Xiang, WanchunWang, ZaiweiKubicki, Dominik J.Tress, WolfgangLuo, JingshanProchowicz, DanielAkin, SeckinEmsley, LyndonZhou, JiangtaoDietler, GiovanniGraetzel, MichaelHagfeldt, Anders2019-06-182019-06-182019-06-182019-01-1610.1016/j.joule.2018.10.008https://infoscience.epfl.ch/handle/20.500.14299/157492WOS:000457552800018All-inorganic perovskite films hold promise for improving the stability of perovskite solar cells (PSCs). However, the 3D alpha phase of narrow-bandgap inorganic perovskites is thermodynamically unstable at room temperature, limiting the development of high-performance inorganic PSCs. Here, we show that europium doping of CsPbI2Br stabilizes the alpha phase of this inorganic perovskite at room temperature. We rationalize it by using solid-state nuclear magnetic resonance and high-angle annular dark-field scanning transmission electron microscopy, which show that europium is incorporated into the perovskite lattice. We demonstrate amaximum power-conversion efficiency of 13.71% for an inorganic PSC with the CsPb0.95Eu0.05I2Br perovskite and alpha stable power output of 13.34%. Using electroluminescence we show that incorporation of europium reduces non-radiative recombination, resulting in high open-circuit voltage of 1.27 V. The devices retain 93% of the initial efficiency after 370 hr under 100 mW cm(-2) continuous white light illumination under maximum-power point-tracking measurement.Energy & Fuelshalide perovskiteshybrid perovskitesphase segregationstabilitystabilizationalpha-cspbi3degradationcationsnmrtext::journal::journal article::research article