Effects of NH4SCN Additive in the FAPbI3 Perovskite Films in a Sequential Deposition Method

Abstract

This study determined the effect of introducing the NH4SCN additive in the precursor solution of PbI2 of a sequential deposition method in an open atmosphere to form FAPbI3 perovskite over a glass substrate. Adding NH4SCN leads to different intermediate layers according to the concentration of the additive. From an adequate concentration, an ionic substitution between I− and SCN− is promoted, providing a unique path for nucleation and growth of FAPbI3 due to significant changes in morphology. The intermediate layer with a proper amount of NH4SCN enhanced the physical properties of FAPbI3. It contributed to understanding the crystallinity and morphological conditions for favorable growth of FAPbI3 directly over a glass substrate. A concentration of 40% gave rise to the biggest grain size, homogeneous morphology, higher absorption, and prevalence of black phase in the α/δ phase coexistence. As a result, the perovskite with the NH4SCN additive showed a positive effect on the growth mechanisms and enhanced stability due to the mixed α/δ-phase and grain size ∼1350 nm. The preceding makes FAPbI3 film with a concentration of 40% a good option for application as stable perovskite in solar cells.