CN110350052B - Film structure based on copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen material perovskite heterojunction - Google Patents

Abstract

The invention provides a kesterite-oxide perovskite heterojunction structure based on a copper-zinc-tin-sulfur/bismuth iron-chromium oxide material, which belongs to the technical field of semiconductor devices. The invention discloses a method for accurately preparing a copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen heterojunction, wherein the heterojunction is obtained by in-situ deposition using a pulsed laser deposition technology. In the invention, the bismuth iron chrome oxide and the copper zinc tin sulfur are well matched to form a heterojunction structure, the advantages of the copper zinc tin sulfur material in the carrier transport are exerted, and the spontaneous electrode of the ferroelectric characteristic of the bismuth iron chrome oxide is fully utilized. It can enhance the electric field in the junction region, realize the efficient separation of electron-hole pairs, reduce their recombination, and finally improve the carrier transport efficiency. The preparation process of the copper-zinc-selenium-sulfur/bismuth-iron-chromium-oxygen heterojunction provided by the invention is accurate, strong in controllability, simple and low in cost, and the obtained heterojunction structure can be used for making relevant semiconductor functional devices, and is suitable for inorganic functional devices. The practical application of oxide perovskites is of great significance.

Description

Thin film structure based on copper-zinc-tin-sulfur/bismuth iron-chromium oxide perovskite heterojunction

technical field

The invention belongs to the technical field of semiconductor devices, and relates to a copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen heterojunction with ferroelectric properties.

Background technique

Copper-zinc-tin-sulfur (CZTS) thin films have adjustable band gaps (1.3-1.5 eV), high absorption coefficients (greater than 10 ⁴ cm ^-1 ) and good resistance to light depletion. Environmentally friendly, non-toxic and harmless, it is very suitable for the preparation of high-efficiency, stable performance and low-cost optoelectronic devices, such as absorber layers, electron transport layers, hole transport layers or photodetector materials for thin-film solar cells. In recent years, the preparation technology of copper-zinc-tin-sulfur thin films has developed rapidly, but the existing technology has problems such as high equipment and process input costs, and the preparation process will produce toxic additional products. Produce higher quality copper-zinc-tin-sulfur thin-film materials.

In recent years, electrically polarized materials with a non-centrosymmetric structure have gradually become a research hotspot, mainly because these materials have multifunctional optoelectronic properties, and the field strength of the polarized electric field is usually comparable to that of the built-in electric field of the PN junction (A. Quattropani et al., Nanoscale, 2018, 10, 13761). However, the band gap of most of these materials is larger than 2.5 eV, which limits the development and application of these materials in the fields of visible light absorption and photoelectric conversion. The inorganic oxide perovskite BiFeO ₃ (BFO) has a moderate band gap and is a typical room temperature multiferroic material. However, due to its long-range helical rotation structure, its electrical polarization at room temperature is relatively large, while its net magnetization is relatively weak. In order to improve the magnetic properties of BFO, Spaldin et al. first proposed to replace 50% of Fe ions in BFO with Cr ions through first-principles calculations to design a Bi ₂ FeCrO ₆ (BFCO) material with a double perovskite structure (P. Baettig et al., Appl.Phys.Lett., 2005, 86, 012505), mainly based on the 180° superexchange in Fe ³⁺ -O ^2– -Cr ³⁺ , which can obtain ferromagnetic order. J.Zhou et al. have confirmed through experiments that when Fe and Cr cations are alternately arranged, the magnetic properties of Bi ₂ FeCrO ₆ can reach 1.91 μ _B fu ^-1 ; on the contrary, if the two are arranged disorderly, the magnetic properties of the material are basically the same as those of pure BFO. as small (J.Zhou et al.RSC Advances, 2012, 2, 5683). In addition, by regulating the disorder degree of Fe-Cr cations in BFCO, its forbidden band width can be adjusted to 1.4 eV, corresponding to a solar cell efficiency of 3.3% based on monolayer BFCO (R.Nechache et al., Nat.Photonics, 2015, 9, 61). It can be seen that the BFCO material exhibits superior ferromagnetism and ferroelectricity (the magnetic moment and polarization can reach 2μB/fu and 80μC/cm ² , respectively, J.Miao et al., Appl.Phys.Lett., 2008, 92,062902) will have an important impact on its optoelectronic properties, and its internal mechanism, as well as the mechanism of carrier generation and migration need to be further studied; in addition, the band gap of this type of material is controllable, indicating that the inorganic oxide perovskite material is It has great potential in the field of semiconductor functional device applications.

