CN107364836B - Tin-germanium-sulfur selenide thin film, preparation method thereof and photoelectric conversion device - Google Patents

Abstract

The invention prepares the high-quality tin-germanium-sulfur selenide film by simultaneously increasing the Ge content and the sulfur-selenium partial pressure, wherein the Ge content is tin-germanium-sulfur selenide (M1)_x1M2_x2Sn_1‑xGe_xS_1‑ySe_y) (M1 is one or two of Cu and Ag mixed at any ratio, M2 is one or two of Zn and Cd mixed at any ratio, x is more than or equal to 0₁≤1，0≤x₂≤1，0<x is less than or equal to 1, y is less than or equal to 0 and less than or equal to 1), the relative proportion of Ge and Sn (Ge/(Ge + Sn)), and the sulfur-selenium partial pressure is simple substance S steam, simple substance Se steam and H in the sulfur-selenization treatment process₂S gas or H₂Partial pressure of Se gas. The photoelectric performance of the tin germanium sulfide selenide thin film is greatly improved by simultaneously increasing the Ge content and the sulfur selenium partial pressure, the method is simple to operate and has universality, and the prepared high-quality tin germanium sulfide selenide thin film can be applied to photoelectric devices such as solar cells, photolysis water cells, photoelectric detectors and the like.

Description

Tin-germanium-sulfur-selenide film and preparation method thereof, and photoelectric conversion device

technical field

The invention belongs to the technical field of optoelectronic materials, and particularly relates to a tin-germanium-sulfur-selenide film, a preparation method thereof, and a photoelectric conversion device.

Background technique

With the continuous improvement of the industrialization level of human society, the total energy demand of society continues to increase. According to data provided by the U.S. Department of Energy's 2017 Annual Energy Report, the world's average energy consumption is about 14TW. Among them, the consumption of fossil energy such as oil, natural gas and coal accounts for about 85% of the total energy consumption of human society. In the short term, the main problem facing human society is not the shortage of fossil energy reserves, but the greenhouse effect caused by the massive consumption of fossil energy. Studies have shown that if all the fossil energy on the earth is consumed, the carbon dioxide content in the earth's atmosphere and ocean will reach the value before the appearance of early humans on the earth. In order to prevent the harm caused by the greenhouse effect, it is a very urgent task to develop and utilize the abundant solar energy resources on the earth. Although solar energy has the advantages of abundant total, renewable, and clean, its disadvantages of low energy density and discontinuous energy transmission limit its large-scale practical application. Therefore, how to easily and economically capture and store solar energy is still a difficult problem for large-scale utilization of solar energy.

Thin-film solar photovoltaic cells and water-splitting cells are two promising technologies that can utilize solar energy on a large scale. Multi-element sulfur selenides, such as Cu ₂ ZnSn(SSe) ₄ (CZTSSe), have the advantages of suitable band gap and high light absorption coefficient (>10 ⁴ cm ^-1 ), which are used as light absorption materials in solar photovoltaic cells and water splitting cells. and other fields have received extensive attention. However, CZTSSe (copper-zinc-tin-sulfur-selenide compound) contains deep-level defects related to divalent tin, which limits the improvement of photovoltage.

SUMMARY OF THE INVENTION

In the conventional process of preparing CZTSSe by the solution-spin coating-sulfurization method, the Ge content is usually 0, and the sulfur-selenium partial pressure (that is, the thin film during the sulfur-selenization process (including sulfurization, selenization or sulfur-selenization) is usually 0. The vapor pressure of sulfur element or hydrogen sulfide, selenium element or hydrogen selenide above the sample is 0.03 atm or even lower, the thin film sample prepared in this way cannot meet the requirements of large grain size and pure phase at the same time, which greatly limits its optoelectronic properties. The object of the present invention is to provide a method for improving the solar energy conversion efficiency of a tin-germanium-sulfur-selenide solar cell or a water-splitting cell, that is, in the preparation process of the solution-spin coating-sulfurization method, by simultaneously increasing the content of germanium and the content of sulfur and selenium The method of pressing to obtain a tin-germanium-sulfur-selenide film with a large grain size and a pure phase, so as to achieve a substantial improvement in the solar energy conversion efficiency of photoelectric conversion devices using the film as a light absorbing material

The invention discloses a tin-germanium-sulfur-selenide film. The chemical formula of the tin-germanium-sulfur-selenide film is M1 _x1 M2 _x2 Sn _1-x Ge _x S _1-y Se _y , wherein M1 is the metal element Cu, One or two mixtures of Ag in arbitrary proportions, M2 is one or two mixtures of metal elements Zn and Cd in arbitrary proportions, 0≤x ₁ ≤1, 0≤x ₂ ≤1, 0<x≤1, 0≤y≤1, the tin-germanium-sulfur-selenide film is prepared by a solution-spin coating-sulfurization method, and during the sulfur-selenide treatment, the following conditions are met: if 0<x<0.1, the partial pressure of sulfur-selenium is 0.05-2 atmospheres; If 0.1≤x≤0.4, the partial pressure of sulfur and selenium is 0.2-5 atmospheres; if 0.40<x≤1, the partial pressure of sulfur and selenium is 0.5-5 atmospheres.

