Gu Qinying, Gorgon Sebastian, Romanov Alexander S, Li Feng, Friend Richard H, Evans Emrys W
Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
Shanghai Artificial Intelligence Laboratory, Shanghai, 200232, P. R. China.
Adv Mater. 2024 Jul;36(30):e2402790. doi: 10.1002/adma.202402790. Epub 2024 Jun 16.
Spin triplet exciton formation sets limits on technologies using organic semiconductors that are confined to singlet-triplet photophysics. In contrast, excitations in the spin doublet manifold in organic radical semiconductors can show efficient luminescence. Here the dynamics of the spin allowed process of intermolecular energy transfer from triplet to doublet excitons are explored. A carbene-metal-amide (CMA-CF) is employed as a model triplet donor host, since following photoexcitation it undergoes extremely fast intersystem crossing to generate a population of triplet excitons within 4 ps. This enables a foundational study for tracking energy transfer from triplets to a model radical semiconductor, TTM-3PCz. Over 74% of all radical luminescence originates from the triplet channel in this system under photoexcitation. It is found that intermolecular triplet-to-doublet energy transfer can occur directly and rapidly, with 12% of triplet excitons transferring already on sub-ns timescales. This enhanced triplet harvesting mechanism is utilized in efficient near-infrared organic light-emitting diodes, which can be extended to other opto-electronic and -spintronic technologies by radical-based spin control in molecular semiconductors.
自旋三重态激子的形成对局限于单重态-三重态光物理的有机半导体技术构成了限制。相比之下，有机自由基半导体中自旋双重态流形内的激发可以表现出高效的发光。在此，我们探索了从三重态激子到双重态激子的分子间能量转移这一自旋允许过程的动力学。一种卡宾-金属-酰胺（CMA-CF）被用作模型三重态供体主体，因为光激发后它会经历极快的系间窜越，在4皮秒内产生三重态激子群体。这使得对追踪从三重态到模型自由基半导体TTM-3PCz的能量转移进行基础研究成为可能。在光激发下，该系统中超过74%的自由基发光源自三重态通道。研究发现分子间三重态到双重态的能量转移可以直接且快速地发生，12%的三重态激子已经在亚纳秒时间尺度上发生了转移。这种增强的三重态俘获机制被用于高效近红外有机发光二极管中，通过分子半导体中基于自由基的自旋控制，它可以扩展到其他光电子和自旋电子技术。
