Nanoscale Heterogeneity in CsPbBr3 and CsPbBr3:KI Perovskite Films Revealed by Cathodoluminescence Hyperspectral Imaging

The nanoscale morphology of solar cell materials strongly affects their performance. We report direct evidence for the existence of multiple length scales of heterogeneity in halide perovskites such as CsPbBr3 and CsPbBr3:KI Contrary to the general notion of two distinct phases, our study suggests the presence of multiple phases in mixed halide perovskites. Highly spatially resolved (approximate to 50 nm) cathodoluminescence maps reveal that the length scale of heterogeneity is composition-dependent: smaller (approximate to 200 nm) for CsPbBr3 and larger (approximate to 500-1000 nm) for CsPbBr3:KI. Moreover, these nano-/micro-scale heterogeneities exist both laterally and vertically in mixed halides and correlate with high densities of carrier traps and fast trap-assisted recombination. The observed heterogeneities also lead to reduced power conversion efficiency of solar cells, higher hysteresis loss, and faster degradation. These insights argue for advanced nanoscale characterization of halide perovskites to guide reduction of heterogeneity and so improve device performance and stability.

Automated summary

The nanoscale morphology of solar cell materials significantly affects their performance, with studies showing the presence of multiple length scales of heterogeneity in mixed halide perovskites. These heterogeneities impact the efficiency, hysteresis loss, and degradation of solar cells, highlighting the need for advanced nanoscale characterization to improve device performance and stability.