Quadruple cation mixed halide perovskite, GA0.015Cs0.046MA0.152FA0.787Pb­(I0.815Br0.185)3, single crystals were grown for the first time using an inverse temperature crystallization process. Solar cell devices in n-i-p stack configuration using thin films of the same materials showed power conversion efficiency above 20%. Complementary time-resolved spectroscopy confirmed that polycrystalline thin films and single crystals identically composed exhibit similar carrier dynamics in the picosecond range. Cooling of excited carriers and bandgap renormalization occur on the same time scale of 200–300 fs. The radiative recombination coefficient (1.2 × 10–9 cm3/s) is comparable to values reported for a GaAs semiconductor. At low excitation density, a long carrier lifetime of 3.2 μs was recorded possibly due to the passivation of recombination centers. This study clarifies discrepancies about the lifetime of hot carriers, the impact of radiative recombination, and the role of recombination centers on solar cell performance. The quadruple cation perovskites displayed short time dynamics with slow recombination of charge carriers.

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.