Theoretical Study of Torsional Disorder in Poly(3-alkylthiophene) Single Chains: Intramolecular Charge-Transfer Character and Implications for Photovoltaic Properties

被引:24
作者
Bjorgaard, Josiah A. [1 ]
Kose, Muhammet E. [2 ]
机构
[1] N Dakota State Univ, Dept Chem & Biochem, Fargo, ND 58108 USA
[2] TUBITAK Natl Metrol Inst, TR-41470 Gebze, Kocaeli, Turkey
基金
美国国家科学基金会;
关键词
CONJUGATED POLYMERS; FILMS; POLYTHIOPHENES; ABSORPTION; TRANSITION; OLIGOMERS; LENGTH;
D O I
10.1021/jp401521j
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The role of polymer chain morphology on the optoelectronic properties of polythiophenes is an ongoing investigation with the promise of improving organic photovoltaic performance. Chain morphology is predominantly affected by torsional disorder, which causes localization of holes and electrons in the conjugated backbone. Using the model compound oligo(3-methylthiophene), torsionally disordered oligomers were created to compare with a trans-planar oligomer such as found in crystalline poly(3-hexylthiophene). Low lying electronic excitations are calculated using TD-HF and TD-DFT with various long-range corrected functionals. Probability densities of electron and hole were constructed from natural transition orbitals, giving insight into localization and electron-hole overlap. Overlap is found to be substantially higher in disordered oligomers, indicating a stronger Coulombic interaction between electron and hole. Results suggest that improved photovoltaic performance with increased crystallinity is partially explained by stronger light absorption in crystalline polymers and a higher barrier to charge separation in disordered polymers.
引用
收藏
页码:3869 / 3876
页数:8
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