阅读说明：本技术 一种简便的用于改善铜锌锡硫硒薄膜光伏器件背接触的方法 (Simple and convenient method for improving back contact of copper-zinc-tin-sulfur-selenium film photovoltaic device ) 是由 王玲玲 王少彤 王雁芹 张昕彤 刘益春 于 2020-06-02 设计创作，主要内容包括：本发明提供一种简便的用于改善铜锌锡硫硒薄膜光伏器件背接触的方法,属于光电器件制备技术领域。对镀Mo的钠钙玻璃表面进行紫外-臭氧处理；在处理后的Mo玻璃表面通过溶液旋涂法制备铜锌锡硫或铜锌锡硒预制膜；对CZTS预制膜进行高温硒化或高温硫化处理得到CZTSSe薄膜。本发明中对镀Mo的钠钙玻璃表面进行适当的紫外-臭氧处理,可在Mo玻璃表面原位形成超薄、致密、均匀的Mo的氧化层,可有效阻止Se与Mo及CZTSSe与Mo的直接接触,避免Mo玻璃过度硒化、及CZTSSe的相分解,从而降低器件串联电阻、减少界面电荷复合；有利于载流子传输；得到在Mo玻璃表面具有更强附着性的CZTS预制膜,有效减少CZTSSe/Mo玻璃界面的孔洞、起皮等现象。(The invention provides a simple and convenient method for improving back contact of a copper-zinc-tin-sulfur-selenium film photovoltaic device, and belongs to the technical field of photoelectric device preparation. Carrying out ultraviolet-ozone treatment on the surface of the Mo-plated soda-lime glass; preparing a copper-zinc-tin-sulfur or copper-zinc-tin-selenium prefabricated film on the surface of the treated Mo glass by a solution spin coating method; and carrying out high-temperature selenization or high-temperature vulcanization treatment on the CZTS prefabricated film to obtain the CZTSSe film. According to the invention, the surface of the Mo-plated soda-lime glass is subjected to proper ultraviolet-ozone treatment, an ultrathin, compact and uniform Mo oxide layer can be formed in situ on the surface of the Mo glass, the direct contact between Se and Mo and between CZTSSe and Mo can be effectively prevented, and the excessive selenization of the Mo glass and the phase decomposition of CZTSSe are avoided, so that the series resistance of a device is reduced, and the interface charge recombination is reduced; is beneficial to the transmission of current carriers; the CZTS prefabricated film with stronger adhesiveness on the surface of the Mo glass is obtained, and the phenomena of holes, peeling and the like of a CZTSSe/Mo glass interface are effectively reduced.)

1. A simple method for improving the back contact of a copper zinc tin sulfur selenium thin film photovoltaic device is characterized by comprising the following steps:

1) carrying out ultraviolet-ozone treatment on the surface of the Mo substrate;

2) preparing a CZTS or CZTSe prefabricated film on the surface of the Mo glass subjected to ultraviolet-ozone treatment by using a traditional solution spin-coating method;

3) and carrying out high-temperature selenization or high-temperature vulcanization treatment on the CZTS or CZTSe prefabricated film to obtain the CZTSSe film.

2. The method of claim 1, wherein the method comprises the steps of: the CZTSSe thin film is a CZTSSe thin film with various S/Se ratios, and comprises a CZTS thin film and a CZTSe thin film.

3. The method of claim 1, wherein the method comprises the steps of: the ultraviolet-ozone treatment process comprises ultraviolet illumination, ozone atmosphere treatment and ultraviolet-ozone combined treatment.

4. The method of claim 1 or 3, wherein the method comprises the following steps: in the ultraviolet-ozone treatment process, the ultraviolet irradiation light intensity is 0-50 mW/cm²。

5. The method of claim 1 or 3, wherein the method comprises the following steps: the concentration of ozone in the ultraviolet-ozone treatment process is 0-1 ppm.

6. The method of claim 1 or 3, wherein the method comprises the following steps: the treatment time in the ultraviolet-ozone treatment process is 1-40 min.