The experimental preparation methods of copper-zinc-tin-sulfur thin films can be generally divided into vacuum methods (for example, magnetron sputtering and thermal evaporation) and non-vacuum methods (for example, solution methods such as spin coating and screen printing). The disadvantage is that the preparation process is complicated and the composition control is difficult, so that it is difficult to efficiently prepare high-quality copper-zinc-selenide-sulfur films with low defect content and dense structure. The copper-zinc-selenide-sulfur thin-film solar cell with the highest photoelectric conversion efficiency of 12.6% is prepared based on the solution method (W. Wang et al., Adv. Energy Mater., 2014, 4, 1301465), but the flatness and compactness of the film are And the ratio control of material elements has not reached the optimum, and there is still room for improvement in quality. In the experimental synthesis of BiFeCrO thin films, the initial researchers mostly used sol-gel spin coating to prepare BiFe _0.75 Cr _0.25 O ₃ (RVWilliam et al., Applied Physics A, 2018, 124, 196), BiFe _0.97 Cr _0.03 O ₃ (L .Yin et al., J.Supercond.Nov.Magn., 2014, 27, 2765) and other thin film materials, the purpose is to explore the effect of different amounts of Cr element doping based on BFO on the magnetic properties of the material; in addition, G.Kolhatkar et al. People also tried to synthesize BiFe _1-x Cr _x O ₃ by the microwave hydrothermal method, in order to apply it to the field of resistive memory (G. Kolhatkar et al., Cryst. Growth Des. 2018, 18, 1864). R. Nechache et al. prepared Bi ₂ FeCrO ₆ thin films by pulsed laser deposition (PLD) and assembled them into multilayer solar cells (R. Nechache et al., Nature Photonics, 2015, 9, 61), although the photoelectric conversion efficiency (about 8.1%) is temporarily not comparable to hybrid perovskite solar cells, but it highlights the advantages of PLD technology in the preparation of multi-component thin films. Compared with traditional thin film preparation methods, the main advantages of PLD technology mainly include: fast deposition rate; suitable for the preparation of high melting point compound material thin films; vacuum in-situ deposition can effectively prevent impurity contamination; can accurately control the composition and element distribution of multi-component compounds. ratio, and the experiment has high repeatability. The above-mentioned advantages can ensure the quality of the prepared CZTS and BFCO multicomponent compound thin films, thereby significantly improving the performance of the optoelectronic devices formed by them.

At present, although there are some reports on the application of bismuth-iron-chromium oxide semiconductor thin films to photovoltaic devices, the device structure is limited to a single-layer or multi-layer bismuth-iron-chromium oxide thin film. The material is matched with BFCO, so the advantages of its ferroelectric properties are not well exerted, and the optoelectronic properties of the device are not ideal. Therefore, further optimizing the structural design of the core part of inorganic oxide perovskite semiconductor devices and optimizing the preparation process of corresponding materials is of great significance to broaden the application scope of inorganic perovskite materials and develop new functional semiconductor devices.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide a kesterite-inorganic oxide perovskite heterojunction structure, which utilizes the heterojunction structure to achieve efficient electronic- The separation and transport of holes can solve the problems of matching the transport layer of inorganic oxide perovskite materials.

The second purpose of the present invention is to provide a preparation method suitable for multi-layer deposition of kesterite-inorganic oxide perovskite material films, so as to accurately prepare copper-zinc-selenide-sulfur/bismuth-iron-chromium by adopting a method with high controllability Oxygen heterojunction.

One of the objects of the present invention is achieved in this way:

A copper-zinc-selenium-sulfur/bismuth-iron-chromium oxide perovskite heterojunction, comprising a bismuth-iron-chromium-oxide film and a copper-zinc-selenium-sulfur film, wherein the molar ratio of each component in the bismuth-iron-chromium oxide film is Bi: Fe:Cr:O=1:1-x:x:3 (0<x<1); wherein the molar ratio of each component in the Cu:Zn:Sn:S=1.9:1.25: 1:4.15.