As a preferred solution, if 0<x<0.1, the partial pressure of sulfur and selenium is 0.05-1 atmosphere; if 0.1≤x≤0.4, the partial pressure of sulfur and selenium is 0.2-2 atmosphere; if 0.40<x≤1, the sulfur Selenium partial pressure is 1-3 atmospheres.

The invention also discloses a tin-germanium-sulfur-selenide film. The chemical formula of the tin-germanium-sulfur-selenide film is M1 _x1 M2 _x2 Sn _1-x Ge _x S _1-y Se _y , wherein M1 is the metal element Cu , one or two mixtures in arbitrary proportions of Ag, M2 is one or two mixtures in arbitrary proportions of metal elements Zn and Cd, 0≤x ₁ ≤1, 0≤x ₂ ≤1, 0.1≤x≤0.4 , 0≤y≤1, the tin-germanium-sulfur-selenide film is prepared by a solution-spin coating-sulfurization method, and the partial pressure of sulfur and selenium is 0.2-2 atmospheres during the sulfur selenization treatment.

The invention also discloses a photoelectric conversion device, which adopts the tin-germanium-sulfur-selenide film with the features disclosed in the above scheme as the light absorbing material.

The invention also discloses a preparation method of a tin-germanium sulfide-selenide film, which is characterized in that the chemical formula of the tin-germanium sulfide-selenide film is M1 _x1 M2 _x2 Sn _1-x Ge _x S _1-y Se _y , Wherein, M1 is a mixture of one or two of metal elements Cu and Ag in arbitrary proportion, M2 is a mixture of one or two of metal elements Zn and Cd in arbitrary proportion, 0≤x ₁ ≤1, 0≤x ₂ ≤ 1, 0<x≤1, 0≤y≤1, using a solution-spin coating-sulfurization method to prepare a tin-germanium-sulfur-selenide film, including the following steps:

Step 1, prepare a precursor solution: a mixture in any proportion of one or more of the nitrate, acetate, chloride, bromide or iodide salts containing M1 and M2 metal ions, a tin source, The germanium source and thioselenourea are respectively added to one or more mixed solvents in any ratio of ethylene glycol methyl ether, dimethyl sulfoxide, methanol, ethanol or ethylene glycol to be stirred and mixed to obtain a clear precursor body solution;

Step 2, spin coating and calcination: aging the clarified precursor solution obtained in step 1; spin coating the aged precursor solution on the conductive substrate and calcining to obtain a precursor sample film; repeat the above spinning process. coating and calcination process to obtain the desired thickness of the precursor sample film;

Step 3, sulfur selenization: subjecting the precursor sample film obtained in step 2 to sulfur selenization treatment, and after the treatment is completed, the target tin germanium sulfur selenide film is obtained;

During the preparation of the precursor solution, the content of germanium, that is, the value of x, is controlled by adjusting the relative ratio of the tin source and the germanium source; in the case of sulfur selenization treatment: if 0<x<0.1, the partial pressure of sulfur and selenide is 0.05-2 Atmospheric pressure; if 0.1≤x≤0.4, the partial pressure of sulfur and selenium is 0.2-5 atmospheres; if 0.40<x≤1, the partial pressure of sulfur and selenium is 0.5-5 atmospheres.

As a preferred solution, if 0<x<0.1, the partial pressure of sulfur and selenium is 0.05-1 atmosphere; if 0.1≤x≤0.4, the partial pressure of sulfur and selenium is 0.2-2 atmosphere; if 0.40<x≤1, the sulfur Selenium partial pressure is 1-3 atmospheres.

As a preferred solution, 0.1≤x≤0.4, and the partial pressure of sulfur and selenium is 0.2-2 atmospheres during the sulfur selenization treatment.

As a preferred solution, in step 1, the tin source is one or a mixture of any ratio of two or more in acetate, chloride, bromide or iodide containing Sn ²⁺ and Sn ⁴⁺ ions ; The germanium source is a mixture of one or two or more arbitrary proportions in germanium chloride, germanium bromide or germanium iodide; the solvent is ethylene glycol methyl ether, dimethyl sulfoxide, methanol, ethanol and ethylene glycol A mixture of one or more than two in any proportion.

As a preferred solution, in step 3, the precursor sample film obtained in step 2 is placed in one or a combination of elemental sulfur vapor, elemental selenium vapor, hydrogen sulfide gas, hydrogen selenide gas, or a combination thereof for sulfur selenization treatment .