7. The method of claim 1 or 3, wherein the method comprises the following steps: the distance between the Mo substrate and the ultraviolet light source is 2-35 cm in the ultraviolet-ozone treatment process.

8. The method of claim 1, wherein the method comprises the steps of: the method for preparing the CZTS or CZTSe prefabricated film by using the traditional solution spin-coating method in the step 2) comprises the following specific steps: and spin-coating the prepared CZTS or CZTSe precursor solution on a Mo substrate, then placing the Mo substrate on a hot plate for annealing, and repeating the spin-coating and annealing operations for a plurality of times to obtain a CZTS or CZTSe prefabricated film with the target thickness of 1-3 mu m.

9. The method of claim 8, wherein the method comprises the steps of: the specific preparation method of the CZTS or CZTSe precursor solution comprises the following steps: taking a copper compound, a zinc compound, a tin compound, a sulfur or selenium compound or four simple substances of copper, zinc, selenium, sulfur or selenium as solutes, taking one or more of DMF, DMSO, ethylene glycol monomethyl ether, ethanedithiol, ethanolamine, thioglycolic acid and other solvents as solvents, mixing the solutes and the solvents, magnetically stirring uniformly, centrifuging, taking supernate, and finally preparing the CZTS or CZTSe precursor solution.

10. The method of claim 1, wherein the method comprises the steps of: the specific method of the step 3) is as follows: placing the CZTS prefabricated film and a selenium source into a graphite box, and placing the graphite box into a rapid annealing furnace for high-temperature selenization treatment to obtain a CZTSSe film; putting the CZTS prefabricated film and a sulfur source into a graphite box, and putting the graphite box into a rapid annealing furnace for high-temperature vulcanization treatment to obtain a CZTS film; and placing the CZTSe prefabricated film and a selenium source into a graphite box, and placing the graphite box into a rapid annealing furnace for high-temperature selenization treatment to obtain the CZTSe film.

Technical Field

The invention belongs to the technical field of photoelectric device preparation, and particularly relates to a method for improving the performance of a CZTSSe/Mo glass back contact interface in a copper zinc tin selenium (CZTSSe) thin film photovoltaic device.

Background

The CZTSSe material with the kesterite structure has a very high absorptivity (due to a proper energy band structure, an adjustable band gap width (1-1.5 eV) and a very high band gap width (1-1.5 eV)>10⁴cm^-1) And the advantages of rich earth reserves of the constituent elements, safety, no toxicity, low cost and the like make the compound have good application prospect in the photoelectric field, in particular in the technical fields of photoelectrochemistry and solar cells. CZTSSe solar cells have a similar composition structure to Copper Indium Gallium Selenide (CIGS) cells, typically using molybdenum (Mo) metal as the back contact electrode. However, in practical research and application, there are many problems in the contact between the CZTSSe absorption layer and the Mo back electrode, which directly affects the performance of the CZTSSe battery device to be further improved. Firstly, in the high-temperature selenization (or sulfurization) treatment process, Se (or S) and substrate Mo can generate chemical reaction to generate MoSe₂(or MoS)₂) Layer of MoSe of suitable thickness₂(or MoS)₂) The layer will form a favorable ohmic contact with the CZTSSe absorbing layer, which is beneficial to the performance of the cell, but the MoSe is too thick₂(or MoS)₂) The layer can increase the series resistance of the device, block the transmission of current carriers and influence the performance of the device; secondly, chemical reaction also occurs between the CZTSSe absorption layer and the Mo substrate at high temperature, so that the decomposition of CZTSSe and the generation of unfavorable secondary phases are promoted, and the influence on the performance of the battery device is undoubtedly unfavorable; meanwhile, in the process of preparing the CZTSSe thin film by a common solution method, the wettability of a CZTS (or CZTSe) precursor solution on the surface of Mo glass and the adhesiveness of a CZTS (or CZTSe) prefabricated film on the surface of Mo glass are not strong, so that the problem of interfacial holes caused by shrinkage of the thin film during the selenization (or sulfurization) treatment in the later stage can be aggravated, the CZTSSe/Mo interfacial contact is directly influenced, and even the thin film is caused to fall off.

