e., a photovoltaic-photoelectrochemical integrated device.

[0034] This invention utilizes the ternary synergistic effect of carbon nanotubes, benzodipyrrole diones, and graphene oxide to further optimize the carrier separation and transport capabilities of carbon nanotube / gallium arsenide heterojunctions, significantly improving the overall performance of gallium arsenide heterojunction photoelectrodes in photovoltaic power generation and photoelectrochemical conversion. In this system, the combination of carbon nanotubes, benzodipyrrole diones, and graphene oxide fully leverages the hole transport characteristics of all three components and significantly enhances the interfacial compatibility and chemical stability between the composite film and the gallium arsenide substrate. Carbon nanotubes, with their excellent conductivity and mechanical strength, construct a highly efficient charge transport backbone, providing a low-impedance channel for carrier collection in photovoltaic power generation and charge injection in photoelectrochemical reactions. Benzodipyrrole diones not only exhibit good light absorption in the blue-green light region but also uniformly penetrate into the cross-linked network of carbon nanotubes, increasing the contact area and accelerating carrier separation. Furthermore, the generation and transfer efficiency of holes are optimized through band structure modulation. Meanwhile, graphene oxide plays a crucial role in interface passivation and energy level bridging, achieving deep matching with gallium arsenide energy levels, effectively reducing energy loss at the interface, and reducing recombination centers on the gallium arsenide surface.

[0035] This composite hole transport thin film can be prepared through simple filtration, transfer, and spin coating processes, which not only reduces production costs but also simplifies the material processing flow. The thin film of this invention not only advances the research of photovoltaic and photoelectrochemical integrated devices but also provides a technical path for the industrial application of high-performance, low-cost photovoltaic-photoelectrochemical integrated energy conversion systems.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] Compared to traditional carbon nanotube / gallium arsenide heterojunction structures, the ternary composite thin film of this invention achieves a significant improvement in photovoltaic power generation and photoelectrochemical conversion performance while maintaining the advantage of low-cost preparation. The film layer of this invention effectively solves the problem of poor contact between traditional carbon films and semiconductor interfaces. It not only improves the current density of photovoltaic devices by optimizing the interface energy level arrangement, but also enhances the chemical stability of the photoelectrochemical electrode in the electrolyte by forming a dense protective layer. Furthermore, the solution-based preparation process (such as vacuum filtration and spin coating) used in this invention does not rely on expensive vacuum deposition equipment, significantly reducing production costs and laying a solid foundation for the large-scale industrial application of gallium arsenide-based photovoltaic and photoelectrochemical integrated devices. This high-performance and economical technical solution not only effectively solves the bottleneck of high cost for high-performance semiconductor devices, but also provides an industrial path for promoting the high efficiency of photovoltaic power generation and photoelectrochemical hydrogen production technologies. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the composite hole transport thin film / gallium arsenide heterojunction photoelectrode of the present invention; wherein, 1-back electrode, 2-gallium arsenide substrate, 3-carbon nanotube thin film, 4-benzodipyrrole dione film layer, 5-graphene oxide film layer.

[0039] Figure 2 Linear scanning voltammetric curves of the photoelectrodes obtained in Examples 1-4 and Comparative Example 1;

[0040] Figure 3 Linear scanning voltammetry curves of the photoelectrodes obtained in Example 3 and Comparative Example 2;

[0041] Figure 4 The potential polarization diagrams of the photoelectrodes obtained in Example 3 and Comparative Example 2 are shown.

[0042] Figure 5 The graphs show the photoelectric conversion efficiency curves of the photoelectrodes obtained in Examples 1-4 and Comparative Example 1.

[0043] Figure 6 The photoelectrode obtained in Example 3 and Comparative Example 1 is used in a photovoltaic-photoelectrochemical integrated device, and the linear sweep voltammetry curve of the device is shown.

[0044] Figure 7 The graph shows the photoelectrochemical hydrogen and oxygen production rate of the photoelectrode obtained in Example 3 when used in a photovoltaic-photoelectrochemical integrated device.

[0045] Figure 8 This is a schematic diagram of the structure of the photoelectrode of the present invention used in a photovoltaic-photoelectrochemical integrated device; wherein 6-composite hole transport thin film / gallium arsenide heterojunction photoelectrode, 7-composite hole transport thin film / gallium arsenide heterojunction photoelectrode, and 8-platinum sheet electrode. Detailed Implementation

[0046] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents used in the embodiments can be obtained from commercially available sources.

