Photosciences and Photonics Section, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695 019 Kerala, India.
Academy of Scientific and Innovative Research (AcSIR), CSIR-Human Resource Development Centre, Ghaziabad, Uttar Pradesh 201 002, India.
J Phys Chem B. 2021 Jan 14;125(1):231-239. doi: 10.1021/acs.jpcb.0c08590. Epub 2020 Dec 28.
Singlet fission (SF) improves the power conversion efficiency of optoelectronic devices by converting high-energy photons into two triplet excitons. SF dynamics and efficiency (Φ) are controlled by various factors. Here, the effect of planarity and length of the bridge in pentacene dimers on the intramolecular SF (iSF) process was investigated by synthesizing the dimers connected by bridges having fluorene (-, planar), methyl-substituted biphenyl (-, twisted), and diphenyl acetylene (-, longer) groups and characterizing their excited-state relaxation dynamics using nanosecond and femtosecond pump-probe spectroscopy. Transient absorption studies reveal that iSF dynamics of - having a planar bridge are ∼787 times faster (187 ps) and exhibit higher Φ (198%) by feasible electronic coupling, compared to - possessing a twisted bridge showing a low Φ of ∼16%. However compared to -, iSF dynamics of - with an increase of bridge length are slower by an order (1.09 ns) and show comparable Φ of 185% through extended conjugation. Thus, the planarity and length of the bridge in pentacene dimers control the rate and efficiency of the iSF process.
单重态裂变 (SF) 通过将高能光子转化为两个三重态激子来提高光电设备的能量转换效率。SF 动力学和效率 (Φ) 受各种因素控制。在这里，通过合成由具有芴 (-, 平面)、甲基取代联苯 (-, 扭曲) 和二苯乙炔 (-，更长) 基团的桥连接的二聚体，研究了苝二聚体中桥的平面性和长度对分子内 SF (iSF) 过程的影响，并使用纳秒和飞秒泵浦探针光谱法对其激发态弛豫动力学进行了表征。瞬态吸收研究表明，具有平面桥的 - 的 iSF 动力学速度快约 787 倍（187 ps），通过可行的电子耦合表现出更高的 Φ（198%），而具有扭曲桥的 - 的 Φ 较低，约为 16%。然而，与 - 相比，桥长增加的 - 的 iSF 动力学速度慢一个数量级（1.09 ns），并通过扩展共轭表现出相当的 Φ 为 185%。因此，苝二聚体中桥的平面性和长度控制着 iSF 过程的速率和效率。