Because the back contact quality of the CZTSSe film has direct relevance with the performance of a photovoltaic device, the improvement of the back contact of the CZTSSe film becomes a key point and a difficulty in the research field of CZTSSe film photovoltaic materials. To improve the back contact of CZTSSe thin films, many scientists are at the interface of CZTSSe and Mo substrate back contactSurface-introduced ZnO, Ag, C, Bi, Ti, TiN, and Al₂O₃The ultrathin interface layers are used for blocking direct contact of CZTSSe and Mo so as to avoid or reduce the occurrence of chemical reactions between Mo and Se (or S) and between Mo and CZTSSe at the interface, but the interface modification layers are generally prepared by large-scale instruments such as ALD (atomic layer deposition), magnetron sputtering and the like, the instruments are expensive and complex in process, and new phases or defects are inevitably introduced into the CZTSSe/Mo back contact interface due to the introduction of non-component element substances, so that the performance of a photovoltaic device is influenced. At present, part of the subject groups abandon the method of modifying an out-phase interface layer, and a high-temperature annealing process is adopted to oxidize the surface of Mo glass and grow MoO in situ₂、MoO₃And the interface layer achieves a good improvement effect. Researches find that in addition to the general blocking effect of the interface layer, the addition of molybdenum oxide can promote the diffusion of Na so as to promote the growth of CZTSSe grains, reduce grain boundaries and further be beneficial to improving the performance of a photovoltaic device. However, the MoO grown by high-temperature in-situ annealing₂、MoO₃The layer is usually thick, not dense enough and rough surface, the film thickness, film forming compactness and uniformity are difficult to control, and the excessive MoO₂、MoO₃The layer will increase the interface resistance, affecting the transport of charge at the back contact interface; meanwhile, the molybdenum oxide layer with uniformity and poor compactness inevitably increases the possibility of direct contact between CZTSSe and Mo, so that the generation of decomposition reaction of the CZTSSe layer and the generation of unfavorable secondary phases at an interface are caused; in addition, the high temperature treatment process increases the process complexity and limits the practical application of the process.

Disclosure of Invention

The invention provides a simple method for improving the back contact of a copper-zinc-tin-sulfur-selenium thin film photovoltaic device, which is used for simply carrying out ultraviolet-ozone treatment on Mo-plated soda-lime glass to improve the back contact of a CZTSSe/Mo thin film.

The technical scheme of the invention is that the method comprises the following steps:

1) carrying out ultraviolet-ozone treatment on the surface of the Mo substrate;

2) preparing a CZTS or CZTSe prefabricated film on the surface of the Mo glass subjected to ultraviolet-ozone treatment by using a traditional solution spin-coating method;

3) and carrying out high-temperature selenization or high-temperature vulcanization treatment on the CZTS or CZTSe prefabricated film to obtain the CZTSSe film.

The CZTSSe thin film is a CZTSSe thin film with various S/Se ratios, and comprises a CZTS thin film and a CZTSe thin film.

The ultraviolet-ozone treatment process comprises ultraviolet illumination, ozone atmosphere treatment and ultraviolet-ozone combined treatment.

The ultraviolet irradiation light intensity in the ultraviolet-ozone treatment process is 0-50 mW/cm²。

The concentration of ozone in the ultraviolet-ozone treatment process is 0-1 ppm.

The treatment time in the ultraviolet-ozone treatment process is 1-40 min.

The distance between the Mo substrate and the ultraviolet light source in the ultraviolet-ozone treatment process is 2-35 cm.

The invention relates to a method for preparing a CZTS or CZTSe prefabricated film by using a traditional solution spin-coating method, which comprises the following specific steps: and spin-coating the prepared CZTS or CZTSe precursor solution on a Mo substrate, then placing the Mo substrate on a hot plate for annealing, and repeating the spin-coating and annealing operations for a plurality of times to obtain a CZTS (or CZTSe) prefabricated film with the target thickness of 1-3 mu m.

