Heterojunction, preparation method and application thereof

Abstract

The invention provides a heterojunction, a preparation method and application thereof, and relates to the technical field of photovoltaic materials. The heterojunction is a ZnO nano array / Sb2S3 heterojunction, the problem that the carrier transport capacity of the Sb2S3 thin film is insufficient can be well solved, and therefore the conductivity of the Sb2S3 thin film is improved, the carrier transport performance of the whole device is enhanced, and the short-circuit current density and the photoelectric conversion efficiency of the Sb2S3 solar cell can be greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic materials technology, and relates to a heterojunction, its preparation method and its application. Background Technology

[0002] In recent years, antimony sulfide (Sb₂S₃) has gained attention due to its ideal optical band gap (1.7-1.8 eV) and high absorption coefficient (α≈10). 5 cm -1 With its excellent stability and low-temperature preparation characteristics, Sb2S3 solar cells have become a research hotspot in the photovoltaic field. However, the efficiency of current Sb2S3 solar cells is still limited to below 8.5%, significantly lagging behind traditional photovoltaic technologies such as CIGS (23.6%) and CdTe (23.1%), and even falling short of its family of materials Sb2(S,Se)3 (10.92% and Sb2Se3 (10.57%)) and their theoretical limits.

[0003] Vacuum and hydrothermal methods are the main methods for preparing Sb₂S₃ solar cells. Sb₂S₃ films prepared by the hydrothermal method are predominantly [hk₀] oriented with poor proximity, severely limiting the film's electron transport capability. Sb₂S₃ films prepared by the vacuum method are more likely to achieve a [hk₁] orientation and exhibit excellent crystallinity; however, due to the loss of sulfur during deposition, a large number of sulfur vacancies exist in the film, limiting the light response performance of Sb₂S₃ solar cells.

[0004] Regardless of whether Sb₂S₃ solar cells are fabricated using vacuum or non-vacuum methods (such as hydrothermal methods), most employ CdS thin films as the contact layer. The CdS film plays a crucial role in controlling the crystallization and growth orientation of the subsequent Sb₂S₃ film. However, due to limitations in the thermal stability of the CdS / Sb₂S₃ heterojunction and the parasitic absorption losses inherent in the CdS film, the CdS film thickness is often relatively thin. At excessively high deposition or annealing temperatures, the performance of the CdS / Sb₂S₃ heterojunction in localized areas is easily compromised (especially on FTO substrates with high roughness), severely deteriorating the performance matching of the CdS / Sb₂S₃ heterojunction interface, as well as the growth orientation, defect concentration, and compactness of the subsequent Sb₂S₃ film. Therefore, developing more stable and high-performance heterojunction technologies is of great significance and importance for improving the performance of Sb₂S₃ solar cells. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a heterojunction, its preparation method, and its application.

[0006] The technical solution of the present invention is as follows:

[0007] A heterojunction, wherein the heterojunction is a ZnO nanoarray / Sb2S3 heterojunction.

[0008] Preferably, the thickness of the ZnO nanoarray is 0.5-1.5 μm; The thickness of the Sb2S3 is 200-600 nm.

[0009] A method for preparing a heterojunction as described in any of the above embodiments, comprising the steps of: A ZnO seed layer was prepared on the surface of the substrate by spin coating to obtain a pre-coated substrate. A ZnO nanoarray is formed on one side of the pre-coated substrate containing the ZnO seed layer; A thin film of Sb2S3 is formed on the surface of the ZnO nanoarray.

[0010] Preferably, the substrate is FTO glass; The spin coating solution used for spin coating consists of: 1-1.5 mmol of a first water-soluble zinc salt, 4 mL of an ether or ester organic solvent, 0.5 mL of isopropanol, and 120 μL of ethanolamine; The first water-soluble zinc salt is selected from one or a combination of two or more of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc acetate dihydrate, and zinc citrate.

[0011] More preferably, the spin-coating solution is annealed in air at 300°C for 30 minutes after spin-coating.

