Optimization of recombination region within inorganic perovskite light emitting diodes

Recent advances in metal halide perovskite-based LEDs have included high brightness, extended lifetimes, and excellent color saturation in comparison with other thin film light sources such as OLEDs. We have shown that many of these properties can be traced to nanoscale sub-phase formation within the larger perovskite matrix, which leads to exciton self-trapping. However, since such phase formation modifies carrier mobility, a significant challenge in per-LEDs is optimizing device design such that the driving voltage, sensitive of recombination zone formation and position within the emitting layer, is overcome. In this work we examine the use of various organic layers, such as poly-TPD, in barrier formation and recombination zone stability. We show that interface preparation between the perovskite and transport layers can play a major role in barrier formation. Focusing on the correlation of brightness and efficiency with device structure modification, we demonstrate that optimized carrier balance can allow for maintained efficiency over a wide range of driving voltages and brightnesses.