The specific preparation method of the CZTS or CZTSe precursor solution provided by the invention comprises the following steps: taking four compounds of a copper compound, a zinc compound, a tin compound and a sulfur (or selenium) compound or four simple substances of copper, zinc, selenium and sulfur (or selenium) as solutes, taking one or more medicines in solvents such as DMF, DMSO, ethylene glycol monomethyl ether, ethanedithiol, ethanolamine, thioglycolic acid and the like as solvents, mixing the solutes and the solvents, magnetically stirring uniformly, centrifuging, taking supernate, and finally preparing a CZTS (or CZTSe) precursor solution.

The specific method of the step 3) comprises the following steps: placing the CZTS prefabricated film and a selenium source into a graphite box, and placing the graphite box into a rapid annealing furnace for high-temperature selenization treatment to obtain a CZTSSe film; putting the CZTS prefabricated film and a sulfur source into a graphite box, and putting the graphite box into a rapid annealing furnace for high-temperature vulcanization treatment to obtain a CZTS film; and placing the CZTSe prefabricated film and a selenium source into a graphite box, and placing the graphite box into a rapid annealing furnace for high-temperature selenization treatment to obtain the CZTSe film.

The preparation method of the ultrathin, homogeneous and compact Mo oxide interface layer, which is simple and can be realized at low temperature, is obtained, so that the quality of the CZTSSe/Mo interface is improved, the problem of CZTSSe/Mo back contact in a photovoltaic device is solved, and the preparation method is very important and has profound significance to the field of CZTSSe thin film photovoltaic devices.

The method realizes the oxidation of the Mo substrate at low temperature, and forms a uniform, compact and thin Mo oxide layer on the Mo surface to prevent the occurrence of Mo over-selenization (or sulfuration) and chemical decomposition reaction between Mo and CZTSSe absorption layers, and promotes the growth of CZTSSe crystal grains; in addition, the method also realizes effective cleaning of the Mo surface, improves the wettability of the CZTS (or CZTSe) precursor liquid on the Mo surface in the preparation process of the solution method, promotes the flatness of the prefabricated film on the Mo surface to be improved, enhances the adhesion of the film on the surface of the substrate, further effectively prevents the film from falling off, solves the problems of holes and the like existing on a CZTSSe/Mo interface, and optimizes the CZTSSe/Mo back contact performance. The simple and controllable in-situ film treatment process can be applied to the fields of CIGS, CIS and other various film photovoltaic devices, and has good practical value.

The invention has the beneficial effects that:

1. the Mo-plated soda-lime glass is subjected to ultraviolet-ozone treatment, so that an oxide barrier layer of Mo can be grown in situ on the surface of the Mo glass, and the common Ag, TiN and Al in the prior art are avoided₂O₃And defects, recombination and other problems caused by the introduction of non-constituent elements in the interface barrier layer are solved, and the performance of the device is improved.

2. The Mo-plated soda-lime glass is subjected to ultraviolet-ozone treatment, and a more ultrathin and compact Mo oxide layer can be grown in situ on the surface of the Mo glass. Compared with an oxide layer of Mo formed by in-situ annealing, the method has the advantages that: (1) the thickness of the molybdenum oxide layer prepared by the method is ultrathin, controllable and compact, the molybdenum oxide layer has less negative influence on the series resistance of the device, and the molybdenum oxide layer can more effectively and comprehensively block the diffusion of Se (or S)And their over-reaction with Mo to form too thick MoSe₂(MoS₂) Layer, thus reduce the device series resistance, improve its performance; (2) the compact oxide layer can effectively prevent Mo from directly contacting with CZTSSe, avoid the occurrence of chemical reaction between Mo and CZTSSe, reduce the generation of unfavorable secondary phase caused by the decomposition of CZTSSe, and further improve the performance of the device.

3. The ultraviolet-ozone treatment can enable the surface of the Mo-plated soda-lime glass to form a molybdenum oxide layer with higher oxygen content, is more beneficial to the diffusion of sodium ions in the soda-lime glass to the surface of the Mo glass, and promotes the growth of CZTSSe crystal grains.

