Discerning Rise Time Constants to Quantify Charge Carrier Extraction in Perovskite Solar Cells

Abstract

Abstract The small-perturbation analysis of perovskite solar cells (PSCs) highlights a fundamental conundrum - while time domain measurements yield two time constants corresponding to the rise and subsequent decay of the photovoltage or photocurrent, the corresponding frequency domain methods only yield one time constant from the analysis of the imaginary part of the transfer function. To solve this problem, we propose a modification of the frequency domain transfer function that focusses on the transition of its real part to negative values at high frequencies. After verification using drift-diffusion simulations and equivalent circuit analysis, the application of the method to experimental intensity-modulated photovoltage spectroscopy data of a PSC allows calculation of the hidden rise time constant, showing a good agreement with rise time constants obtained from transient photovoltage measurements. The calculated rise time constants are indicators of the charge extraction efficiency of the contacts, that determines short circuit and low-bias recombination losses.