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

Abstract

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