Study On Preparation Of Cu₂ZnSn（S,Se）₄ Thin Films By Selenization

Cu₂Zn Sn（S,Se）₄（CZTSSe）is considered as a promising absorbing layer material in solar cell because of its abundant reserves in nature,large light absorption coefficient and adjustable band gap.At present,the cadmium telluride and copper indium gallium selenide solar cells that have been put into commercial production show excellent photoelectric characteristics,and the photoelectric conversion efficiency is over 22%.CZTSSe has a kesterite structure,which is very similar to the structure of the above two absorber layers in batteries.It can be regarded as their direct derivative and it is considered a material with great potential.Up to now,the reported efficiency of CZTSSe solar cell is up to 12.62%,which is prepared by magnetron sputtering method.But this efficiency is still far below the theoretically calculated result of more than 30%.The severe volume expansion resulted by the sulfurization and selenization of the metal film causes the internal stress in the film to change greatly,microcracks and holes appear,which limits the further improvement of the quality of the large-area film.In order to solve the problem of volume change during the thin film annealing process,the CZTS precursor was prepared by magnetron sputtering and then annealed statically in a tube furnace.The feasibility of precursor selenization and the influence of different preparation conditions on CZTSSe thin films were studied.The CZTSSe films prepared under the optimal conditions were applied to photovoltaic devices.The following results were obtained:（1）The selenization of Cu₂S,Zn S and Sn S₂single-component thin films proved it is feasible to selenize sulfides by using tube furnace with using tube furnace with multi temperature region.The CZTSSe thin film precursor was prepared by co-sputtering Cu₂S,Zn S and Sn S₂targets.The film element was analyzed and the CZTSSe film was preliminarily prepared by selenization annealing.（2）The preparation conditions were explored in order to improve the quality of CZTSSe thin film.The annealing temperature for selenization,sulfur atmosphere supplementation during sputtering and annealing time are included.The results show that sulfur supplementation during the sputtering process can effectively prevent the film from being damaged during the selenization process caused by the loss of sulfur.The best condition for preparing CZTSSe film is selenization at 500℃for 30min.（3）The CZTSSe thin film is used as the absorption layer to make preliminary explorations on the preparation of CZTSSe solar cells.The prepared cell structure was SLG/Mo/CZTSSe/Cd S/i-Zn O/ITO/Al,and the results showed a certain photoelectric conversion efficiency,indicating that the prepared CZTSSe has certain photovoltaic characteristics.