Additive Engineered Quasi Two-dimensional Dion-Jacobson Phase Perovskite with p-Xylylene diamine Organic Spacer for Highly Efficient and Stable Solar Cells*

Two-dimensional (2D) Dion-Jacobson (DJ) organic-inorganic halide perovskites have recently emerged as promising photovoltaic materials due to their unique photophysical properties, as rich structural diversity and superb ambient stability. Here, we demonstrate additive engineering of p-Xylylene diamine organic spacer-based n-4 phase  2D D-J perovskite for efficient and stable solar cells applications. We observe significant improvement of film morphology, phase purity, crystallinity and carrier mobility after ammonium thiocyanate (NH₄SCN) additive treatment as evidenced by UV-visible spectroscopy, XRD and SEM. Transient and impedance spectroscopy confirm the suppression of defects in additive treated perovskite films. The PCE of the NH₄SCN treated perovskite device increased significantly from 12.9% to 17% wrt untreated device. The unencapsulated NH₄SCN treated perovskite devices maintains 75% of its initial PCE after 1000 h of continuous storage with a humidity level of 50 ± 5%.