Analysis of Photocarrier Dynamics at Interfaces in Perovskite Solar Cells by Time-Resolved Photoluminescence

Abstract

The power conversion efficiency of perovskite solar cells is drastically affected by photocarrier dynamics at the interfaces. Experimental measurements show quenching of the photoluminescence (PL) signal from the perovskite layer when it is capped with a hole transport medium (HTM). Furthermore, time-resolved PL (TRPL) data show a faster decay of the PL signal in the presence of the perovskite/HTM interface. The experimental decay is usually fitted using one or two exponential functions with an incomplete physical picture. In this work, an extensive model is used to extract the key physical parameters characterizing carrier dynamics in the bulk and at the interfaces. The decay of the TRPL signal is calculated in the presence of both defect-assisted recombination (Shockley Read Hall) and band-to-band radiative recombination where carrier extraction/recombination at the interfaces is described by interface recombination velocities. By proper curve fitting of the modeling results and the measured TRPL signal, meaningful optoelectronic parameters governing photophysical processes in mixed halide perovskite thin films and single crystals are extracted. Furthermore, a sensitivity analysis to assess the contribution of these parameters on TRPL kinetics is also performed. Notably, the inclusion of the diffusion and surface recombination velocity at the interfaces allows to obtain the important physical parameters that govern the TRPL kinetics and improve the conformity of fits to experiments.