[0012] Preferably, the formation of the ZnO nanoarray is as follows: the pre-coated substrate is immersed in the deposition solution and sealed, heated at 90-100°C for 2-3 hours, removed, washed and dried, and annealed in hot air at 300°C for 30 minutes; The deposition solution consisted of 8-12 mmol of a second water-soluble zinc salt, 240 mL of deionized water, and 4.5 mL of ammonia. The second water-soluble zinc salt is selected from one or a combination of two or more of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc acetate dihydrate, and zinc citrate.

[0013] Preferably, the formation of the Sb2S3 thin film is achieved by vacuum deposition using Sb2S3 powder.

[0014] More preferably, the purity of the Sb2S3 powder is not less than 99.999%; The vacuum deposition temperature is 550-550℃, the time is 60-90s, and the vacuum degree does not exceed 0.5Pa.

[0015] More preferably, in the vacuum deposition, the evaporation source is 12.5 cm from the edge of the temperature zone, and the ZnO nanoarray is 2.7 cm from the edge of the temperature zone.

[0016] An application of a heterojunction prepared by any of the above embodiments or by any of the preparation methods described in the embodiments, for use in indoor photovoltaics, photoelectric water splitting, photodetectors, or solar cells.

[0017] The beneficial effects of this invention are: (1) This invention proposes for the first time a ZnO nanoarray / Sb2S3 heterojunction structure. The ZnO nanoarray effectively induces the vertical orientation growth of the Sb2S3 film, which solves the problem of insufficient orientation of the absorber layer [hk1] of the current Sb2S3 solar cell and effectively improves the carrier transport performance of the Sb2S3 film.

[0018] (2) The ZnO nanoarray / Sb2S3 heterojunction proposed in this invention has stable structural performance, which not only solves the parasitic loss problem caused by traditional CdS thin film, but also effectively improves the light response performance of Sb2S3 solar cell. Attached Figure Description

[0019] Figure 1 The morphology of the heterojunction in Example 1 and Comparative Example 1 is compared.

[0020] Figure 2 The comparison shows the GIXRD results of the heterojunction in Example 1 and the comparative example 1.

[0021] Figure 3 The absorption curves and optically fitted bandgap values ​​of the heterojunctions in Example 1 and Comparison 1 are compared. Among them, (a) is a comparison of absorption curves, and (b) is a comparison of optical fitting bandgap values.

[0022] Figure 4 A comparison of the JV characteristic curves of the heterojunction-assembled solar cells of Example 1 and Comparative Example 1.

[0023] Figure 5 Comparison of external quantum efficiency curves for the heterojunction-assembled solar cells of Example 1 and Comparative Example 1. Detailed Implementation

[0024] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0025] On the one hand, the present invention proposes a heterojunction, which is a ZnO nanoarray / Sb2S3 heterojunction.

[0026] This invention uses a ZnO nanoarray as a contact layer, which effectively induces the vertical orientation growth of the Sb2S3 thin film, solving the problem of insufficient orientation of the absorber layer [hk1] in current Sb2S3 solar cells. This effectively improves the carrier transport performance of the Sb2S3 thin film, and the resulting ZnO nanoarray / Sb2S3 heterojunction has stable structural performance. It not only solves the parasitic loss problem caused by using traditional CdS thin films as contact layers, but also effectively improves the light response performance of Sb2S3 solar cells.

[0027] In some embodiments, the thickness of the ZnO nanoarray is 0.5-1.5 μm; The thickness of Sb2S3 is 200-600 nm.

[0028] For example, the thickness of ZnO nanoarrays can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, etc.; the thickness of Sb2S3 can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, etc.

[0029] On the other hand, the present invention also proposes a method for preparing a heterojunction as described in any of the above embodiments, the steps of which include: A ZnO seed layer was prepared on the surface of the substrate by spin coating to obtain a pre-coated substrate. A ZnO nanoarray is formed on one side of a pre-coated substrate containing a ZnO seed layer; A Sb2S3 thin film is formed on the surface of the ZnO nanoarray, thus obtaining the desired result.

[0030] The present invention first forms a ZnO seed layer on the substrate surface, and then forms a ZnO nanoarray on the substrate surface through the induction effect of the seed layer. Then, an Sb2S3 thin film is formed on the surface of the ZnO nanoarray to obtain a ZnO nanoarray / Sb2S3 heterojunction.

