Recombination Pathways in Perovskite Solar Cells

The outstanding optoelectronic properties of metal halide perovskites make them an attractive photovoltaic absorber material and has rapidly culminated in the development of highly efficient perovskite solar cells outperforming many conventional alternatives. However, the device stack still suffers from non-negligible losses induced by various nonradiative recombination processes, which are not fully understood till date. This paper highlights recent findings attempting to understand the nature and origin of nonradiative recombination induced losses within the device stack, as well as the quantification of the magnitude and rates associated with key loss pathways mostly via steady state and transient contactless optical techniques. These studies show that nonradiative recombination processes occurring at interfaces are more dominant than those within the bulk of the perovskite absorber. However, recent findings also show that there remains room for improvement for the suppression of bulk nonradiative recombination. General routes for suppressing recombination processes within the bulk and at interfaces are discussed. Finally, current challenges are presented, which need to be overcome in order to obtain a deeper insight into the nature of defects at surfaces and within the bulk of perovskites, and ultimately enhance the power conversion efficiency of perovskite solar cells toward their thermodynamic efficiency limit.