Perovskite light-emitting diodes are promising for next-generation lighting and displays because of their high colour purity and performance¹. Although the management of singlet and triplet excitons is fundamental to the design of efficient organic light-emitting diodes, the nature of how excitons affect performance is still not clear in perovskite^2,3,4 and quasi-two-dimensional (2D) perovskite-based devices^5,6,7,8,9. 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. The external quantum and current efficiencies of our green (527 nm) devices reached 12.4% and 52.1 cd A⁻¹, respectively.

钙钛矿发光二极管具有高色纯度和高性能，因此有望用于下一代照明和显示器¹。尽管单线态和三线态激子的管理对于高效有机发光二极管的设计至关重要，但是在钙钛矿^2、3、4和准二维（2D）钙钛矿中，激子如何影响性能的本质仍然不清楚。基于设备的^5,6,7,8,9。在这里，我们表明三重态激子是绿色准2D钙钛矿装置中有效发射的关键，而有机阳离子对三重态的猝灭是主要的损失途径。在基于甲ami溴化铅的准2D钙钛矿中使用具有高三重态能级的有机阳离子（苯乙基铵），可有效收获三胞胎。此外，我们表明三重态向单重态的上转换可能发生，使得电激发子的100％收获成为可能。我们的绿色（527 nm）器件的外部量子效率和电流效率分别达到12.4％和52.1 cd A ^-1。