The Impact of Mobile Ions on the Steady-State Performance of Perovskite Solar Cells
Mobile ions in perovskite solar cells induce many unique transient phenomena, while their influence under steady state, the primary operating condition, has received little attention. Therefore, in this work, we employ ionic-drift diffusion models to assess how the steady-state distribution of mobile ions affects the photogenerated carrier collection and their redistribution due to dopants and energy band alignment. We demonstrate that mobile ions can transform the carrier transport mechanism from a combination of drift and diffusion to transport by diffusion only, which only impacts the device efficiency if the carrier mobility-lifetime product is limited due to increased transport losses and changed recombination dynamics. A high concentration of dopants is also required in perovskite devices for such doping to have a measurable impact, while the energy alignment of the transport layers, on the other hand, can in principle result in a doping-like effect, which generally causes adverse consequences for cell efficiency.