Subgrain Special Boundaries in Halide Perovskite Thin Films Restrict Carrier Diffusion

Photoluminescence microscopy reveals subgrain special boundaries in FAPbI3 perosvkite thin films that restrict carrier diffusion and serve as nonradiative recombination sites. These subgrain boundaries, which cannot be observed by conventional AFM or SEM measurements of grain-boundary grooves, may explain why the performance of perovskite solar cells has not scaled with apparent grain size.