[0031] In some embodiments, the substrate is FTO glass; The spin coating solution used for spin coating consists of: 1-1.5 mmol of the first water-soluble zinc salt, 4 mL of ether or ester organic solvent, 0.5 mL of isopropanol and 120 μL of ethanolamine; The first water-soluble zinc salt is selected from one or a combination of two or more of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc acetate dihydrate, and zinc citrate.

[0032] In some embodiments, the spin-coating solution is annealed in air at 300°C for 30 min after spin coating.

[0033] Nano-ZnO seed layers can be obtained by spin-coating a solution containing water-soluble zinc salts onto a substrate surface and then annealing.

[0034] In some embodiments, the ZnO nanoarray is formed by: immersing the pre-coated substrate in the deposition solution and sealing it, heating it at 90-100°C for 2-3 hours, removing it, washing it dry, and annealing it in hot air at 300°C for 30 minutes. The deposition solution consisted of 8-12 mmol of the second water-soluble zinc salt, 240 mL of deionized water, and 4.5 mL of ammonia. The second water-soluble zinc salt is selected from one or a combination of two or more of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc acetate dihydrate, and zinc citrate.

[0035] ZnO nanoarrays can be formed on a substrate surface via a hydrothermal reaction, utilizing the inductive effect of a nano-ZnO seed layer. There are no particular restrictions on the conditions for the hydrothermal reaction; heating at 90℃ for 2 hours, 90℃ for 3 hours, 100℃ for 2 hours, or 100℃ for 3 hours are all acceptable.

[0036] In some embodiments, the Sb2S3 thin film is formed by vacuum deposition using Sb2S3 powder.

[0037] In some embodiments, the purity of the Sb₂S₃ powder is not less than 99.999%; The vacuum deposition temperature is 550-550℃, the time is 60-90s, and the vacuum degree does not exceed 0.5Pa.

[0038] In some embodiments, during vacuum deposition, the evaporation source is 12.5 cm from the edge of the temperature zone, and the ZnO nanoarray is 2.7 cm from the edge of the temperature zone.

[0039] Furthermore, the present invention also proposes an application of the heterojunction prepared by the preparation method described in any of the above embodiments, for use in indoor photovoltaics, photoelectric water splitting, photodetectors, or solar cells.

[0040] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0041] Example 1 0.246 g (1.12 mmol) of zinc acetate dihydrate was dissolved in 4 mL of ethylene glycol monomethyl ether, followed by the addition of 0.5 mL of isopropanol and 120 μL of ethanolamine. The mixture was stirred until homogeneous to obtain a spin-coating solution. The spin-coating solution was then spin-coated onto a clean FTO substrate at a spin speed of 2500 rpm, an acceleration of 1000 r / s, and a spin-coating time of 20 s. After spin-coating, the substrate was first dried on an 80°C hot stage, and then transferred to a 300°C hot stage for air annealing for 30 min to obtain a pre-coated substrate with a spin-coated ZnO seed layer.

[0042] 2.106 g (9.6 mmol) of zinc acetate dihydrate was dissolved in 240 mL of deionized water. Then, 4.5 mL of ammonia was slowly added while stirring until a clear deposition solution was obtained. The pre-coated substrate was then immersed in the deposition solution, sealed with aluminum foil, and placed in a 90°C water bath for a hydrothermal reaction for 120 min. After the reaction, the substrate was removed, rinsed with deionized water, and dried. Finally, it was air-annealed at 300°C for 30 min to obtain a ZnO nanoarray.

[0043] 40 mg of 99.999% pure Sb₂S₃ powder was placed in a heating source, with the evaporation source positioned 12.5 cm from the edge of the heating zone and the ZnO nanoarray positioned 2.7 cm from the edge of the heating zone. A vapor-transfer sedimentation (VTD) evaporation program was set to raise the temperature from room temperature (25 °C) to 510 °C in 690 s, and then held at 510 °C for 80 s. Once the vacuum level in the vacuum chamber dropped below 0.5 Pa, the program was run to deposit the Sb₂S₃ thin film. After the deposition process, the evaporation source was allowed to cool naturally from 400 °C, and then rapidly cooled to room temperature to obtain a ZnO nanoarray / Sb₂S₃ heterojunction.

