Electron irradiation induced aging effects on radiative recombination properties of quadruple cation organic-inorganic perovskite layers

Abstract : Understanding the role of defects in hybrid organic inorganic perovskites (HOIPs) is critically important to engineer the stability and performance of photovoltaic devices based on HOIPs. Recent reports on multi-cation compositions of general formula (A$^1$,A$^2$,A$^3$,A$^4$)Pb(X$^1$,X$^2$,X$^3$)$_3$, where the A sites can be occupied by a distribution of 2–4 metallic/organic cations and X sites with halide anions have shown stabilization effects against the well-known methyl ammonium lead triiodide (CH$_3$NH$_3$PbI$_3$), although the underlying mechanism is not fully elucidated. Herein, polycrystalline layers of 4APb(IBr)$_3$ perovskite, where A is occupied by a combination of Cs$^+$ (cesium ion), GA$^+$ (guanidinium), MA$^+$ (methylammonium), and FA$^+$(formamidinium) ions were synthesized. To gain insight on the role of intrinsic defects, electron irradiation was used for introducing point defects in a controlled way in the quadruple-cation HOIPs. Our results show that the engineered defects in perovskites strongly influenced the absorption, photoluminescence, and time-resolved photoluminescence of these materials, probably due to introduction of additional energy levels that modify electronic and light emitting properties of the material. Furthermore, the irradiation-induced defects were found to strongly affect the aging behavior of HOIPs and modify their radiative recombination properties.