The second purpose of the present invention is achieved in this way:

A method for preparing a copper-zinc-selenium-sulfur/bismuth-iron-chromium-oxygen heterojunction, comprising the following steps:

(a) preparing the bismuth iron chrome oxide target material, fixing the bismuth iron chrome oxide target material on the target bracket, putting it into the deposition chamber of the pulsed laser deposition equipment, for standby;

(b) pre-processing the substrate, and then fixing it on the sample stage and placing it in the deposition chamber of the pulsed laser deposition apparatus;

(c) Under the conditions that the substrate temperature is 650-750°C and the oxygen atmosphere pressure is 0.1-10Pa, the pulsed laser deposition method is used to bombard the bismuth-iron-chromium oxide target with laser, and the thickness of the deposition on the substrate is 100～10Pa. 200nm bismuth iron chromium oxide film, after the deposition is completed, the laser is turned off for natural cooling;

(d) preparing a copper-zinc-selenium-sulfur target, fixing the copper-zinc-selenium-sulfur target on a target holder, and putting it into a deposition chamber of a pulsed laser deposition equipment for use;

(e) Under the conditions that the substrate temperature is 400-450° C. and the pressure of the argon atmosphere is 1-10 Pa, the pulsed laser deposition method is used to bombard the copper-zinc-selenium-sulfur target material with laser light, and the bismuth iron chrome obtained in step (c) is deposited On the substrate of the oxygen film, a copper-zinc-selenide-sulfur film with a thickness of 100-200 nm is continuously deposited to obtain a copper-zinc-selenide-sulfur/bismuth-iron-chromium oxide perovskite heterojunction with a thickness of 200-400 nm.

In steps (a) and (d), the bismuth-iron-chromium-oxide target and the copper-zinc-selenium-sulfur target can be purchased from the market or prepared by a solid-state powder sintering method.

The element molar ratio of the bismuth iron chromium oxide target material is Bi:Fe:Cr:O=1:1-x:x:3 (0<x<1), wherein the doping content of Cr (the range of x value) Preferably, 0.5≤x<0.9.

The element molar ratio of the copper-zinc-selenium-sulfur target material is Cu:Zn:Sn:S=1.9:1.25:1:4.15.

Preferably, the substrates in step (b) are Nb-doped SrTiO ₃ (100) single crystal substrates (abbreviated as NSTO) and Pt/Ti/SiO ₂ /Si(100) substrates (abbreviated as Pt).

In step (b), the method of pretreatment performed on the substrate is as follows: the substrate is ultrasonically cleaned in distilled water, acetone, distilled water, and isopropanol solution for 10 minutes in sequence, and then placed in a plasma cleaning machine after drying. Process for 6 minutes, set aside.

The acetone solution is acetone with a concentration of 99.5%; the isopropanol solution is an isopropanol solution with a content of 99.7%.

In steps (c) and (e), when the pulsed laser deposition method is used for deposition, the laser energy density is 1.0-2.0 J/cm ² , and the distance between the target and the substrate is 4.5 cm.

In the steps (c) and (e), when the deposition is performed by the pulsed laser deposition method, the rotation speed of the target rotation is 20 r/min, and the rotation speed of the sample stage is 10 r/min.

Before performing steps (c) and (e), the substrate is covered with a baffle plate, and the corresponding target is bombarded with a pulsed laser to perform pre-sputtering for 3-5 minutes.

In step (e), preferably after the deposition of the CZTS film, the laser is turned off, the heating temperature controller is kept at 450° C. and the pressure of the argon atmosphere is 10Pa for in-situ annealing for 40min, and then the temperature is naturally cooled to room temperature.

After performing step (e), a metal electrode is evaporated on the surface of the obtained copper-zinc-selenium-sulfur/bismuth-iron-chromium oxide perovskite heterojunction film by an electron beam evaporation method, preferably gold (Au) or platinum (Pt) )metallic material.