As a preferred solution, in step 3, the precursor sample film and germanium sulfide selenide obtained in step 2 are subjected to sulfide selenization treatment, and the germanium content is controlled by adjusting the quality of germanium sulfide selenide. The sulfide selenide of germanium is one of germanium sulfide, germanium sulfide, germanium selenide, and germanium selenide, or a mixture of two or more of them in any proportion.

As a preferred solution, in step 2, aging for 0-200 hours in an environment with a relative humidity of 5%-95%, and calcining in air at 200-550°C for 1-60 minutes; in step 3, at 450-600 The sulfur selenization is carried out at a temperature of ℃, and the sulfur selenization time is 20-120 minutes.

As a preferred solution, the thickness of the tin-germanium-sulfur-selenide film obtained after the sulfur selenization is completed is 0.05-5 microns. Such as 0.05-3 microns.

As a preferred solution, the device for sulfide-selenization treatment of the precursor sample film in step 3 is an open type, and the open-type device is a quartz tube heated by a tube furnace with ventilation at both ends. The flow rate of the medium carrier gas is adjusted within the range of 10mL/min-1000mL/min, and the heating temperature is adjusted within the range of 400°C-700°C.

As a preferred solution, the device for sulfide selenization treatment of the precursor sample film in step 3 is a sealed device, and the sealed device is a quartz tube heated by a tube furnace with valves at both ends. When sulfur selenization is performed, the quartz The valves at both ends of the tube are closed, the inert gas and the source of sulfur and selenium are sealed in the quartz tube, and the heating temperature is adjusted within 400℃-700℃.

The present invention has the following beneficial effects:

(1) Based on the conventional solution-spin coating-sulfurization method, a large grain size and pure phase tin-germanium-sulfelenide film was prepared by simultaneously increasing the solid solution content of germanium and the partial pressure of sulfur-selenium. The optoelectronic properties of the thin film are greatly improved, and the present invention also provides a ten-fold improvement in a preferred embodiment.

(2) The tin-germanium-sulfur-selenide film disclosed in the present invention can be used as a light absorbing material in solar energy conversion devices, such as photovoltaic cells, photo-splitting water cells and photodetectors, etc., to improve the tin-germanium sulfur selenide solar cells or Photovoltaic water splitting cell solar energy conversion efficiency.

(3) The method is improved based on the existing solution-spin coating-vulcanization method, and has the advantages of simple operation, low cost and easy mass production.

Description of drawings

1 is a SEM image of the surface and cross-section of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 1 of the present invention. (a) and (c) are the surface and cross-sectional SEM images of the CZTS film prepared in Comparative Example 1; (b) and (d) are the surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 1.

2 is the XRD patterns of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 1 of the present invention.

3 is the Raman spectrum of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 1 of the present invention. (a) is the visible Raman spectrum, (b) is the ultraviolet Raman spectrum.

4 is a photocurrent-potential curve diagram of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 1 after CdS/In ₂ S ₃ /Pt is supported.

5 is the surface and cross-sectional SEM images of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 2. (a) and (c) are the surface and cross-sectional SEM images of the CZTS film prepared in Comparative Example 1; (b) and (d) are the surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 2.

6 is a photocurrent-potential graph of the CZTS/CdS/In _{2 S 3 /Pt photocathode prepared in Comparative Example 1 and the Ge-CZTS/CdS/In 2 S 3 / Pt} photocathode prepared in Example 2.

7 is the surface and cross-sectional SEM images of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 3. (a) and (c) are the surface and cross-sectional SEM images of the CZTS film prepared in Comparative Example 1; (b) and (d) are the surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 2.

8 is a photocurrent-potential graph of the CZTS/CdS/In _{2 S 3 /Pt photocathode prepared in Comparative Example 1 and the Ge-CZTS/CdS/In 2 S 3 / Pt} photocathode prepared in Example 3.

9 is the surface and cross-sectional SEM images of the CZTS thin film prepared in Comparative Example 1 and the Ge-CZTS thin film prepared in Example 4. (a) and (c) are the surface and cross-sectional SEM images of the CZTS film prepared in Comparative Example 1; (b) and (d) are the surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 2.

10 is a photocurrent-potential graph of the CZTS/CdS/In _{2 S 3 /Pt photocathode prepared in Comparative Example 1 and the Ge-CZTS/CdS/In 2 S 3 / Pt} photocathode prepared in Example 4.