4. Compared with the process of introducing other interface layers, the ultraviolet-ozone treatment process is simpler, takes shorter time, does not need a high-temperature environment and can be realized at a low temperature.

5. The Mo-plated soda-lime glass can be further cleaned on the basis of ultrasonic cleaning by ultraviolet-ozone treatment, pollutants can be effectively removed by photosensitive oxidation with organic pollutants, the surface flatness of the Mo substrate is improved, and therefore the wettability and the bonding strength of the surface of the Mo glass are improved, CZTS (or CZTSe) precursor liquid is more easily attached to the surface of the Mo substrate, and holes are more tightly, uniformly and effectively removed by CZTSSe/Mo interface combination.

6. The ultraviolet-ozone treatment process can form a compact oxide interface layer and clean the surface of a substrate, and has practical application significance for a plurality of photovoltaic devices needing interface improvement.

Drawings

FIG. 1 is a schematic view of an ultraviolet-ozone treated Mo substrate;

FIG. 2 is a SEM surface and cross-sectional comparison of an untreated Mo substrate and a Mo substrate treated by UV-ozone treatment and a Mo substrate sample treated by in-situ air annealing, wherein (a), (c) and (e) are respectively surface scanning electron micrographs of the untreated Mo substrate, the Mo substrate treated by UV-ozone treatment and the Mo substrate sample treated by in-situ air annealing, and the length of a scale in the SEM surface and the cross-sectional comparison show that the Mo substrate sample treated by UV-ozone treatment and the Mo substrate sample treated by in-situ air annealing are 1 μm; in the figure, (b), (d) and (f) are respectively cross-sectional scanning electron microscope images of an untreated Mo substrate, an ultraviolet-ozone treated Mo substrate and an in-situ air annealing treated Mo substrate sample, wherein the length of a scale in the images represents 500 nm;

FIG. 3 is a comparison of XPS plots of the surface of an untreated Mo substrate and a Mo substrate sample treated with UV-ozone at different times, wherein (a) is a XPS plot of the surface of an untreated Mo substrate, (b) is a XPS plot of the surface of a Mo substrate sample treated with UV-ozone for 5min, and (c) is a XPS plot of the surface of a Mo substrate sample treated with UV-ozone for 10min, and wherein O is a XPS plot of the surface of a Mo substrate sample treated with UV-ozone for 10min₂Mo represents Mo having adsorbed oxygen;

FIG. 4 is a comparison graph of contact angle tests performed on an untreated Mo substrate and a UV-ozone treated Mo substrate surface with a CZTS precursor solution;

FIG. 5 is an image comparison under an optical microscope of a sample obtained by spin-coating a layer of CZTS precursor solution on the surface of an untreated Mo substrate and an UV-ozone treated Mo substrate and annealing, wherein (a) and (b) are test charts of a single-layer CZTS pre-formed film sample prepared on the untreated Mo substrate and the UV-ozone treated Mo substrate, respectively, and the length of a scale in the chart represents 200 μm;

FIG. 6 is an image comparison under an optical microscope of a sample prepared by spin-coating a layer of CZTS precursor solution on the surface of an untreated Mo substrate and an UV-ozone treated Mo substrate, annealing and then selenizing, wherein (a) and (b) are test charts of a single-layer CZTSSe thin film sample prepared on the untreated Mo substrate and the UV-ozone treated Mo substrate respectively, and the length of a scale in the chart represents 200 μm;

fig. 7 is a SEM cross-sectional comparison view of samples after the CZTSSe thin film is prepared on the surface of an untreated Mo substrate and an ultraviolet-ozone treated Mo substrate, in which (a) is a SEM cross-sectional view of a CZTSSe thin film sample prepared on an untreated Mo substrate, and (b) is a SEM cross-sectional test view of a CZTSSe thin film sample prepared on an ultraviolet-ozone treated Mo substrate, in which the length of a scale bar represents 1 μm.

Detailed Description