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

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 (A¹,A²,A³,A⁴)Pb(X¹,X²,X³)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 (CH₃NH₃PbI₃), 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.