Fei Xian, Zhang San, Zhai Dong, Wang Zhiwei, Lin Jin-Liang, Xiao Qi, Sun Chun-Lin, Deng Weiqiao, Zhang Chunfeng, Hu Wenping, Zhang Hao-Li
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University Lanzhou 730000 China
National Laboratory of Solid State Microstructures, Collaborative Innovation Centre of Advanced Microstructures, School of Physics, Nanjing University Nanjing 210093 China
Chem Sci. 2022 Jul 27;13(34):9914-9920. doi: 10.1039/d2sc00263a. eCollection 2022 Aug 31.
Singlet exciton fission (SF) is believed to have the potential to break the Shockley-Queisser limit for third-generation solar cell devices, so it has attracted great attention. Conventional linear acene based SF materials generally suffer from low triplet energy and poor photostability. We report herein two flavanthrene derivatives, EH-Fla and TIPS-Fla, as new photostable singlet exciton fission materials. These N-doped two-dimensional angular fused acenes have three sets of aromatic Clar sextets, making them significantly more stable than linear acenes with only one sextet. Time-resolved spectroscopy characterization reveals that the SF process occurs in the polycrystalline films of EH-Fla and TIPS-Fla, with maximal triplet yields of 32% and 159%, respectively. The SF processes of these two molecules are mediated by excimer states. In EH-Fla, the low-lying excimer prevents the SF process from occurring effectively, resulting in a low triplet yield. In contrast, the excimer state in TIPS-Fla is mixed with strong CT coupling, which prompts efficient SF and results in a high triplet yield. Our results show that flavanthrene is a promising SF chromophore for photoenergy conversion applications, while a fine-tune of the intermolecular interaction is crucial for achieving high SF efficiency.
单线态激子裂变（SF）被认为有潜力突破第三代太阳能电池器件的肖克利-奎塞尔极限，因此备受关注。传统的基于线性并苯的SF材料通常存在三重态能量低和光稳定性差的问题。我们在此报告两种芘蒽衍生物，EH-Fla和TIPS-Fla，作为新型光稳定的单线态激子裂变材料。这些氮掺杂的二维角稠并苯有三组芳香族克莱尔六隅体，使其比仅有一个六隅体的线性并苯稳定得多。时间分辨光谱表征表明，SF过程发生在EH-Fla和TIPS-Fla的多晶薄膜中，最大三重态产率分别为32%和159%。这两个分子的SF过程由准分子态介导。在EH-Fla中，低能准分子阻止了SF过程的有效发生，导致三重态产率较低。相比之下，TIPS-Fla中的准分子态与强电荷转移耦合混合，这促使了高效的SF并导致高三重态产率。我们的结果表明，芘蒽是用于光能转换应用的有前景的SF发色团，而分子间相互作用的微调对于实现高SF效率至关重要。