[0047] A composite hole transport thin film / gallium arsenide heterojunction photoelectrode, the schematic diagram of which is shown below. Figure 1 As shown, it includes a back electrode 1, a gallium arsenide substrate 2, and a composite hole transport film arranged sequentially from bottom to top;

[0048] The composite hole transport thin film comprises, from bottom to top, a carbon nanotube film 3, a benzo[a]pyrrole dione film 4, and a graphene oxide film 5. The carbon nanotube film 3 is disposed on a gallium arsenide substrate 2.

[0049] The composite hole transport thin film is prepared by the following method:

[0050] A carbon nanotube film 3 is fabricated on a gallium arsenide substrate 2. A benzodipyrrole dione film 4 is prepared by spin-coating on the carbon nanotube film 3. A graphene oxide film 5 is prepared on the benzodipyrrole dione film 4.

[0051] Example 1

[0052] (1) A gallium arsenide substrate with a thickness of 3 mm and a size of 0.5 cm * 0.5 cm was ultrasonically cleaned in acetone and ethanol for 5 min, then acid-washed in 10 wt% HCl for 3 min, and then washed with deionized water and ethanol in sequence. After being dried with nitrogen, it can be used for the vapor deposition and annealing preparation of gold back electrode. The thickness of gold is 120 nm. The annealing conditions are: hold at 330℃ for 30 s, and finally obtain gold back electrode / gallium arsenide substrate.

[0053] (2) Before preparing the composite hole transport film on the surface of the gallium arsenide substrate, the back electrode / gallium arsenide substrate needs to be cleaned according to the cleaning process in step (1) and dried for later use.

[0054] (3) 1.27×10 -3 A 10 mg / mL carbon nanotube solution (carbon nanotubes with a diameter of 1-2 nm and a length of 1-3 μm; solvent is a 0.5% sodium dodecylbenzenesulfonate solution) was uniformly dispersed and then vacuum filtered to form a film. The obtained carbon nanotube film / filter film was placed on a clean gallium arsenide substrate and pressed firmly. After adding alcohol, the film was placed in a 70°C oven to dry. After the alcohol had completely evaporated, the film was removed and the filter film was removed to obtain a back electrode / gallium arsenide substrate / carbon nanotube film with a thickness of 20 nm.

[0055] (4) Prepare a 5 mg / mL benzodipyrrole dione / chlorobenzene solution and spin-coat the solution onto the back electrode / gallium arsenide / carbon nanotube film prepared in step (3). The spin-coating speed is 5000 r / min. The film thickness is controlled by changing the solution concentration to ensure the formation of a 50 nm organic film (benzodipyrrole dione film). Place it in a 90℃ oven to dry for 10 min, and then electrodeposit graphene oxide for 2 cycles. The electrochemical deposition conditions are: initial potential 0.6 V, termination potential 1.5 V, scan rate 50 mV / s, and number of cycles 2 to obtain the composite hole transport film / gallium arsenide heterojunction photoelectrode.

[0056] Two composite hole transport thin film / gallium arsenide heterojunction photoelectrodes are selected, denoted as photoelectrode A and photoelectrode B. Photoelectrode A serves as the photoanode of the photoelectrochemical device. The back electrodes of photoelectrode A and photoelectrode B are connected with a conductive material, and the back electrode of photoelectrode A is connected to a platinum sheet in the photoelectrochemical device. The photoelectrochemical device includes photoelectrode A and the platinum sheet electrode. Then, photoelectrode B is connected in series with a solar cell unit to construct a photovoltaic-photoelectrochemical integrated device forming a closed loop. A schematic diagram of the structure of the composite hole transport thin film / gallium arsenide heterojunction used in the photovoltaic-photoelectrochemical integrated device of the present invention is shown below. Figure 8 As shown, 6-composite hole transport film / gallium arsenide heterojunction photoelectrode (i.e., photoelectrode B), 7-composite hole transport film / gallium arsenide heterojunction photoelectrode (i.e., photoelectrode A), and 8-platinum sheet electrode.

[0057] Benzodipyrroledione:

[0058] .

[0059] The current density of the composite hole transport thin film / gallium arsenide heterojunction photoelectrode obtained in this embodiment can reach 16.06 mA·cm at 1.23 V. -2 (See Figure 2 The photoelectric conversion efficiency reached a maximum of 13.90% (see...). Figure 5 ).