[0044] Example 2 The difference between this embodiment and Example 1 is that in Example 1, the hydrothermal reaction for preparing the ZnO nanoarray was changed from 90℃ for 120 min to 90℃ for 140 min. The remaining steps remain unchanged.

[0045] Example 3 The difference between this embodiment and Example 1 is that in Example 1, the zinc acetate dihydrate was adjusted from 9.6 mmol to 8 mmol when preparing the ZnO nanoarray. The remaining steps remained unchanged.

[0046] Example 4 The difference between this embodiment and Example 1 is that in Example 1, when preparing the ZnO nanoarray, the zinc acetate dihydrate was adjusted to 12 mmol of zinc citrate, and the hydrothermal reaction was changed from 90℃ for 120 min to 100℃ for 3 h. The remaining steps remained unchanged.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that in Example 1, the ZnO nanoarray was replaced with a CdS thin film, as detailed below: 32 mL of 15 mmol / L CdSO4 solution, 16 mL of 1.5 mol / L thiourea solution, 40 mL of ammonia water, and 220 mL of deionized water were placed in a beaker and preheated in a 66 °C water bath for 2 min. Then, 16 mL of thiourea was added, and a clean FTO glass was placed in the beaker. After deposition in a 66 °C water bath for 22 min, the glass was removed, rinsed, and dried to obtain an FTO glass with a CdS film deposited on it.

[0048] FTO glass with CdS film deposited was vacuum deposited with Sb2S3 film according to the method in Example 1 to obtain CdS / Sb2S3 heterojunction.

[0049] The morphology (SEM images) of the ZnO nanoarray / Sb₂S₃ heterojunction in Example 1 and the CdS / Sb₂S₃ heterojunction in Comparative Example 1 are compared below. Figure 1 As shown, the left image (a) shows the CdS / Sb₂S₃ heterojunction of Comparative Example 1, and the right image (b) shows the ZnO nanoarray / Sb₂S₃ heterojunction. The Sb₂S₃ film of Comparative Example 1 has a dense morphology and rounded, full grains, but it is irregular. In contrast, in Example 1, under the induction of the ZnO nanoarray, the overall grains of the Sb₂S₃ film are more regular and uniform. Combining the cross-sectional morphology of the two, it can be seen that, at the same film thickness, the Sb₂S₃ film prepared by the ZnO nanoarray (Example 1) exhibits significant columnar growth, while the Sb₂S₃ film prepared based on the CdS contact layer (Comparative Example 1) shows more disordered growth.

[0050] Appendix Figure 2 A comparison of grazing incidence X-ray diffraction (GIXRD, grazing incidence angle 0.3°) results for Sb₂S₃ thin films of Example 1 and Comparative Example 1 is shown. The left image (a) is a GIXRD comparison, and the right image (b) is a histogram of the relevant crystal texture coefficients of the two Sb₂S₃ thin films. CdS / Sb₂S₃ represents Comparative Example 1, and ZnO / Sb₂S₃ represents Example 1. Figure 2 (a) It can be seen that both heterojunction techniques can induce the preparation of orthorhombic Sb₂S₃ thin films with good crystallinity. The difference lies in the fact that the Sb₂S₃ thin film based on the CdS contact layer (Comparative Example 1) exhibits a preferred growth characteristic of (200), (120), and (130) crystal planes (hk0). In contrast, the Sb₂S₃ thin film based on the ZnO nanoarray (Example 1) exhibits a preferred growth characteristic of (211), (221), and (002) crystal planes (hk1). Figure 2As shown in (b), the calculation and analysis of the characteristic crystal plane texture coefficients show that, compared to the CdS contact layer, the ZnO nanoarray can effectively suppress the [hk0] orientation growth and promote the [hk1] orientation growth of the Sb2S3 thin film, which can effectively improve the carrier transport capacity of the Sb2S3 thin film. Therefore, combined with the SEM analysis results, it can be seen that the ZnO nanoarray / Sb2S3 heterojunction structure technology of Example 1 can effectively enhance the carrier transport of the Sb2S3 thin film.

