Local Background Hole Density Drives Nonradiative Recombination in Tin Halide Perovskites

Abstract

We use multimodal microscopy to study carrier recombination in semiconducting tin halide perovskite films based on PEA(0.2)FA(0.8)SnI(3) (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 PEA(0.2)FA(0.8)SnI(3) films exhibit large hole doping concentrations of p(0) approximate to 10(19) cm(-3), which is reduced to p(0) approximate to 10(16) cm(-3) after SnF2 treatment. While it is well-known that the radiative recombination rates are increased with p(0), we reveal that the nonradiative rate is also increased. We find that p-type regions in untreated PEA(0.2)FA(0.8)SnI(3) films are centers for nonradiative recombination, which are diminished in films with p(0) approximate to 10(16) cm(-3). We discover significant PL heterogeneity even in PEA(0.2)FA(0.8)SnI(3) films with moderate dopant levels, suggesting that new strategies to eliminate deleterious defects in PEA(0.2)FA(0.8)SnI(3) must be developed.