Local Background Hole Density Drives Nonradiative Recombination in Tin Halide Perovskites

We use multimodal microscopy to study carrier recombination in semiconducting tin halide perovskite films based on PEA0.2FA0.8SnI3 (PEA = phenethylammonium; FA = formamidinium). We use the observation of pseudo-first-order photoluminescence (PL) decay kinetics to establish a method for quantifying the hole dopant level and nonradiative recombination rate constant. We find that untreated PEA0.2FA0.8SnI3 films exhibit large hole doping concentrations of p0 ≈ 1019 cm–3, which is reduced to p0 ≈ 1016 cm–3 after SnF2 treatment. While it is well-known that the radiative recombination rates are increased with p0, we reveal that the nonradiative rate is also increased. We find that p-type regions in untreated PEA0.2FA0.8SnI3 films are centers for nonradiative recombination, which are diminished in films with p0 ≈ 1016 cm–3. We discover significant PL heterogeneity even in PEA0.2FA0.8SnI3 films with moderate dopant levels, suggesting that new strategies to eliminate deleterious defects in PEA0.2FA0.8SnI3 must be developed.