PNNL

Abstract

We use multimodal microscopy to study carrier recombination in semiconducting tin halide perovskite films based on formamidinium (FA) tin (II) triiodide (FASnI3). We use the observation of pseudo-first order photoluminescence decay kinetics to measure the hole carrier density, p0, and we find that untreated FASnI3 films exhibit large hole doping concentrations (p0 ~ 1019 cm-3). Hyperspectral photoluminescence (PL) microscopy shows that films exhibit strong microscale variations in both bandgap and PL intensity. Treatment with SnF2 results in ~1000X lower doping level (p0 ~ 1016 cm-3 ) and a concomitant reduction in the PL heterogeneity. Correlated PL spectroscopy and conductive atomic force microcopy (c-AFM) show that p-type regions in FASnI3 films act as centers for non-radiative recombination, suggesting that further work to eliminate deleterious self p-doping could boost performance