[0051] For example, see attached Figure 3 As shown, Figure 3 (a) shows the absorption curves for comparison. Figure 3 (b) Comparison of optical bandgap values, where CdSfilm represents Comparative Example 1 and ZnO array represents Example 1. The results show that the ZnO nanoarray / Sb2S3 heterojunction of Example 1 can effectively reduce the parasitic absorption loss of the front interface electron transport layer on incident light, which is beneficial to the full absorption and utilization of incident light by the Sb2S3 thin-film solar cell, thereby obtaining a better short-circuit current. This is mainly attributed to the fact that the ZnO nanoarray (3.31 eV) has a higher optical bandgap value than the CdS contact layer (2.36 eV), indicating that the ZnO nanoarray / Sb2S3 heterojunction structure technology of Example 1 can effectively suppress the parasitic absorption loss of the Sb2S3 thin film.

[0052] To further demonstrate the performance enhancement effect of ZnO nanoarray / Sb2S3 heterojunction structure technology on Sb2S3 thin-film solar cells, top-mass Sb2S3 solar cells were assembled according to the device structures of FTO / CdS / Sb2S3 / Spiro-OMeTAD / Au (Comparative Example 1) or FTO / ZnO array / Sb2S3 / Spiro-OMeTAD / Au (Examples 1-4). The performance results of the solar cells are shown in Table 1 below. A comparison between Example 1 and Comparative Example 1 is attached. Figure 4 (Comparison of JV characteristic curves) and appendix Figure 5 (External quantum efficiency EQE curves) are shown, where TFSC-C represents FTO / CdS / Sb2S3 / Spiro-OMeTAD / Au (Comparative Example 1), and TFSC-Z represents FTO / ZnO array / Sb2S3 / Spiro-OMeTAD / Au (Example 1).

[0053] Table 1

[0054] As attached Figure 4As shown, the open-circuit voltage of the TFSC-Z device is significantly lower than that of the TFSC-C device. This is because the ZnO nanoarray / Sb₂S₃ heterojunction has a larger conduction band mismatch value compared to the CdS / Sb₂S₃ heterojunction. In addition, the short-circuit current of the TFSC-Z device is increased by 37.1% compared to the TFSC-C device, while the fill factor remains almost unchanged. This results in a higher photoelectric conversion efficiency for the TFSC-Z device compared to the TFSC-C device (similar conclusions can be found in Examples 2-4). The increase in short-circuit current is mainly attributed to several advantages of the ZnO nanoarray / Sb₂S₃ heterojunction structure technology: 1) inducing vertical orientation growth of Sb₂S₃; 2) suppressing parasitic absorption losses; and 3) providing an efficient transport channel for photogenerated electrons through the ZnO nanoarray.

[0055] As attached Figure 5 As shown, the TFSC-C device exhibits poor quantum response performance in the 300-800 nm wavelength range, indicating insufficient vertical orientation growth of the Sb₂S₃ thin film induced by the CdS contact layer. Furthermore, the S vacancy defects introduced by S element loss during the Sb₂S₃ thin film vacuum deposition process are also a significant factor contributing to the non-ideal quantum response performance of the TFSC-C device. The ZnO nanoarray / Sb₂S₃ heterojunction in Example 1 can effectively improve the EQE performance of Sb₂S₃ solar cells in the 360-800 nm wavelength range. (See attached image) Figure 5 The results demonstrate the superiority of the ZnO nanoarray / Sb₂S₃ heterojunction in suppressing parasitic absorption losses and enhancing the vertical orientation of the Sb₂S₃ thin film, thereby improving the carrier transport performance of the device. Furthermore, the integral JSC extracted from the EQE data shows good agreement with the JV results, proving the accuracy of the results. Therefore, the novel ZnO nanoarray / Sb₂S₃ heterojunction proposed in this invention can effectively solve the problem of insufficient carrier transport capacity in Sb₂S₃ thin films, thereby improving the conductivity of the Sb₂S₃ thin film and enhancing the overall carrier transport performance of the device, significantly improving the short-circuit current density and photoelectric conversion efficiency of Sb₂S₃ solar cells.