[0060] Example 2

[0061] The preparation and parameters were the same as in Example 1, except for the preparation of the composite hole transport film. The concentration of the benzo[a]pyrrole dione / chlorobenzene solution was 8 mg / ml, and the thickness was 50 nm. Other preparation parameters remained unchanged, resulting in a photoelectrode structure essentially identical to that of Example 1.

[0062] The current density of the composite hole transport thin film / gallium arsenide heterojunction photoelectrode obtained in this embodiment can reach 16.27 mA·cm at 1.23 V. -2 (See Figure 2The photoelectric conversion efficiency reached a maximum of 16.76% (see...). Figure 5 ).

[0063] Example 3

[0064] The preparation and parameters were the same as in Example 1, except for the preparation of the composite hole transport film. The concentration of the benzo[a]pyrrole dione / chlorobenzene solution was 10 mg / ml, and other preparation parameters remained unchanged, resulting in a photoelectrode structure that was essentially the same as in Example 1.

[0065] The current density of the composite hole transport thin film / gallium arsenide heterojunction photoelectrode obtained in this embodiment can reach 19.69 mA·cm at 1.23 V. -2 (See Figure 2 In the potentiostatic polarization test, the current density was 12.04 mA·cm⁻¹. -2 Increased to 13.02 mA·cm -2 (See Figure 4 The highest photoelectric conversion efficiency reached 18.43% (see...). Figure 5 When assembled into a photovoltaic-photoelectrochemical integrated device, the current density can reach 22.83 mA·cm at 0 V. -2 (See Figure 6 The photoelectrochemical hydrogen production rate reached 4.144 μmol / min (see...). Figure 7 ).

[0066] Example 4

[0067] The preparation and parameters were the same as in Example 1, except for the preparation of the composite hole transport film. The concentration of the benzo[a]pyrroledione / chlorobenzene solution was 20 mg / ml, and other preparation parameters remained unchanged, resulting in a photoelectrode structure that was essentially the same as in Example 1.

[0068] The current density of the composite hole transport thin film / gallium arsenide heterojunction photoelectrode obtained in this embodiment can reach 17.42 mA·cm at 1.23 V. -2 (See Figure 2 The photoelectric conversion efficiency reached a maximum of 15.31% (see...). Figure 5 ).

[0069] Comparative Example 1

[0070] The preparation and parameters were the same as in Example 1, except that only the carbon nanotube film was used as the hole transport film, without the benzodipyrrole dione film and the graphene oxide film layer. Other preparation parameters remained unchanged, resulting in a carbon nanotube film / gallium arsenide heterojunction photoelectrode.

[0071] The current density of the carbon nanotube thin film / gallium arsenide heterojunction photoelectrode obtained in this comparative example can reach 12.78 mA·cm at 1.23 V. -2 (See Figure 2 The highest photoelectric conversion efficiency reached 12.62% (see...). Figure 5 When assembled into a photovoltaic-photoelectrochemical integrated device, the current density can reach 11.07 mA·cm at 0 V. -2 (See Figure 6 ).

[0072] Comparative Example 2

[0073] The preparation and parameters were the same as in Example 1, except that a carbon nanotube film / benzodipyrrole dione composite film was used as the hole transport film, without an oxide graphene film layer, and other preparation parameters remained unchanged, resulting in a hole transport film / gallium arsenide heterojunction photoelectrode.

[0074] The hole transport thin film / gallium arsenide heterojunction photoelectrode obtained in this comparative example achieves a current density of 18.72 mA·cm⁻¹ at 1.23 V. -2 (See Figure 3 In the potentiostatic polarization test, the current density was 11.80 mA·cm⁻¹. -2 Attenuation to 9.92 mA·cm -2 (See Figure 4 ).

[0075] Figure 2 Linear scanning voltammetric curves of the photoelectrodes obtained in Examples 1-4 and Comparative Example 1;

[0076] Figure 3 Linear scanning voltammetry curves of the photoelectrodes obtained in Example 3 and Comparative Example 2;

[0077] Figure 4 The potential polarization diagrams of the photoelectrodes obtained in Example 3 and Comparative Example 2 are shown.

[0078] Figure 5 The graphs show the photoelectric conversion efficiency curves of the photoelectrodes obtained in Examples 1-4 and Comparative Example 1.

