High efficiency and durability from perovskite–organic hybrid light-emitting diodes

Perovskite light-emitting diodes are promising for next-generation lighting and displays. However, the nature of how excitons affect performance is still not clear in perovskite and quasi-two-dimensional (2D) perovskite-based devices. Here, we show that triplet excitons are key to efficient emission in green quasi-2D perovskite devices and that quenching of triplets by the organic cation is a major loss path. Employing an organic cation with a high triplet energy level (phenylethylammonium) in a quasi-2D perovskite based on formamidinium lead bromide yields efficient harvesting of triplets. Furthermore, we show that upconversion of triplets to singlets can occur, making 100% harvesting of electrically generated excitons potentially possible.