Unraveling the role of excitons in the near ideal performance of perovskite light emitting diodes

Abstract: Recent reports indicate that perovskite based light emitting diodes (LEDs) have achieved an external quantum efficiency (EQE) of 32% - rather an internal quantum efficiency close to 100%. Much of this improved performance is attributed to the role of excitons. While the experimental trends are encouraging, the recombination parameters estimated through extensive curve-fitting of photoluminescence (PL) transients are often not amenable to reasonable interpretations. In view of the same, through a detailed analysis of free carrier - exciton dynamics in perovskite optoelectronic materials, here we identify a coherent scheme to unambiguously back extract the relevant parameters. The model predictions compare well with the recent experimental results on perovskite LEDs with record EQE thus quantifying the role of excitons. Importantly, this work identifies a physics aware scheme for the design of experiments tailored towards consistent exploration of underlying physical mechanisms and hence could enable a synergistic optimization of process technology and device performance.