Thiocyanate assisted performance enhancement of formamidinium based planar perovskite solar cells through a single one-step solution process

Thiocyanate ammonium (NH4SCN) is introduced into the fabrication of formamidinium lead triiodide (FAPbI(3)) films through one-step spin-coating. The promoted formation of black trigonal phase alpha-FAPbI(3) with better crystallinity has been observed after the addition of NH4SCN, together with the supression of the formation of yellow hexagonal phase delta-FAPbI(3). Planar perovskite solar cells (PVSCs) based on NH4SCN-assisted formed alpha-FAPbI(3) films with high quality present a highest power conversion efficiency of 11.44% when 30 mol% NH4SCN is applied. Notably, the addition of NH4SCN is found to enhance the moisture stability of the perovskite. As a result, the planar PVSCs with 30 mol% NH4SCN additive show improved stability under ambient conditions (RH: 30-40%) over those based on pristine FAPbI(3). NH4SCN simultaneously enhances the efficiency and moisture stability of FAPbI(3) based PVSCs through a single one-step solution method, facilitating their commercial fabrication and application.