Secondary phases in Cu2ZnSnS4 thin film solar cell: The role of interfaces

Cu2ZnSnS4 (CZTS) is a complex quaternary compound semiconductor, it is easy to form secondary phases during preparation, like Cu2S and ZnS, and there are interfaces between these secondary phases and the matrix. The interfaces are also key factors in determining the photovoltaic performance of CZTS. So, we used the first-principles calculation method to research the interfaces between the secondary phase Cu2S, ZnS and CZTS thin films. The influence of the secondary phase is clarified by analyzing the interface electronic properties of secondary phase and CZTS. The existence of Cu2S secondary phase is harmless to the photovoltaic performance of CZTS, and can even promote the improvement of photovoltaic performance. Therefore, it is not necessary to avoid it when preparing CZTS films, and even it can be used. However, the existence of ZnS secondary phase is harmful to the photovoltaic performance of CZTS, which should be avoided when preparing CZTS films.