Modeling Anomalous Hysteresis in Perovskite Solar Cells

TLDR

Organic–inorganic lead halide perovskites uniquely combine electronic and ionic transport, making their optoelectronic behavior critical to device optimization and to understanding limitations of perovskite solar cells. A numerical drift‑diffusion model shows that hysteresis in current–voltage curves arises only when both ion migration and electronic charge traps—acting as recombination centers—are included, with trapped carriers recombining with bias‑dependent free carriers. The study demonstrates that decreasing either mobile ionic species or interfacial carrier trapping eliminates hysteresis, offering a clear research target that reconciles prior conflicting observations.

Abstract

Organic–inorganic lead halide perovskites are distinct from most other semiconductors because they exhibit characteristics of both electronic and ionic motion. Accurate understanding of the optoelectronic impact of such properties is important to fully optimize devices and be aware of any limitations of perovskite solar cells and broader optoelectronic devices. Here we use a numerical drift-diffusion model to describe device operation of perovskite solar cells. To achieve hysteresis in the modeled current–voltage characteristics, we must include both ion migration and electronic charge traps, serving as recombination centers. Trapped electronic charges recombine with oppositely charged free electronic carriers, of which the density depends on the bias-dependent ion distribution in the perovskite. Our results therefore show that reduction of either the density of mobile ionic species or carrier trapping at the perovskite interface will remove the adverse hysteresis in perovskite solar cells. This gives a clear target for ongoing research effort and unifies previously conflicting experimental observations and theories.