Characterization of trap states in perovskite films by simultaneous fitting of steady-state and transient photoluminescence measurements

Abstract

Understanding carrier recombination mechanisms and quantifying recombination dynamics are key to improving the performance of state-of-the-art perovskite solar cells. Here, we present a method to quantify the quality of perovskite thin films using a combination of steady-state and transient photoluminescence measurements. The combined experimental datasets are fitted using a single, general recombination model, from which detailed trap and recombination parameters can be extracted, and the accuracy of the fitted values is estimated. This approach expands the application of photoluminescence measurements to include quantitative evaluation of the most relevant defect characteristics, including trap density, energy level, and carrier capture coefficients. We apply this approach to compare perovskite films of the widely studied methyl-ammonium lead iodide (MAPbI3) with the high performance quadruple-cation, mixed-halide composition Cs0.07Rb0.03(FA0.85MA0.15)0.9Pb(I0.85Br0.15)3. Our quantitative analysis of trap properties in these perovskite films suggests that the superior performance of the quadruple cation films may be due to a greatly reduced electron capture coefficient, rather than a significant reduction in the trap density.