Applying the technical solution of the present invention, the inventor creatively couples the inorganic oxide perovskite material BFCO with the multi-component chalcogenide semiconductor compound CZTS to construct a semiconductor heterojunction structure; uses the PLD technology and in-situ deposition to prepare the CZTS/BFCO double layer Thin film, accurately control the stoichiometric ratio of elements in each layer, optimize the ratio of Cr and Fe elements in the BFCO film, so that CZTS and BFCO are well matched, so as to give full play to the ferroelectric properties of BFCO, and make full use of the CZTS film in terms of carrier transport. Advantages, forming a heterojunction structure to achieve efficient electron-hole pair separation, reducing the recombination between them, and ultimately improving the carrier transport efficiency.

The invention adopts pulse laser deposition technology and in-situ deposition to prepare a kesterite-perovskite heterojunction. Compared with the films prepared by conventional solution methods such as conventional spin coating methods, the morphology of the films obtained by the invention is more uniform and dense, the control of the stoichiometric ratio of the multi-element elements contained in each film material is more precise and efficient, and it is easy to control the deposition. Obtaining films with different thicknesses over time is beneficial to improve the quality of the prepared films, thereby efficiently improving the comprehensive performance of the heterojunction.

The copper-zinc-selenium-sulfur/bismuth-iron-chromium-oxygen heterojunction disclosed by the invention has high process precision, strong controllability, simple method and low production cost, and the obtained heterojunction structure can be used in the fields of photovoltaic power generation, photocatalysis and other related fields. Semiconductor functional devices have broad application prospects and are of great significance to the industrialization and practical application of oxide perovskites.

The advantages, features and meanings of the present invention will be more clearly understood by those skilled in the art according to the following description of the drawings and the detailed description of the present invention in combination with specific implementation method examples.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic diagram of the structure of the CZTS/BFCO/Pt heterojunction prepared in Example 1.

FIG. 2 is a schematic diagram of the energy band structure of the CZTS/BFCO heterojunction prepared in Example 1. FIG.

FIG. 3 is a current-voltage (j-V) test curve of the CZTS/BFCO/Pt heterojunction prepared in Example 1. FIG.

4 is a graph of X-ray diffraction test data of the BFCO thin film prepared in Comparative Example 1.

5 is a graph of scanning electron microscope test data of the BFCO thin film prepared in Comparative Example 1.

FIG. 6 is an atomic force microscope test data graph of the BFCO thin film prepared in Comparative Example 1. FIG.

7 is a graph of X-ray diffraction test data of the CZTS thin film prepared in Comparative Example 2.

8 is a graph of scanning electron microscope test data of the CZTS thin film prepared in Comparative Example 2.

FIG. 9 is an atomic force microscope test data graph of the CZTS thin film prepared in Comparative Example 2. FIG.

Detailed ways

In order to make the purpose, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The present invention will be further elaborated below in conjunction with the examples. The following examples are only for illustration and do not limit the present invention in any way.

The reagents used in the examples are all analytically pure or chemically pure, and can be purchased from the market or prepared by methods well known to those of ordinary skill in the art. The following embodiments all achieve the purpose of the present invention.

Example 1

As shown in Fig. 1, a copper-zinc-selenide-sulfur/bismuth _- iron-chromium-oxide perovskite heterojunction includes bismuth-iron-chromium-oxide and Copper-zinc-selenium-sulfur bilayer films.

The concrete technological process that this example prepares this heterojunction is:

The bismuth iron chromium oxide target with the element molar ratio of Bi:Fe:Cr:O=1:0.5:0.5:3 is selected, and the copper zinc with the element molar ratio Cu:Zn:Sn:S=1.9:1.25:1:4.15 is selected. Selenium sulfur target.

The substrates were ultrasonically cleaned in distilled water, 99.5% acetone, distilled water, and 99.7% isopropanol solution in sequence for 10 minutes each, dried and placed in a plasma cleaning machine for 6 minutes for use.

The bismuth iron chrome oxide target is fixed on the target bracket and placed in the deposition chamber of the pulsed laser deposition equipment for standby use; the pretreated Pt substrate is fixed on the sample stage and placed in the deposition chamber of the pulsed laser deposition equipment The distance between the target and the substrate is 4.5cm, the deposition temperature is preferably 650°C, and the oxygen atmosphere pressure is preferably 0.2Pa, the laser energy density used is preferably 2J/cm ² , and the target rotates The rotation speed of the sample stage is 20r/min, and the rotation speed of the sample stage is 10r/min. First, cover the substrate with a baffle, bombard the BiFeCrO target with a pulsed laser for 5 minutes, and then remove the baffle, continue to bombard the BiFeCrO target with a pulsed laser, and deposit on the Pt substrate with a thickness of 100nm bismuth iron chrome oxide film. After the deposition was completed, the laser was turned off for natural cooling.

