Improving the photovoltaic performance of planar heterojunction perovskite solar cells by mixed solvent vapor treatment.

The grain size of perovskite films is a key factor to optimize the performance of perovskite photovoltaic devices. Herein, a new route is developed in this paper to prepare CHNHPbI (MAPbI) films with a better morphology and crystallization. This method includes the spin coating deposition of perovskite films with a precursor solution of PbI and CHNHI at the molar ratio 1 : 1 and thermal annealing (TA). The thermal annealing is conducted with a thermal-induced process to realize grain growth with solvent evaporation. In addition, a mixed solvent vapor treatment in acetic acid with chlorobenzene (HAc/CB) improves the morphology and crystallization of films further. As a result, the photovoltaic device based on the perovskite film treated by mixed HAc/CB solvent exhibits the best efficiency of 13.15% in comparison to the control device with 11.44% under AM 1.5G irradiation (100 mW cm).