Extremely Long Electron Lifetime in Spontaneously Passivated Polycrystalline Perovskite Layers via Illumination‐Assisted Trap Filling

ABSTRACT Perovskite solar cells (PSCs) are promising next‐generation photovoltaics. The high performance of PSCs is attributed to the long carrier lifetimes of perovskite photoabsorbers. However, the carrier lifetimes of polycrystalline perovskite layers, which serve as the photoabsorbers in practical PSCs, have remained limited to several tens of microseconds. Thus, to demonstrate the performance of perovskite photoabsorbers, achieving long carrier lifetimes in polycrystalline perovskite layers is imperative. In this study, a sub‐millisecond electron‐lifetime of a polycrystalline perovskite layer was demonstrated. This prolonged carrier lifetime was enabled by a combination of a spontaneous perovskite passivation technique, which circumvents exposure of the modulated interface to the atmosphere, and time‐resolved microwave conductivity (TRMC) with trap filling via photoexcitation. Under optimal trap filling, with negligible intensity relative to that for the 1 sun condition, a long electron lifetime of up to 547 ± 9 µs was achieved under illumination‐assisted trap filling for a perovskite layer in the presence of a heterointerface. This is the first observation of carrier lifetime extension in polycrystalline perovskite photoabsorbers via photoexcitation trap filling in TRMC measurements. This study elucidates the effectiveness of emerging spontaneous heterointerface modulation techniques, strengthens characterization techniques for PSC components, and provides guidance for the development of PSCs.