American Association for the Advancement of Science, Science, 6548(372), p. 1327-1332, 2021
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Suppressing nucleation over large areas Although formamidinium-based lead iodide (PbI 2 ) perovskites have a favorable bandgap and good thermal stability, the difficulty in controlling nucleation makes it difficult to grow high-quality, large-area films compared with methylammonium counterparts. Bu et al. show that adding N -methyl-2-pyrrolidone to the perovskite precursors forms an adduct with PbI 2 that promotes the formation of the desired black α-phase at room temperature. The addition of potassium hexafluorophosphate eliminated hysteresis by passivating interfacial defects and promoted long-term thermal stability at 85°C in unencapsulated devices. Large-area modules (17 square centimeters) achieved power conversion efficiencies of 20.4%. Science , abh1035, this issue p. 1327