[0079] Figure 6 The photoelectrode obtained in Example 3 and Comparative Example 1 is used in a photovoltaic-photoelectrochemical integrated device, and the linear sweep voltammetry curve of the device is shown.

[0080] Figure 7 The graph shows the photoelectrochemical hydrogen and oxygen production rate of the photoelectrode obtained in Example 3 when used in a photovoltaic-photoelectrochemical integrated device.

Claims

1. A composite hole transport thin film / gallium arsenide heterojunction photoelectrode, characterized in that: The components, arranged sequentially from bottom to top, include a back electrode, a gallium arsenide substrate, and a composite hole transport thin film. The composite hole transport thin film is prepared by the following method: Carbon nanotube films were fabricated on gallium arsenide substrates, benzo[a]pyrrole dione films were spin-coated on the carbon nanotube films, and graphene oxide films were fabricated on the benzo[a]pyrrole dione films. The benzodipyrrole dione film is prepared from benzodipyrrole dione compounds; Benzodipyrrole diones: R is an alkyl group.

2. The composite hole transport thin film / gallium arsenide heterojunction photoelectrode according to claim 1, characterized in that: The thickness of the carbon nanotube film is 18-60 nm; The thickness of the benzodipyrrole dione film is 20-80 nm; The structure of the benzodipyrrole dione compound is as follows: In the structural formula, the dashed line in R indicates the connection position; The thickness of the graphene oxide film is limited by the number of electrodeposition passes, which is 1-5 passes.

3. The composite hole transport thin film / gallium arsenide heterojunction photoelectrode according to claim 1, characterized in that: The carbon nanotube film was prepared by vacuum filtration; specifically, carbon nanotubes were dispersed in a sodium dodecylbenzenesulfonate solution to obtain a carbon nanotube dispersion; then, the dispersion was filtered to form a film, which was then transferred onto a gallium arsenide substrate; the concentration of the carbon nanotube dispersion was (1.26~1.28)×10⁻⁶. -3 mg / mL; The benzodipyrrole dione film was prepared by spin coating; specifically, a benzodipyrrole dione compound was prepared into a solution, spin-coated onto a carbon nanotube film, and dried; the concentration of the benzodipyrrole dione compound solution was 1-20 mg / mL. The graphene oxide film was prepared by electrochemical deposition; the electrochemical deposition conditions were: initial potential 0.6 V, termination potential 1.5 V, scan rate 50 mV / s, and number of cycles 1-5.

4. The composite hole transport thin film / gallium arsenide heterojunction photoelectrode according to claim 3, characterized in that: The concentration of the sodium dodecylbenzenesulfonate solution is 0.2~0.8 wt%; The carbon nanotubes have a diameter of 1-2 nm and a length of 1-3 μm; the spin coating speed during the preparation of the benzo[a]pyrrole dione film is 3000-5000 r / min; and the number of electrodeposition cycles during the preparation of the graphene oxide film is 1-5.

5. The composite hole transport thin film / gallium arsenide heterojunction photoelectrode according to claim 1, characterized in that: The back electrode is one or more of gold, silver, titanium, copper, nickel, platinum, tin oxide, antimony oxide, or aluminum doped with zinc oxide; The thickness of the back electrode is 100~130nm.

6. The method for fabricating the composite hole transport thin film / gallium arsenide heterojunction photoelectrode according to any one of claims 1 to 5, characterized in that: 1) A back electrode is fabricated on the back surface of a gallium arsenide substrate to obtain a back electrode / gallium arsenide substrate; 2) Carbon nanotube films were prepared on the positive surface of a gallium arsenide substrate; 3) A benzo[2]pyrrole dione film was prepared by spin-coating on a carbon nanotube film, and then a graphene oxide film was electrodeposited on the benzo[2]pyrrole dione film to obtain a composite hole transport film / gallium arsenide heterojunction photoelectrode.

7. The application of the composite hole transport thin film / gallium arsenide heterojunction photoelectrode according to any one of claims 1 to 5, characterized in that: The composite hole transport thin film / gallium arsenide heterojunction photoelectrode is used in photovoltaic-photoelectric chemical integrated devices.

8. The application according to claim 7, characterized in that: The term "photoelectrochemistry" refers to the photoelectrochemical electrolysis of water to produce hydrogen.

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