Highly efficient solar cells based on Cl incorporated tri-cation perovskite materials

Abstract

Though mixed cation hybrid organic–inorganic perovskite materials are of promise due to the high efficiency and long-term stability of the corresponding devices, a fundamental understanding on the function of the mixed cation system is still unclear. Herein, we systematically investigate the roles of the Cs cation and Cl anion in inverted structure perovskite solar cells based on Cs_xFA_0.2MA_0.8−xPb(I_1−yCl_y)₃. For the role of Cs, we observe that an appropriate amount of Cs in the film could improve the crystal quality of the film and optimize the energy band alignment of the device, thus reducing non-radiative recombination and promoting the charge transport efficiently. The presence of Cl with a suitable concentration also possesses these functions. More importantly, the two limitations for the application of the devices, hysteresis and performance instability, could also be addressed to some extent. Thus a high power conversion efficiency of 20.31% has been realized and a universal method for constructing highly-efficient perovskite solar cells has been provided.