[0056] Therefore, the contact layer plays a crucial role in regulating the growth orientation characteristics of the Sb₂S₃ thin film and determines the heterojunction quality and the photoelectric conversion efficiency of the Sb₂S₃ thin-film solar cell. This invention proposes a novel ZnO nanoarray / Sb₂S₃ heterojunction technology for the first time, which has the following advantages: 1) It can effectively enhance the [hk1] orientation of the Sb₂S₃ thin film and suppress the [hk0] orientation growth; 2) It can effectively suppress the parasitic absorption loss of the Sb₂S₃ solar cell, achieving sufficient light absorption and significantly enhancing the short-circuit current density of the device; 3) The ZnO nanoarray can provide an efficient transport channel for the transport and collection of photogenerated electrons. Benefiting from the advantages of the ZnO nanoarray / Sb₂S₃ heterojunction, the Sb₂S₃ solar cell based on this heterojunction technology ultimately achieves a higher photoelectric conversion efficiency than CdS / Sb₂S₃ heterojunction structure devices. Therefore, the ZnO nanoarray / Sb2S3 heterojunction technology of the present invention will provide a new reference for optimizing the growth orientation and controlling carrier transport of Sb2S3 thin films, which will help promote the performance improvement and industrialization of Sb2S3 thin film solar cells.

[0057] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A heterojunction, characterized in that, The heterojunction is a ZnO nanoarray / Sb2S3 heterojunction.

2. The heterojunction according to claim 1, characterized in that, The thickness of the ZnO nanoarray is 0.5-1.5 μm; The thickness of the Sb2S3 is 200-600 nm.

3. A method for preparing a heterojunction as described in claim 1 or 2, characterized in that the step... include: A ZnO seed layer was prepared on the surface of the substrate by spin coating to obtain a pre-coated substrate. A ZnO nanoarray is formed on one side of the pre-coated substrate containing the ZnO seed layer; A thin film of Sb2S3 is formed on the surface of the ZnO nanoarray.

4. The preparation method according to claim 3, characterized in that, The substrate is FTO glass; The spin coating solution used for spin coating consists of: 1-1.5 mmol of a first water-soluble zinc salt, 4 mL of an ether or ester organic solvent, 0.5 mL of isopropanol, and 120 μL of ethanolamine; The first water-soluble zinc salt is selected from one or a combination of two or more of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc acetate dihydrate, and zinc citrate.

5. The preparation method according to claim 4, characterized in that, The spin-coating solution was then annealed in air at 300°C for 30 minutes after spin-coating.

6. The preparation method according to claim 3, characterized in that, The formation of the ZnO nanoarray is as follows: the pre-coated substrate is immersed in the deposition solution and sealed, heated at 90-100℃ for 2-3 hours, taken out, washed and dried, and annealed in hot air at 300℃ for 30 minutes. The deposition solution consisted of 8-12 mmol of a second water-soluble zinc salt, 240 mL of deionized water, and 4.5 mL of ammonia. The second water-soluble zinc salt is selected from one or a combination of two or more of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, zinc acetate dihydrate, and zinc citrate.

7. The preparation method according to claim 3, characterized in that, The Sb2S3 thin film is formed by vacuum deposition using Sb2S3 powder.

8. The preparation method according to claim 7, characterized in that, The purity of the Sb₂S₃ powder is not less than 99.999%; The vacuum deposition temperature is 550-550℃, the time is 60-90s, and the vacuum degree does not exceed 0.5Pa.

9. The preparation method according to claim 7, characterized in that, In the vacuum deposition, the evaporation source is 12.5 cm from the edge of the temperature zone, and the ZnO nanoarray is 2.7 cm from the edge of the temperature zone.

10. The application of a heterojunction as described in claim 1 or 2, or a heterojunction prepared by the preparation method according to any one of claims 3-9, characterized in that, Used in indoor photovoltaics, photocatalytic water splitting, photodetectors, or solar cells.

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