The efficiency of an organic light-emitting diode (OLED) is fundamentally governed by the spin of recombining electron-hole pairs (singlet and triplet excitons), since triplets cannot usually emit light. The singlet-triplet energy gap, a key factor for efficient utilization of triplets, is normally positive. Here we show that in a family of materials with amide donor and carbene acceptor moieties linked by a metal, this energy gap for singlet and triplet excitons with charge-transfer character can be tuned from positive to negative values via the rotation of donor and acceptor about the metal-amide bond. When the gap is close to zero, facile intersystem crossing is possible, enabling efficient emission from singlet excitons. We demonstrate solution-processed LEDs with exceptionally high quantum efficiencies (near-100% internal and >27% external quantum efficiencies), and current and power efficiencies (87 cd/A and 75 lm/W) comparable to, or exceeding, those of state-of-the-art vacuum-processed OLEDs and quantum dot LEDs.

中文翻译：

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基于卡宾金属酰胺的高性能发光二极管

有机发光二极管 (OLED) 的效率从根本上取决于复合电子-空穴对（单重态和三重态激子）的自旋，因为三重态通常不能发光。单线态-三线态能隙是有效利用三线态的关键因素，通常是正的。在这里，我们表明，在具有由金属连接的酰胺供体和卡宾受体部分的一系列材料中，具有电荷转移特性的单线态和三线态激子的这种能隙可以通过供体和受体旋转约金属-酰胺键。当间隙接近于零时，系统间可以轻松交叉，从而实现单线态激子的有效发射。我们展示了具有极高量子效率（接近 100% 内部和 >