Detailed ways

The tin-germanium-sulfur-selenide film can be prepared by a solution-spin coating-sulfurization method, and the specific steps are:

Step 1. Prepare the precursor solution:

In the multi-element sulfur selenide, one or more arbitrary proportion mixtures in nitrate, acetate, chloride, bromide or iodide salt containing M1 and M2 metal ions, containing Sn ²⁺ and Sn ⁴⁺ ion acetate, chloride salt, bromide salt or iodide salt in one or more arbitrary proportion mixture (i.e. tin source), in germanium chloride, germanium bromide or germanium iodide One or two or more mixtures in arbitrary proportions (ie, germanium source), and thioselenourea are respectively added to the solvent for stirring and mixing to obtain a clear precursor solution. The solvent is selected from one of ethylene glycol methyl ether, dimethyl sulfoxide, methanol, ethanol and ethylene glycol or a mixture of two or more in any ratio.

Wherein, the tin source in the precursor solution is any ratio mixture of one or more of the acetate, chloride, bromide or iodide salts containing Sn ²⁺ and Sn ⁴⁺ ions; germanium salt It is one of germanium chloride, germanium bromide or germanium iodide or a mixture of two or more in any proportion; the solvent is one of ethylene glycol methyl ether, dimethyl sulfoxide, methanol, ethanol and ethylene glycol or A mixture of two or more in any ratio. The types of germanium sources in the precursor solution include: germanium tetrachloride, germanium tetrabromide, germanium tetraiodide, germanium diiodide, germanium dioxide, and one or more of them can be used in any ratio when configuring the solution mix. The content of Ge in the tin-germanium sulphide selenide can be adjusted by adjusting the relative ratio of germanium source and tin source in the precursor.

Step 2. Spin coating and calcination

The clear precursor solution prepared in step 1 is aged for 0-200 hours in an environment with a relative humidity of 5%-95% to obtain an aged precursor solution.

The aged precursor solution is spin-coated on the conductive substrate, and calcined in air at 200-550° C. for 1-60 minutes to obtain a precursor sample film.

The above spin coating and calcination steps are repeated to obtain a precursor sample film with a certain thickness, and the thickness needs to be optimized according to the optoelectronic properties of the tin-germanium-sulfur-selenide film.

Step three, sulfur selenization treatment

After the spin coating and calcination are completed, the precursor sample film is subjected to sulfur selenization at a temperature of 450-600 ℃, and the sulfur selenization time is 20-120 minutes. The sulfur selenization can be carried out in elemental sulfur vapor, elemental selenium vapor or hydrogen sulfide. , in hydrogen selenide gas.

The types of germanium sulfide selenides in the sulfide selenization step include germanium sulfide, germanium sulfide, germanium selenide, germanium selenide. In the sulfur selenization step, one or more of them can be mixed in any ratio.

In the above method, the tin-germanium-sulfur-selenide film with large grain size and pure phase can be obtained by simultaneously increasing the solid solution content of germanium and the partial pressure of sulfur.

By adjusting the quality of elemental sulfur, elemental selenium or hydrogen sulfide used in the sulfur selenization process, the gas pressure of hydrogen selenide gas can control the partial pressure of sulfur and selenium. After the sulfur selenization is completed, a tin germanium sulfur selenide film with a thickness of about 0.05-5 microns is obtained, and the thickness of the film can be adjusted according to the needs of the corresponding photoelectric conversion device, such as 0.05-3 microns. In the preparation process, the tin-germanium-sulfur-selenide thin film with large grain size and pure phase can be obtained by simultaneously increasing the germanium content and the partial pressure of sulfur-selenium during the sulfur-selenization process. The content of Ge can be adjusted by adjusting the relative ratio of tin source and germanium source in the precursor solution and by adjusting the quality of germanium sulfide selenide in the sulfide selenization step. In this method, the devices for sulfide selenization treatment of tin germanium sulfide selenide are divided into two types: open type and sealed type. The effect of using the sealed type device is the same as that of the open type device, but the sealed type device can save time in the sulfur selenization process. The amount of sulfur and selenium source.

The open device is a quartz tube heated by a tube furnace with ventilation at both ends. When sulfur selenization is performed, the flow rate of the carrier gas in the quartz tube can be adjusted in the range of 10ml/min-1000ml/min, and the heating temperature can be 400 ℃ Adjust within -700°C.

The sealed device is a quartz tube heated by a tube furnace with valves at both ends. When sulfur selenization is performed, the valves at both ends of the quartz tube are closed, and the inert gas and sulfur and selenium sources are sealed in the quartz tube. The heating temperature can be 400℃- Adjust within 700°C. The sealed device can also be replaced by a sealed quartz glass test tube filled with an inert gas and containing a sulfur-selenium source and a sample. For sulfur-selenide, the sealed quartz glass test tube can be heated in a tube furnace.

