Using Soda-Lime Glass Transition Temperature to Enhance the Efficiency of Cu2ZnSn(S,Se)4 Solar Cell

Homogeneous large-grain structure of Cu2ZnSn(S,Se)4 (CZTSSe) absorber has been proven to be one of the conditions for high photoelectric conversion efficiency (PCE) devices. In this work, we explored that the different choices of selenization temperature had influences on the morphology, crystallinity, and electric properties of CZTSSe absorbers. With the selenization temperature of 540°C, the single-layer large-grain structure of CZTSSe absorber could be prepared, and grain boundary defects could be reduced. 540°C is also the transition temperature of the substrate (Soda-lime glass, SLG) of devices. The SLG softens at the transition temperature and the structure is unstable, resulting in Na entering CZTSSe better at 540°C than at a lower selenization temperature. The suitable Na diffusion can promote the growth of grains and help the corresponding device possesses the highest PCE (9.38%), which is also increased by ∼85% than ones prepared under the lower selenization temperature (PCE stayed at 5%). Therefore, the appropriate selenization conditions for the high-efficiency devices also need to consider the properties of the substrates. These conclusions also propose the new point on obtaining the optimal selenization condition for the high-performance CZTSSe devices.