Fix the copper-zinc-selenium-sulfur target on the target holder and put it into the deposition chamber of the pulsed laser deposition equipment for use. Under the conditions that the deposition temperature is preferably 450°C and the pressure of the argon atmosphere is preferably 10Pa, the laser energy density used is preferably 2J/cm ² , the rotation speed of the target rotation is 20r/min, and the rotation speed of the sample stage is 10r/min . First, cover the substrate with a baffle, bombard the CuZnSeS target with a pulsed laser for 5 min for pre-sputtering; then remove the baffle, continue to bombard the CuZnSeS target with a pulsed laser, on the obtained BFCO/Pt A CuZnSeS thin film was deposited with a thickness of 100nm. Preferably, after the deposition is completed, the laser is turned off, the heating temperature controller is maintained at 450°C, the pressure of the argon atmosphere is 10Pa, and the in-situ annealing is performed for 40min, and then the temperature is naturally cooled to room temperature to obtain copper-zinc-selenium-sulfur/bismuth with a thickness of about 200nm. Iron chromium oxide perovskite heterojunction (abbreviated as CZTS/BFCO/Pt).

On the surface of the obtained copper-zinc-selenium-sulfur/bismuth iron chromium oxide perovskite heterojunction thin film, a Pt metal electrode is evaporated by an electron beam evaporation method, which is convenient for electrical testing. The schematic diagram of its structure is shown in Figure 1.

2 is a schematic diagram of the energy band structure of the CZTS/BFCO oxide perovskite heterojunction prepared in Example 1. In addition to the built-in electric field generated by the semiconductor heterojunction itself, the spontaneous polarization mechanism of the bismuth-iron-chromium oxide ferroelectric thin film can enhance the electric field in the junction area. If it is used in the field of visible light absorption and conversion, it can more effectively separate photogenerated electrons -Hole pairs, reducing the recombination of electrons and holes, thereby improving the carrier transport efficiency.

The obtained j-V test curve of the CZTS/BFCO/Pt oxide perovskite heterojunction is shown in Figure 3. It can be seen that the current density is in the order of milliamps and has good rectification characteristics.

Comparative Example 1

The bismuth iron chromium oxide target with the element molar ratio of Bi:Fe:Cr:O=1:0.5:0.5:3 is selected.

The NSTO substrates were ultrasonically cleaned in distilled water, 99.5% acetone, distilled water, and 99.7% isopropanol solution for 10 minutes each in sequence, and then placed in a plasma cleaner for 6 minutes after drying. The pretreated NSTO substrate was fixed on the sample stage and placed in the deposition chamber of the pulsed laser deposition equipment for use; the distance between the target and the substrate was 4.5 cm, the deposition temperature was set to 650 °C, and the oxygen atmosphere pressure was 0.2Pa, the laser energy density used is 2J/cm ² , the target rotation speed is 20r/min, and the sample stage rotation speed is 10r/min. First cover the substrate with a baffle, bombard the bismuth-iron-chromium oxide target with a pulsed laser for 5 minutes for pre-sputtering; then remove the baffle, continue to bombard the bismuth-iron-chrome oxide target with a pulsed laser, and deposit a thickness of about 50% on the NSTO substrate. It is a 100nm bismuth iron chromium oxide film. After the deposition is completed, the laser is turned off for natural cooling.

The X-ray diffraction data of the obtained sample is shown in Fig. 4, which shows that the BFCO film is epitaxially grown along the crystal phase of the substrate, and the crystallinity of the film is good.

The material morphology of the obtained BFCO film was characterized. It can be seen from the scanning electron microscope image in FIG. 5 and the atomic force microscope image in FIG. 6 that the obtained BFCO film is basically dense and uniform.

Comparative Example 2

A copper-zinc-selenium-sulfur target with an element molar ratio of Cu:Zn:Sn:S=1.9:1.25:1:4.15 was selected.

