Highly stable and efficient α-phase FA-based perovskite solar cells prepared in ambient air by strategically enhancing the interaction between ions in crystal lattices

Abstract

FAPbI₃ perovskite is an ideal candidate for efficient and stable perovskite solar cells (PSCs). Unfortunately, attaining photoactive α-phase FAPbI₃ under humid conditions is rather difficult due to the structural and moisture instability of α-phase FAPbI₃. To obtain high quality α-phase FAPbI₃ perovskite in ambient air, a strategy of incorporating methylamine thiocyanate (MASCN) as a stabilizer is introduced in this study. Due to its close effective ionic radius to I⁻, SCN⁻ is successfully incorporated into the lattice. The strong bond between SCN⁻ and Pb²⁺ and the strong hydrogen bonds between the N atom in SCN⁻ and FA⁺ lead to a high quality and stable α-phase FA-based perovskite at ambient 50 ± 5% RH even at room temperature. With this high quality film, air-processed PSCs with a maximum power conversion efficiency (PCE) of 19.06% can be realized in a p–i–n device. Moreover, it is also demonstrated that the stronger chemical bonding interaction between SCN⁻ and Pb²⁺ as well as the stronger hydrogen bonds between SCN⁻ and organic groups also improve the stability of PSCs. More than 90% of the initial efficiency is retained after 2000 hours of operation with maximum power point tracking under full sunlight illumination without an ultraviolet filter.