Efficient CH3NH3PbI3-x(SeCN)x perovskite solar cells with improved crystallization and defect passivation

The presence of grain boundaries and defects in perovskite films can be detrimental to performance of perovskite solar cells (PSCs), such as leading to nonradiative recombination and environmental instability. Additive engineering is a key tactic to control crystal growth and passivate defects of perovskite film. In this work, lead-free alkali metal additive of potassium selenocyanate (KSeCN) was firstly added in precursor solution to prepare a novel perovskite of CH 3 NH 3 PbI 3-x (SeCN) x . The SeCN − is substitute for I − to enhance structure stability, simultaneously facilitate nucleation, meanwhile, effectively increase crystalline grain size and passivate the defects. Finally, the power conversion efficiency of planar perovskite solar cells boosts from 14.34% to 18.41%, and the hysteresis reduces from 21% to 1.5%, nearly negligible. Our findings provide an avenue for crystalline regulation and defects passivation to further improve the performance of perovskite solar cells and propose a promising CH 3 NH 3 PbI 3-x (SeCN) x -based perovskite.