Triplet Generation Dynamics in Si- and Ge-Bridged Conjugated Copolymers
Triplet Generation Dynamics in Si- and Ge-Bridged Conjugated Copolymers
复制标题
DOI：
10.1021/acs.jpcc.1c09253
复制
发表时间：
2022-01-05
影响因子：
3.7
通讯作者：
Dimitrov, Stoichko D.
中科院分区：
文献类型：
--
作者：
Hernandez, Federico J.;Fei, Zhuping;Dimitrov, Stoichko D.
利用暂态吸收光谱和量子化学计算方法研究了半导体聚合物共轭主链中掺入Si和Ge原子对薄膜和聚合物/富勒烯共混体系激发态动力学的影响。解析了共聚物的单态和三态激子动力学，测得二硫代硅分子的系间交叉时间常数为6.98+/-0.45ps，比二硫代硅分子长近4倍。这一结果表明，重原子效应以外的其他因素控制着共聚物的ISC速率和整体激发态动力学。我们的量子化学计算和基于非绝热极限下电子转移过程的半经典推导的ISC速率估计表明，BuSiDT中ISC时间常数增加的主要驱动因素是二硫硅醚中硅桥联的噻吩类分子的平面性降低和平面外扭转振动增加，导致自旋-轨道耦合增加8.3倍，从而产生更高的ISC速率。在聚合物/富勒烯共混物中，估计了电荷产生率。这项研究的结果表明，在共轭聚合物主链中的桥位引入重原子可以作为一种微调激发态性质的合成策略。
The effect of incorporating Si and Ge atoms in the conjugated backbone of semiconductor polymers is investigated using transient absorption spectroscopy and quantum chemical calculations to uncover the heavy-atom impact on the excited-state dynamics in neat films and polymer/fullerene blends. The singlet and triplet exciton dynamics of the copolymers are resolved and the time constant of intersystem crossing (ISC) of dithienosilole is found to be 6.98 +/- 0.45 ps and nearly 4 times longer than that of dithienogermole. This result indicates that factors other than the heavy-atom effect govern the ISC rates and the overall excited-state dynamics in the copolymers. Our quantum chemical calculations and estimates of the ISC rates based on the semiclassical derivation for the electron-transfer processes in the nonadiabatic limit reveal that the main driver for the increased ISC time constant in BuSiDT is the reduction in planarity and increased torsional out-of-plane vibration of the Si-bridged thiophenes in the dithienosilole compared to the dithienogermole, leading to 8.3 times higher spin-orbit coupling and consequently a higher ISC rate. In the polymer/fullerene blends, charge generation yields are estimated. The results from this study indicate that the incorporation of heavy atoms in a bridge position within the conjugated polymer backbone can be used as a synthetic strategy to fine-tune excited-state properties.