Advanced Characterization of Perovskite Thin Films for Solar Cell Applications Using Time-Resolved Microwave Photoconductivity and Time-Resolved Photoluminescence

Abstract

Thanks to their direct band-gap, high absorption coefficient, low manufacturing cost, and relative abundance of component materials, perovskite materials are strong candidates for the next generation of photovoltaic devices. However, their complex photochemistry and photophysics are hindering their development. This is due, in part, to the complex charge carrier recombination pathways in these materials, as well as their instability during measurements. Here, a new characterization methodology is detailed that allows the measurement, with high certainty, of the intrinsic parameters of a single perovskite sample, such as the trap state concentration and carrier mobilities. This methodology is based on a combination of time-resolved microwave photoconductivity (TRMC) and time-resolved photoluminescence (TRPL) spectroscopy. Compared to TRPL only, this methodology is faster, does not lead to significant changes in the perovskite properties over time, and increases the certainty of the parameters retrieved. Using this methodology, green solvent systems are studied to replace the traditional harmful solvents usually used when spin–coating perovskites. Although devices made using the greener solvents presented lower efficiencies, TRMC and TRPL measurements highlighted that the perovskites made with these solvents can achieve the same performance compared to the traditional solvent system.