Li Feng, Gillett Alexander J, Gu Qinying, Ding Junshuai, Chen Zhangwu, Hele Timothy J H, Myers William K, Friend Richard H, Evans Emrys W
State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun, 130012, P. R. China.
Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK.
Nat Commun. 2022 May 18;13(1):2744. doi: 10.1038/s41467-022-29759-7.
Organic light-emitting diodes (OLEDs) must be engineered to circumvent the efficiency limit imposed by the 3:1 ratio of triplet to singlet exciton formation following electron-hole capture. Here we show the spin nature of luminescent radicals such as TTM-3PCz allows direct energy harvesting from both singlet and triplet excitons through energy transfer, with subsequent rapid and efficient light emission from the doublet excitons. This is demonstrated with a model Thermally-Activated Delayed Fluorescence (TADF) organic semiconductor, 4CzIPN, where reverse intersystem crossing from triplets is characteristically slow (50% emission by 1 µs). The radical:TADF combination shows much faster emission via the doublet channel (80% emission by 100 ns) than the comparable TADF-only system, and sustains higher electroluminescent efficiency with increasing current density than a radical-only device. By unlocking energy transfer channels between singlet, triplet and doublet excitons, further technology opportunities are enabled for optoelectronics using organic radicals.
有机发光二极管（OLED）的设计必须规避电子-空穴俘获后三线态与单线态激子形成的3:1比例所带来的效率限制。在此，我们展示了诸如TTM-3PCz等发光自由基的自旋性质，其能够通过能量转移直接从单线态和三线态激子中获取能量，随后从双重态激子实现快速且高效的发光。这在一种典型的热激活延迟荧光（TADF）有机半导体4CzIPN中得到了证明，其中三线态的反向系间窜越速度极慢（1微秒时发射率为50%）。自由基与TADF的组合通过双重态通道的发光速度比仅含TADF的可比系统快得多（100纳秒时发射率为80%），并且与仅含自由基的器件相比，随着电流密度的增加，其保持着更高的电致发光效率。通过开启单线态、三线态和双重态激子之间的能量转移通道，利用有机自由基的光电子学有了更多的技术机遇。
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