Mencaroni Letizia, Carlotti Benedetta, Elisei Fausto, Marrocchi Assunta, Spalletti Anna
Department of Chemistry Biology and Biotechnology and CEMIN, University of Perugia via elce di sotto n. 8, 06123 Perugia Italy
Chem Sci. 2022 Feb 2;13(7):2071-2078. doi: 10.1039/d1sc07175k. eCollection 2022 Feb 16.
In this study, we report strong experimental evidence for singlet fission (SF) in a new class of fluorene-based molecules, exhibiting two-branched donor-acceptor structures. The time-resolved spectroscopic results disclose ultrafast formation of a double triplet state (occurring in few picoseconds) and efficient triplet exciton separation (up to 145% triplet yield). The solvent polarity effect and the role of intramolecular charge transfer (ICT) on the SF mechanism have been thoroughly investigated with several advanced spectroscopies. We found that a stronger push-pull character favors SF, as long as the ICT does not act as a trap by opening a competitive pathway. Within the context of other widely-known SF chromophores, the unconventional property of generating high-energy triplet excitons ( 2 eV) SF makes these materials outstanding candidates as photosensitizers for photovoltaic devices.
在本研究中，我们报告了一类新型芴基分子中发生单线态裂变（SF）的有力实验证据，这类分子具有双分支供体-受体结构。时间分辨光谱结果揭示了双三重态的超快形成（在几皮秒内发生）以及高效的三重态激子分离（三重态产率高达145%）。利用几种先进的光谱技术，对溶剂极性效应和分子内电荷转移（ICT）在SF机制中的作用进行了深入研究。我们发现，只要ICT不会通过开启竞争途径而成为陷阱，更强的推挽特性就有利于SF。在其他广为人知的SF发色团的背景下，SF产生高能三重态激子（2 eV）的非常规特性使这些材料成为光伏器件光敏剂的杰出候选者。
