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 (FAPbI₃) films through one-step spin-coating. The promoted formation of black trigonal phase α-FAPbI₃ with better crystallinity has been observed after the addition of NH₄SCN, together with the supression of the formation of yellow hexagonal phase δ-FAPbI₃. Planar perovskite solar cells (PVSCs) based on NH₄SCN-assisted formed α-FAPbI₃ 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 FAPbI₃. NH₄SCN simultaneously enhances the efficiency and moisture stability of FAPbI₃ based PVSCs through a single one-step solution method, facilitating their commercial fabrication and application.