For different types of sulfur-selenide treatment devices, the methods of increasing the partial pressure of sulfur-selenide in the sulfur-selenization step include: increasing the mass of S powder or Se powder used in the open-type sulfur-selenization device, H ₂ S or H ₂ Se gas flow rate; increase the quality of S powder or Se powder used in the sealed sulfur selenization device. In the open sulfide selenization treatment device, the normal direction of the precursor sample film can be adjusted between 0° and 360° relative to the direction of the carrier gas flow in the open device to obtain different sulfide selenization effects. For example, for an open device, when x>0.25, mS>12/2600g/cm ³ (ie, 12g of _sulfur element per 2600cm ³ device volume) can be selected.

Below in conjunction with specific embodiment, the present invention will be further described:

Comparative Example 1:

Step 1. Dissolve 1.5224g thioselenourea, 0.4513g SnCl ₂ ·2H ₂ O, 0.7187g Cu(CH ₃ COO) ₂ ·H ₂ O and 0.3271g ZnCl ₂ into 20ml of ethylene glycol methyl ether solution in turn, and fully Stir to configure a clear precursor solution.

Step 2. The clarified precursor solution is placed in air at 20° C. and 70% humidity for 3 hours for aging to prepare an aged precursor solution. The aged precursor solution was prepared into a precursor sample thin film on a molybdenum glass substrate by spin coating. The spin coating speed was 3000 rpm for 30 seconds. Each spin-coated layer was calcined in air at 400°C for 5 minutes. To obtain optimal film thickness, spin coating was repeated 5 times.

Step 3. After the spin coating is completed, an open device is used, and 0.5 g of sulfur powder is used as the sulfur source, and the solution is vulcanized under a nitrogen atmosphere at 580° C. for 60 minutes. During vulcanization, nitrogen with a flow rate of 100 ml min ^-1 was used as the carrier gas. After the vulcanization is completed, a 1.2 μm thick CZTS (copper zinc tin sulfur) film (that is, a kind of tin germanium sulfur selenide film) is obtained.

Example 1:

Step 1. Combine 1.5224g thioselenourea, 0.0872g CuCl, 0.1504g Zn(Ac) ₂ , 0.2338g ZnCl ₂ , 0.1072g GeCl ₄ , 0.3384g SnCl ₂ ·2H ₂ O and 0.527g Cu(CH ₃ COO) ₂ ·H ₂ O was sequentially dissolved in 20 ml of ethylene glycol methyl ether solution, and stirred well to prepare a clear precursor solution (x=0.25).

Step 2. The clarified precursor solution is placed in air at 20° C. and 70% humidity for 6 hours for aging to prepare an aged precursor solution. The aged precursor solution was prepared into a precursor sample thin film on a molybdenum glass substrate by spin coating. The spin coating speed was 1500 rpm for 30 seconds. Each spin-coated layer was calcined in air at 400°C for 5 minutes. To obtain optimal film thickness, spin coating was repeated 11 times.

Step 3. After the spin coating is completed, an open device is used, and 12 grams of sulfur powder is used as the sulfur source to control the sulfur bias pressure to be 0.5 atmospheres, (10 grams of sulfur powder more than the comparative example, and the partial pressure of sulfur and selenium is increased), in Vulcanized under nitrogen atmosphere at 580°C for 60 minutes. During vulcanization, nitrogen with a flow rate of 100 mL min ^-1 was used as the carrier gas. After the vulcanization is completed, a 1.2 μm thick Ge-CZTS (copper zinc tin germanium sulfur) film (that is, a kind of tin germanium sulfur selenide film) is obtained.

Example 2:

Step 1. Combine 1.5224g thioselenourea, 0.0872g CuCl, 0.123g Zn(Ac) ₂ , 0.2508g ZnCl ₂ , 0.0429g GeCl ₄ , 0.4062g SnCl ₂ ·2H ₂ O and 0.527g Cu(CH ₃ COO) ₂ ·H ₂ O was successively dissolved in 20 mL of ethylene glycol methyl ether solution, and stirred well to prepare a clear precursor solution (x=0.1).

Step 2. The clarified precursor solution is aged in air at 20° C. and 70% humidity for 4 hours to prepare an aged precursor solution. The aged precursor solution was prepared into a precursor sample thin film on a molybdenum glass substrate by spin coating. The spin coating speed was 1500 rpm for 30 seconds. Each spin-coated layer was calcined in air at 400°C for 5 minutes. To obtain optimal film thickness, spin coating was repeated 8 times.

Step 3. After the spin coating is completed, an open device is used, and 12 grams of sulfur powder is used as the sulfur source, and the solution is vulcanized under a nitrogen atmosphere at 580° C. for 60 minutes. During vulcanization, nitrogen with a flow rate of 100 mL min ^-1 was used as the carrier gas. After vulcanization, a 1.2 μm thick Ge-CZTS film was obtained.

Example 3:

Step 1. Combine 1.5224g thioselenourea, 0.1504g CuCl, 0.289g Zn(Ac) ₂ , 0.1478g ZnCl ₂ , 0.1715g GeCl ₄ , 0.2708g SnCl ₂ ·2H ₂ O and 0.3994g Cu(CH ₃ COO) ₂ ·H ₂ O was successively dissolved in 20 mL of ethylene glycol methyl ether solution, and stirred well to prepare a clear precursor solution (x=0.4).

