Interpreting Halide Perovskite Semiconductor Photoluminescence Kinetics

Abstract

Drawing from both experimental data and simulation, we highlight best practices for fitting time-resolved photoluminescence (TRPL) decays of halide perovskite semiconductors, which are now widely studied for applications in photovoltaics and light-emitting diodes (LEDs). First, at low excitation intensities, high-quality perovskites often show pseudo-first-order kinetics, consistent with classic minority carrier lifetimes. Second, multiexponential decays, frequently observed at low excitation intensities, often have significant contributions from spatial heterogeneity. We recommend fitting such decays with stretched exponentials, where the stretching factor (β) can be used to characterize the heterogeneity of the local lifetime distribution. Third, PL decay kinetics can depend on the excitation wavelength. We discuss how penetration depth, carrier diffusion, and surface recombination affect measurements and make recommendations for choosing experimental parameters suited to the question at hand. Accounting for these factors will provide a more reliable and physical interpretation of carrier recombination and better understanding of nonradiative losses in perovskite semiconductors.

Charge Transfer Kinetics in Halide Perovskites: On the Constraints of Time-Resolved Spectroscopy Measurements

“…For this, a suitable reference sample must be used, that is assumed to have properties similar to those of the CTL/perovskite assembly under investigation. 1 τ C T = 1 τ C T L / p e r o v s k i t e − 1 τ p e r o v s k i t e When significant deviations are observed from the ideal exponential behavior (as in eq ), the use of a stretched exponential function as described by eq can be employed to analyze the PL decay. This evaluation method includes spatial inhomogeneities in the films, and all these processes can be described by a distribution of the rate constant . The deviation from ideality is described by a β parameter (0 < β < 1): I false( t false) = ∑ i = 1 n A i e x p false( prefix− t τ normali false) β i To showcase the importance of the chosen data evaluation method, we determined the charge transfer rate constant for a TiO 2 /perovskite data set with the previously outlined methods.…”

“…This evaluation method includes spatial inhomogeneities in the films, and all these processes can be described by a distribution of the rate constant. 96 The deviation from ideality is described by a β parameter (0 < β < 1): To showcase the importance of the chosen data evaluation method, we determined the charge transfer rate constant for a TiO 2 /perovskite data set with the previously outlined methods. Other representative TRPL traces (triexponential and stretched exponential fitting), together with the fitted curve, are shown in Figure S1 .…”