Facile and Low-Cost Sodium-Doping Method for High-Efficiency Cu2ZnSnSe4 Thin Film Solar Cells

摘要

We present a simple and low-cost sodium-doping method for Cu2ZnSnSe4 (CZTSe) thin film solar cells. In this method, a piece of soda-lime glass (SLG) is served as the sodium source and is placed on top of the CZTSe precursor thin film during selenization. It was observed that the grain growth and the hole-carrier concentration can be significantly improved by the diffusion of sodium from the top SLG. Through this approach, high-quality CZTSe absorber layer is obtained after the selenization, and the photoelectric conversion efficiencies (PCE) of 7.51% and 6.09% are achieved for CZTSe thin film solar cells deposited on a Mo-coated SLG substrate and a Mo-coated quartz substrate, respectively. The difference in PCE on SLG and quartz substrate revealed that Na diffusion from the bottom SLG substrate and the top SLG was most effective for the high-performance of CZTSe solar cell devices.