Step 2. The clarified precursor solution is placed in air at 20° C. and 70% humidity for 8 hours for aging to prepare an aged precursor solution. The aged precursor solution was prepared into a precursor sample thin film on a molybdenum glass substrate by spin coating. The spin coating speed was 1500 rpm for 30 seconds. Each spin-coated layer was calcined in air at 400°C for 5 minutes. To obtain optimal film thickness, spin coating was repeated 14 times.

Step 3. After the spin coating is completed, an open device is used, and 12 grams of sulfur powder is used as the sulfur source, and the solution is vulcanized under a nitrogen atmosphere at 580° C. for 60 minutes. During vulcanization, nitrogen with a flow rate of 100 ml min ^-1 was used as the carrier gas. After vulcanization, a 1.2 μm thick Ge-CZTS film was obtained.

Example 4:

Step 1. Combine 1.5224g thioselenourea, 0.0872g CuCl, 0.1504g Zn(Ac) ₂ , 0.2338g ZnCl ₂ , 0.1072g GeCl 4 , 0.3384g SnCl ₂ ·2H ₂ O and 0.527g Cu(CH ₃ COO) ₂ · H ₂ O was successively dissolved in 20 mL of ethylene glycol methyl ether solution, and stirred well to prepare a clear precursor solution (x=0.25).

Step 2. The clarified precursor solution is placed in air at 20° C. and 70% humidity for 6 hours for aging to prepare an aged precursor solution. The aged precursor solution was prepared into a precursor sample thin film on a molybdenum glass substrate by spin coating. The spin coating speed was 1500 rpm for 30 seconds. Each spin-coated layer was calcined in air at 400°C for 5 minutes. To obtain optimal film thickness, spin coating was repeated 11 times.

Step 3. After the spin coating is completed, an open device is used, and 0.5 g of sulfur powder is used as the sulfur source, and the solution is vulcanized under a nitrogen atmosphere at 580° C. for 60 minutes. During vulcanization, nitrogen with a flow rate of 100 mL min ^-1 was used as the carrier gas. After vulcanization, a 1.2 μm thick Ge-CZTS film was obtained.

Before carrying out the photocurrent-potential curve test on the tin-germanium-sulfur-selenide thin film samples of Comparative Example 1 and Examples 1-3, they need to be surface-modified, and the steps are as follows:

First, 5ml of CdSO ₄ aqueous solution with a concentration of 0.015mol/L, 6.5ml of concentrated ammonia water (28-30%) was added to 36mL of deionized water and stirred for 5 minutes, then 2.5mL of 1.5mol/L thiourea aqueous solution was added in the above solution. After the tin-germanium-sulfur-selenide film was immersed in the solution, the reaction solution was heated in a water bath, and the reaction time was 5 minutes. After the reaction is completed, the tin-germanium-sulfur-selenide film is taken out from the reaction solution, and gently rinsed with deionized water to remove incompletely reacted precursors on its surface.

After the chemical bath deposition step of the CdS buffer layer was completed, the In ₂ S ₃ buffer layer was also prepared by a similar procedure. Add 10 mL of 0.025 mol/L In(NO ₃ ) ₃ solution and 3 mL of glacial acetic acid (30%) into 13 mL of deionized water and stir for 5 minutes, then add 25 mL of 1 mol/L thioacetamide solution to the above solution. in solution. After the sample was immersed in the reaction solution, the water bath heating was started, the temperature was 70 °C, and the time was 14 minutes. After the reaction was complete, the samples were taken out and rinsed with deionized water.

The tin-germanium-sulfur-selenide film prepared by the above steps was put into a tube furnace and heated at 200° C. for 60 minutes under nitrogen protection. After cooling and taking out, the tin-germanium-sulfur-selenide film was immersed as a working electrode in a chloroplatinic acid solution with a concentration of 0.1 mmol/L, and irradiated with a 500W xenon lamp as a light source. Electrodeposition was started after the potential was set to -0.1 V _SCE . The deposition was stopped when the deposition power reached 5 mC/cm ² , thereby obtaining a tin-germanium-sulfur-selenide photoelectrode.

We have carried out various characterizations on the tin-germanium-sulfur-selenide photoelectrode obtained through the above steps, and Fig. 1 to Fig. 4 are the characterization results of the tin-germanium-sulfur-selenide thin film photoelectrode. Among them, Shanghai Chenhua CHI633C electrochemical workstation was used to test the photocurrent-potential curve of the tin-germanium-sulfur-selenide photoelectrode. A three-electrode system was used for the test, with tin-germanium-sulfur-selenide as the cathode, platinum as the anode, and SCE electrode as the reference electrode. AM 1.5G (100mW cm ^-2 ) solar simulator was used as the light source.