The FTO conductive glass substrates were ultrasonically cleaned in distilled water, 99.5% acetone, distilled water, and 99.7% isopropanol solution for 10 minutes in sequence, and then placed in a plasma cleaner for 6 minutes after drying.

Fix the copper-zinc-selenium-sulfur target on the target holder and put it into the deposition chamber of the pulsed laser deposition equipment for use. The distance between the target and the substrate is 4.5cm, the deposition temperature is set to 450°C, the pressure of the argon atmosphere is 10Pa, the laser energy density used is 2J/cm ² , the rotation speed of the target is 20r/min, and the sample stage is The rotation speed is 10r/min. First, cover the substrate with a baffle, bombard the copper-zinc-selenide-sulfur target with a pulsed laser for 5 minutes for pre-sputtering; then remove the baffle, continue to bombard the copper-zinc-selenide-sulfur target with a pulsed laser, and deposit on the obtained FTO substrate A copper-zinc-selenide-sulfur film with a thickness of about 100 nm. After the deposition is completed, the laser is turned off, the heating temperature controller is maintained at 450°C, and the pressure of the argon atmosphere is 10Pa for in-situ annealing for 40min, and then waits for natural cooling to room temperature.

The X-ray diffraction data chart of the obtained sample is shown in FIG. 7 , which shows that the crystallinity of the CZTS film is good.

The material morphology of the obtained CZTS film was characterized. It can be seen from the scanning electron microscope image in FIG. 8 and the atomic force microscope image in FIG. 9 that the obtained CZTS film is basically dense and uniform.

Claims (5)

1. The thin film structure based on the copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen material perovskite heterojunction is characterized by comprising a bismuth-iron-chromium-oxygen thin film and a copper-zinc-selenium-sulfur thin film, wherein the molar ratio of the components in the bismuth-iron-chromium-oxygen thin film is Bi: Fe: Cr: O (1: 1-x: x: 3) (0< x <1), and the molar ratio of the components in the copper-zinc-selenium-sulfur thin film is Cu: Zn: Sn: S (1.9: 1.25:1: 4.15).

2. The preparation method of the thin film structure based on the perovskite heterojunction of the copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen material as claimed in claim 1, characterized by comprising the following steps:

(a) preparing a bismuth iron chromium oxygen target material, and fixing the bismuth iron chromium oxygen target material on a target support of a deposition cabin of pulsed laser deposition equipment for later use;

(b) preprocessing a substrate, and then fixing the substrate on a sample table of a deposition cabin of pulse laser deposition equipment for later use;

(c) bombarding the bismuth iron chromium oxygen target material by laser, and depositing a bismuth iron chromium oxygen film on the substrate;

(d) preparing a copper-zinc-selenium-sulfur target material, and fixing the copper-zinc-selenium-sulfur target material on a target support of a deposition cabin of pulsed laser deposition equipment for later use;

(e) bombarding the copper zinc selenium sulfur target material by laser, and continuously depositing a layer of copper zinc selenium sulfur film on the substrate deposited with the bismuth iron chromium oxygen film obtained in the step (c), so as to obtain the copper zinc selenium sulfur/bismuth iron chromium oxygen oxide perovskite heterojunction.

3. The method for preparing the thin film structure based on the perovskite heterojunction of the CuZnSn-S/Bi-Fe-Cr-O material as claimed in claim 2, wherein the deposition temperature in the step (c) is 650-750 ℃, and the pressure of oxygen atmosphere is 0.1-10 Pa.

4. The method for preparing the thin film structure based on the perovskite heterojunction of the CuZnSn-S/Bi-Fe-Cr-O material as claimed in claim 2, wherein in the step (e), the deposition temperature is 400-450 ℃, and the argon atmosphere pressure is 1-10 Pa.

5. The method for preparing a thin film structure based on a copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen material perovskite heterojunction as claimed in claim 2, wherein in the step (e), preferably after the deposition of the copper-zinc-tin-sulfur/bismuth-iron-chromium-oxygen material perovskite heterojunction is completed, the heating temperature controller is heated to maintain 450 ℃ and the argon atmosphere pressure is 10Pa, and in-situ annealing is carried out for 40min, and then natural cooling is carried out until the temperature is reduced to room temperature.

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