Halide Perovskites, HaPs, present high optoelectronic quality semiconductors, which is remarkable due to their low-temperature solution preparation. Evidence for significant densities of optoelectronically active defects, i.e., with levels in the band gap is contradictory and, especially for single crystals, very low densities have been deduced. These findings led us to propose the occurrence of self-repair of defects. Clarifying these issues, is the defect density indeed unusually low, and is there self-repair, under solar cell working conditions is important both for fundamental understanding of the HaP materials and for guiding us in designing or identifying other materials with such behavior. Here we use high solar cell quality HaPs with systematically varying compositions, to address these questions. Highly specialized electron beam-induced current (EBIC) measurements with and without illumination, as function of bias and/or temperature allow to map and track changes in junction positions and diffusion/ drift lengths. We find that the EBIC profile shape changes and that the diffusion lengths increase as function of supra band gap illumination in the device configuration. The physical origin of the illumination effect is not simply the photogeneration of the carriers as we observed an increase of electron diffusion length with light intensity, which suggests structural electronic rearrangements to screen the increased generated carries. By adding studies of the mobility-lifetime product, photoconductivity, and work function, we arrive at a first description of these, beyond PV, photogenerated changes.
