Nonmonotonic Photostability of BA<sub>2</sub>MA<sub><i>n</i>–1</sub>Pb<sub><i>n</i></sub>I<sub>3<i>n</i>+1</sub> Homologous Layered Perovskites
Natalia N. Udalova, Sergey A. Fateev, Elizaveta M. Nemygina, Andrea Zanetta, Giulia Grancini, Eugene A. Goodilin, Alexey B. Tarasov
Abstract
Layered lead halide perovskites (2D LHPs) are attracting considerable attention as a promising material for a new generation of solar cell devices. LHPs have been presented as a more stable alternative to the more widespread 3D bulk perovskite materials; however, a critical analysis of their photostability is still lacking. In this work, we perform a comparative study between BA 2 MA n –1 Pb n I 3 n +1 (BA─butylammonium and MA─methylammonium) 2D LHPs with different dimensionalities ( n = 1–3) and MAPbI 3 3D perovskites. We compare different stability testing protocols including photometrical determination of iodine-containing products in nonpolar solvents, X-ray diffraction, and photoluminescence (PL) spectroscopy. The resulting trends of the photostability in an inert atmosphere based on PL spectroscopy measurements demonstrate a nonmonotonic dependence of the degradation rate on the perovskite layer thickness n with a “stability island” at n ≥ 3, which is caused by a combination of antibate factors of electronic structures and chemical compositions in the family of 2D perovskites. We also identify a critical oxygen concentration in the surrounding environment that affects the mechanism and strongly enhances the rate of layered perovskite photodegradation.