White light-induced halide segregation in triple-cation mixed halide perovskites studied by in-situ fast scanning nano-XRF at the NANOSCOPIUM beamline, Synchrotron SOLEIL

Abstract In-situ study of the variation of the chemical composition of triple-cation mixed halide perovskites Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 under visible light illumination performed by Fast Scanning Nano Hard X-ray Fluorescence Imaging revealed the migration and irreversible phase separation of halide ions into micro-meter sized clusters.