Large-Grain Double Cation Perovskites With 18 Mu S Lifetime And High Luminescence Yield For Efficient Inverted Perovskite Solar Cells

Recent advancements in perovskite solar cell performance were achieved by stabilizing the alpha-phase of FAPbI(3) in nip-type architectures. However, these advancements could not be directly translated to pin-type devices. Here, we fabricated a high-quality double cation perovskite (MA(0.07)FA(0.93)PbI(3)) with low bandgap energy (1.54 eV) using a two-step approach on a standard polymer (PTAA). The perovskite films exhibit large grains (similar to 1 mu m), high external photoluminescence quantum yields of 20%, and outstanding Shockley-Read-Hall carrier lifetimes of 18.2 mu s without further passivation. The exceptional optoelectronic quality of the neat material was translated into efficient pin-type cells (up to 22.5%) with improved stability under illumination. The low-gap cells stand out by their high fill factor (similar to 83%) due to reduced charge transport losses and short-circuit currents >24 mA cm(-2). Using intensity-dependent quasi-Fermi level splitting measurements, we quantify an implied efficiency of 28.4% in the neat material, which can be realized by minimizing interfacial recombination and optical losses.