Light Illumination Induced Photoluminescence Enhancement and Quenching in Lead Halide Perovskite

It has been found that light illumination (soaking) can significantly change the optical and electronic properties of perovskites and the performance of perovskite solar cells. Here using steady state and time‐resolved photoluminescence (PL) techniques, we investigate systematically the effect of light illumination on a well encapsulated CH 3 NH 3 PbI 3 perovskites. Under a continuous constant illumination at low intensity, the PL exhibits either enhancement or constant; dependent on the detrapping rate and density of the defect states in the perovskite which in turn is determined by fabrication methods. Defect curing is attributed to the origin of the PL enhancement. Under a continuous higher intensity illumination, PL quenching is observed with different thresholds relevant to the sample fabrication. This is ascribed to mobile ion accumulation resulting in increased electron/ hole non‐radiative recombination. We confirmed the PL enhancement and quenching under continuous illumination (light soaking) partly originate from the intrinsic contribution of the perovskite, closely correlated to the defect density therefore the fabrication. These findings provide novel insight into the carrier dynamics correlated to the defect trapping and mobile ions which helps to understand the instability of perovskite solar cells.