Chen Qi, Liu Yiming, Guo Xinyan, Peng Jiang, Garakyaraghi Sofia, Papa Christopher M, Castellano Felix N, Zhao Dahui, Ma Yuguo
Beijing National Laboratory for Molecular Sciences (BNLMS), Center for Soft Matter Science and Engineering, Key Lab of Polymer Chemistry & Physics of Ministry of Education, College of Chemistry , Peking University , Beijing 100871 , China.
Department of Chemistry , North Carolina State University , Raleigh , North Carolina 27695-8204 , United States.
J Phys Chem A. 2018 Aug 23;122(33):6673-6682. doi: 10.1021/acs.jpca.8b05901. Epub 2018 Aug 13.
A heavy-atom-free triplet sensitizer suitable for triplet-triplet annihilation-based photon upconversion was developed from the thermally activated delayed fluorescence (TADF) molecule 4CzPN by covalently tethering a pyrene derivative (DBP) as a triplet acceptor. The triplet exciton produced by 4CzPN is captured by the intramolecular pyrenyl acceptor and subsequently transferred via intermolecular triplet-triplet energy transfer (TTET) to freely diffusing pyrenyl acceptors in toluene. Transient absorption and time-resolved photoluminescence spectroscopy were employed to examine the dynamics of both the intra- and intermolecular TTET processes, and the results indicate that the intramolecular energy transfer from 4CzPN to DBP is swift, quantitative, and nearly irreversible. The reverse intersystem crossing is suppressed while intersystem crossing remains efficient, achieving high triplet yield and long triplet lifetime simultaneously. The ultralong excited state lifetime characteristic of the DBP triplet was shown to be crucial for enhancing the intermolecular TTET efficiency and the subsequent triplet-triplet annihilation photochemistry. It was also demonstrated that with the long triplet lifetime of the tethered DBP, TTET was enabled under low free acceptor concentrations and/or with sluggish molecular diffusion in polymer matrixes.
通过共价连接芘衍生物（DBP）作为三重态受体，从热激活延迟荧光（TADF）分子4CzPN开发出一种适用于基于三重态-三重态湮灭的光子上转换的无重原子三重态敏化剂。4CzPN产生的三重态激子被分子内芘基受体捕获，随后通过分子间三重态-三重态能量转移（TTET）转移到甲苯中自由扩散的芘基受体上。采用瞬态吸收和时间分辨光致发光光谱来研究分子内和分子间TTET过程的动力学，结果表明从4CzPN到DBP的分子内能量转移迅速、定量且几乎不可逆。反向系间窜越受到抑制，而系间窜越仍然有效，同时实现了高三重态产率和长三重态寿命。DBP三重态的超长激发态寿命特性被证明对于提高分子间TTET效率和随后的三重态-三重态湮灭光化学至关重要。还证明了由于连接的DBP具有长三重态寿命，在低自由受体浓度和/或聚合物基质中分子扩散缓慢的情况下也能实现TTET。
