Ionic polarization-induced current–voltage hysteresis in CH3NH3PbX3 perovskite solar cells

TLDR

Perovskite solar cells based on MAPbX3 achieve efficiencies above 20%, yet the origin of their current–voltage hysteresis remains poorly understood. The study aims to determine the origin of the hysteresis using experimental and computational methods. The authors measured the hysteresis activation energy experimentally and compared it to first‑principles simulations of methylammonium rotation and halide vacancy migration. The results rule out methylammonium rotation as the cause and identify halide ion migration as the mechanism behind the hysteresis.

Abstract

Abstract CH 3 NH 3 PbX 3 (MAPbX 3 ) perovskites have attracted considerable attention as absorber materials for solar light harvesting, reaching solar to power conversion efficiencies above 20%. In spite of the rapid evolution of the efficiencies, the understanding of basic properties of these semiconductors is still ongoing. One phenomenon with so far unclear origin is the so-called hysteresis in the current–voltage characteristics of these solar cells. Here we investigate the origin of this phenomenon with a combined experimental and computational approach. Experimentally the activation energy for the hysteretic process is determined and compared with the computational results. First-principles simulations show that the timescale for MA + rotation excludes a MA-related ferroelectric effect as possible origin for the observed hysteresis. On the other hand, the computationally determined activation energies for halide ion (vacancy) migration are in excellent agreement with the experimentally determined values, suggesting that the migration of this species causes the observed hysteretic behaviour of these solar cells.