Probing Lateral and Vertical Heterogeneity in Halide Perovskite Semiconductors— From Photoluminescence to Sub-Diffraction Carrier Dynamics

Even high-performance formulations of halide perovskite semiconductors can exhibit complex spatial heterogeneity on multiple characteristic length scales. These heterogeneities range from compositional fluctuations and thin film grain and sub-grain structure on the multi-micron to sub-diffraction length scale, to vertical variations in carrier lifetimes due to surface recombination at the bottom and top contacts. We combine multimodal probes, ranging from hyperspectral microscopy and multi-wavelength photoluminescence, to sub-diffraction dynamic electrical scanning probe microscopy under photoexcitation to probe spatial variations in lateral and vertical carrier dynamics. We apply these techniques to a range of different surface passivation, growth strategies, and compositions, and we show how different methods influence carrier recombination lifetimes, while also pointing the way towards processing improvements that could lead to higher performance and improved stability.