Exciton Binding Energy of MAPbI3 Thin Film Elucidated via Analysis and Modeling of Perovskite Absorption and Photoluminescence Properties Using Various Methodologies

This work presents spectroscopic investigations of methylammonium lead iodide, MAPbI3, a perovskite thin film, with a focus on elucidating the exciton binding energy of the semiconductor via various approaches in modeling of absorption and photoluminescence spectroscopic data collected in the 150–293 K temperature range. These include the application of modified versions of Elliott's formula to reconstruct steady-state absorption of the semiconductor in the spectral range of the bandgap edge, validated by conjunction with outcomes from transient absorption spectroscopy, and application of numerous variations of the Arrhenius equation to model temperature-induced broadening of the excitonic absorption band and temperature-dependent changes in intensity of photoluminescence emission spectra. All these approaches were simultaneously applied on the spectroscopic data acquired on the same MAPbI3 sample and provide a more comprehensive image of how the value of exciton binding energy depends on the determination methodology. This work demonstrates that after excluding outliers originating most likely from the application of inappropriate fitting models, the exciton binding energy falls within the narrow 7–17 meV energetic range. This study shows that better agreement between different methods of determination of exciton binding energy from analysis of absorption and photoluminescence spectra could be achieved if correct fitting models are applied, and other variables, as for example sample aging, are excluded.