Ionic polarization-induced current–voltage hysteresis in CH ₃NH ₃PbX ₃ perovskite solar cells

Abstract

CH ₃NH ₃PbX 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.

Abstract

The origin of hysteresis remains an open question in lead-halide perovskite solar cells. Here, Meloni et al. investigate the causes of hysteresis using an experimental and computational approach, finding that the observed hysteresis is due to halide ion-vacancy movement in the perovskite.