Fig. 1 shows the CZTS film prepared under Ge-free and low sulfur-selenium partial pressure (ie, the CZTS film prepared in Comparative Example 1) and the Ge-CZTS film prepared under the Ge content of 0.25 and high sulfur-selenium partial pressure (ie, the CZTS film prepared in Comparative Example 1) Surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 1). It can be seen from the SEM images of the surface and cross-section that the grains of the Ge-CZTS films prepared by increasing the Ge content and the partial pressure of sulfur and selenium increase significantly and the number of grain boundaries decreases.

Figure 2 shows the XRD patterns of the CZTS films prepared without Ge and under low sulfur and selenium partial pressure and the Ge-CZTS films prepared under Ge content of 0.25 and high sulfur and selenium partial pressure. It can be seen from Fig. 2 that the peak position of the characteristic diffraction peak of the prepared Ge-CZTS film is shifted to a larger angle than that of CZTS, and the half-width of the Ge-CZTS diffraction peak is narrower, indicating that the Ge-CZTS film higher crystallinity.

Figure 3 shows the visible (a) and ultraviolet (b) Raman spectra of CZTS films prepared without Ge and under low sulfur and selenium partial pressure and Ge-CZTS films with Ge content of 0.25 and high sulfur and selenium partial pressure. It can be seen from Fig. 3(a) that all the vibrational peaks are classified as characteristic peaks of CZTS and Ge-CZTS. It can be seen from Fig. 3(b) that there are ZnS impurity phases in the CZTS films prepared without Ge and under low sulfur and selenium partial pressure, while the Ge-CZTS films prepared with increasing Ge content and sulfur and selenium partial pressure do not contain ZnS impurity. Mutually.

Figure 4 shows the CZTS/CdS/In ₂ S ₃ /Pt photocathode prepared without Ge and under low sulfur and selenium partial pressure and the Ge-CZTS/CdS/In ₂ S prepared under high sulfur and selenium partial pressure with Ge content of 0.25 ₃ /Pt photocathode photocurrent-potential graph. It can be seen from Fig. 4 that the photocurrent of the Ge-CZTS photocathode prepared by simultaneously increasing the Ge content and the sulfur-selenium partial pressure is approximately tenfold improved at 0 V _RHE .

Fig. 5 shows the CZTS films prepared without Ge and under low sulfur and selenium partial pressure (ie, the CZTS film prepared in Comparative Example 1) and the Ge-CZTS films prepared under Ge content of 0.1 and high sulfur and selenium partial pressure (ie, the CZTS film prepared in Comparative Example 1) Surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 2). It can be seen from the SEM images of the surface and cross-section that the grains of the Ge-CZTS films prepared by increasing the Ge content and the partial pressure of sulfur and selenium increase significantly and the number of grain boundaries decreases.

Figure 6 shows the CZTS/CdS/In ₂ S ₃ /Pt photocathode prepared without Ge and under low sulfur and selenium partial pressure and the Ge-CZTS/CdS/In ₂ S prepared under high sulfur and selenium partial pressure with Ge content of 0.1 ₃ /Pt photocathode photocurrent-potential graph. It can be seen from Fig. 6 that the photocurrent of the Ge-CZTS photocathode prepared by simultaneously increasing the Ge content and the sulfur-selenium partial pressure is enhanced by about 7.6 times at 0 V _RHE .

Figure 7 shows the CZTS films prepared under Ge-free and low sulfur-selenium partial pressure (ie, the CZTS film prepared in Comparative Example 1) and the Ge-CZTS films prepared under the Ge content of 0.4 and high sulfur-selenium partial pressure (ie, the CZTS film prepared in Comparative Example 1) Surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 3). It can be seen from the SEM images of the surface and cross-section that the grains of the Ge-CZTS films prepared by increasing the Ge content and the partial pressure of sulfur and selenium increase significantly and the number of grain boundaries decreases.

Figure 8 shows the CZTS/CdS/In ₂ S ₃ /Pt photocathode prepared without Ge and under low sulfur and selenium partial pressure and the Ge-CZTS/CdS/In ₂ S prepared under high sulfur and selenium partial pressure with Ge content of 0.4 ₃ /Pt photocathode photocurrent-potential graph. It can be seen from Fig. 8 that the photocurrent of the Ge-CZTS photocathode prepared by simultaneously increasing the Ge content and the sulfur-selenium partial pressure is increased by about 4 times at 0 V _RHE .

