Light management for perovskite light-emitting diodes

Perovskite light-emitting diodes (LEDs) have reached external quantum efficiencies of over 20% for various colours, showing great potential for display and lighting applications. Despite the internal quantum efficiencies of the best-performing devices already approaching unity, around 80% of the internally generated photons are trapped in the devices and lose energy through a variety of lossy channels. Significant opportunities for improving efficiency and maximizing photon extraction lie in the effective management of light. In this Review we analyse light management strategies based on the intrinsic optical properties of the perovskite materials and the extrinsic properties related to device structures. These approaches should allow the external quantum efficiencies of perovskite LEDs to substantially exceed the conventional limits of planar organic LED devices. By revisiting lessons learned from organic LEDs and perovskite solar cells, we highlight possible directions of future research towards perovskite LEDs with ultrahigh efficiencies. This Review analyses the mechanisms of light extraction from perovskite light-emitting diodes and suggests new approaches towards ultrahigh electroluminescence efficiencies.