Improving the efficiency of Cu2ZnSn(S, Se)4 solar cells by post-heating treatment precursor films

In the solution method, the surface morphology characteristic of the precursor film is essential for obtaining the high quality of the absorber layer. Herein, the post-heating treatment (PHT) precursor films were adopted to modify the morphology significantly and the effects of different PHT temperatures on the properties of precursor films, absorber layer films, and photovoltaic devices were investigated. The precursor film with a more porous surface could be obtained by PHT, which facilitates the downward diffusion of Se easily during sulfoselenization and the formation of a large-grain-spanning monolayer structure. Furthermore, the Cu 2 ZnSn(S, Se) 4 absorber layer surface holes were significantly reduced, owing to sufficient grain growth during sulfoselenization. As a result, the device efficiency with PHT was increased to 11.07% mainly due to improved Cu 2 ZnSn(S, Se) 4 absorber spectral response. This study might provide a new potential method for adjusting precursor film morphology and thus enhancing the corresponding device performance.