Fig. 9 shows the CZTS films prepared without Ge and under low sulfur and selenium partial pressure (that is, the CZTS film prepared in Comparative Example 1) and the Ge-CZTS films prepared under the conditions of Ge content of 0.25 and low sulfur and selenium partial pressure (that is, the CZTS film prepared in Comparative Example 1) Surface and cross-sectional SEM images of the Ge-CZTS film prepared in Example 4). From the SEM images of the surface and cross-section, it can be seen that under the low partial pressure of sulfur and selenium, increasing the content of Ge will significantly reduce the grain size and increase the number of grain boundaries in the Ge-CZTS film.

Figure 10 shows the CZTS/CdS/In ₂ S ₃ /Pt photocathode prepared without Ge and under low sulfur and selenium partial pressure and the Ge-CZTS/CdS/In ₂ S ₃ prepared with Ge content of 0.25 and low sulfur and selenium partial pressure Photocurrent-potential plot of the /Pt photocathode. It can be seen from Fig. 10 that the photocurrent of the Ge-CZTS photocathode with a Ge content of 0.25 prepared at low sulfur and selenium partial pressure is doubled at 0 V _RHE . It can be seen that only increasing the content of germanium without increasing the partial pressure of sulfur and selenium can not improve the optoelectronic properties of the obtained film, but reduce its properties.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. a preparation method of tin-germanium-sulfur-selenide film, is characterized in that, the chemical formula of described tin-germanium-sulfur-selenide film is M1×1 M2 _×2 Sn _{1-x Ge x} S _1-y Se _y , wherein, M1 is a mixture of one or two of the metal elements Cu and Ag in an arbitrary proportion, M2 is a mixture of one or two of the metal elements Zn and Cd in an arbitrary proportion, 0<x ₁ ≤1, 0<x ₂ ≤1, 0.1≤x≤0.4, 0<y<1, a tin-germanium-sulfur-selenide film is prepared by a solution-spin coating-sulfurization method, including the following steps: Step 1, prepare a precursor solution: a mixture in any proportion of one or more of the nitrate, acetate, chloride, bromide or iodide salts containing M1 and M2 metal ions, a tin source, The germanium source and thioselenourea are respectively added to one or more mixed solvents in any ratio of ethylene glycol methyl ether, dimethyl sulfoxide, methanol, ethanol or ethylene glycol to be stirred and mixed to obtain a clear precursor body solution; Step 2, spin coating and calcination: aging the clarified precursor solution obtained in step 1; spin coating the aged precursor solution on the conductive substrate and calcining to obtain a precursor sample film; repeat the above spinning process. Coating and calcination process to obtain the desired thickness of the precursor sample film; Step 3, sulfur selenization: subjecting the precursor sample film obtained in step 2 to sulfur selenization treatment, and after the treatment is completed, the target tin germanium sulfur selenide film is obtained; During the preparation of the precursor solution, the germanium content, that is, the value of x, is controlled by adjusting the relative ratio of the tin source and the germanium source; In the sulfur selenization treatment, the partial pressure of sulfur and selenium is 0.2-5 atmospheres. 2. the preparation method of tin-germanium-sulfur-selenide film as claimed in claim 1, is characterized in that, in step 1, tin source is acetate, chloride salt, bromide containing Sn ²⁺ and Sn ⁴⁺ ion One or more arbitrary proportion mixtures in salt or iodide salt; Germanium source is one or more arbitrary proportion mixtures in germanium chloride, germanium bromide or germanium iodide; solvent is ethylene glycol One or a mixture of two or more of methyl ether, dimethyl sulfoxide, methanol, ethanol and ethylene glycol in any proportion. 3. the preparation method of tin-germanium-sulfur-selenide film as claimed in claim 1 or 2, is characterized in that, in step 3, the precursor sample film obtained in step 2 is placed in elemental sulfur vapor, elemental selenium vapor, sulfurization The sulfur selenization treatment is performed in one of hydrogen gas and hydrogen selenide gas or a combination thereof. 4. the preparation method of the tin-germanium-sulfur-selenide film as claimed in claim 1 or 2, is characterized in that, in step 3, the sulfide-selenide of the precursor sample film obtained in step 2 and germanium is carried out sulfur-selenide treatment , by adjusting the quality of germanium sulfide selenide to control germanium content. 5. The preparation method of tin-germanium-sulfur-selenide film as claimed in claim 4, wherein in step 3, the sulfur-selenide of germanium is: germanium sulfide, germanium sulfide, germanium selenide, germanium selenide one or a mixture of two or more in any ratio. 6. The method for the tin-germanium-sulfur-selenide film as claimed in claim 1 or 2, wherein in step 2, aging for 0-200 hours in an environment with a relative humidity of 5%-95%, at 200-550 calcined in air at ℃ for 1-60 minutes; in step 3, sulfide selenization is performed at a temperature of 450-600 ℃, and the sulfur selenization time is 20-120 minutes, and the tin germanium sulfide selenide film obtained after the sulfur selenization is completed Thickness is 0.05-5 microns.

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