A New Approach to Characterize Charge Transport and Hysteresis in Perovskite Solar Cells

TL;DR

This paper introduces an analytical charge transport model for perovskite solar cells that integrates experimental impedance spectroscopy data, revealing new insights into hysteresis and transport dynamics under various electrical excitations.

Contribution

The study develops a fully analytical model that captures charge transport and hysteresis in PSCs using experimental data, including large amplitude sinusoidal excitations, without relying on inductive elements.

Findings

Large sinusoidal excitations reveal transition from capacitive to inductive-like responses.

The model accurately simulates hysteresis and electrical behavior under different voltages.

Experimental data combined with the model provides new insights into charge transport mechanisms.

Abstract

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology, already achieving efficiencies surpassing 25%. However, effects such as hysteresis are commonly observed due to the interplay of ionic and electronic transport occurring over different timescales. Despite the widespread use of impedance spectroscopy (IS), physical interpretation in PSCs is specially challenging due to memory effects. In this study, we focus on integrating experimental data with an analytical device transport model. The PSCs under investigation were fabricated using a Cs$_{0.17}$FA$_{0.83}$Pb(I$_{0.83}$Br$_{0.17}$)$_3$ active layer between Nb$_2$O$_5$/TiO$_2$ (compact/mesoporous) and Spiro-OMeTAD. Our fully analytical charge transport model incorporates independent charge transport channels, enabling the correlation of experimental observations in both dark and under illumination. We employed IS together with various voltammetry techniques to reveal the dynamics of the transport processes, including voltage pulses and both small and large amplitude sinusoidal excitations. Although small perturbations are commonly used in IS, our findings demonstrate that large sinusoidal excitation provides new valuable insights in the transition from capacitive to inductive-like responses. The proposed model based purely on charge trapping and generation effectively captures device behavior under both small and large voltages without inductive elements, validated through accurate simulations of hysteresis and other electrical phenomena.