Winfield Jessica M, Van Vooren Antoine, Park Moo-Jin, Hwang Do-Hoon, Cornil Jérôme, Kim Ji-Seon, Friend Richard H
Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
J Chem Phys. 2009 Jul 21;131(3):035104. doi: 10.1063/1.3177327.
Quantum-chemical calculations performed on poly[2,7-(9,9-di-n-octylfluorene)(1-x)-co-4,7-(2,1,3-benzothiadiazole)(x)] copolymers (0 < or = x < or = 0.5) show that the lowest unoccupied molecular orbital is always highly localized on the benzothiadiazole (BT) units while the highest occupied molecular orbital is delocalized over the whole chain. Chains with a low BT content are characterized by a reduced oscillator strength of the lowest optical transition and by an increased charge-transfer character of the exciton. These results are supported experimentally by a blueshift of the lowest energy absorption band upon reduction in the BT ratio, lower photoluminescence efficiency, longer excited state lifetimes, and greater solvent dependence of the emission properties.
对聚[2,7-(9,9-二正辛基芴)(1 - x)-co - 4,7-(2,1,3 - 苯并噻二唑)(x)]共聚物（0≤x≤0.5）进行的量子化学计算表明，最低未占分子轨道总是高度定域在苯并噻二唑（BT）单元上，而最高占分子轨道则在整个链上离域。BT含量低的链的特征在于最低光学跃迁的振子强度降低以及激子的电荷转移特性增加。这些结果在实验上得到了支持，即随着BT比例降低，最低能量吸收带发生蓝移、光致发光效率降低、激发态寿命延长以及发射特性对溶剂的依赖性更大。
