Theoretical characterization on photoelectric properties of benzothiadiazole- and fluorene-based small molecule acceptor materials for the organic photovoltaics

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• 作者：Mingyue Sui ; Shuangbao Li ; Qingqing Pan ; Guangyan Sun…
• 关键词：Benzothiadiazole ; and fluorene ; based ; Density functional theory ; Organic photovoltaic cells ; Small molecule acceptor
• 刊名：Journal of Molecular Modeling
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：23
• 期：1
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Computer Applications in Chemistry; Molecular Medicine; Computer Appl. in Life Sciences; Characterization and Evaluation of Materials; Theoretical and Computational Chemistry;
• 出版者：Springer Berlin Heidelberg
• ISSN：0948-5023
• 卷排序：23

文摘

The upper efficiency of heterojunction organic photovoltaics depends on the increased open-circuit voltage (V_oc) and short-circuit current (J_sc). So, a higher lowest unoccupied molecular orbital (LUMO) level is necessary for organic acceptor material to possess higher V_oc and more photons absorbsorption in the solar spectrum is needed for larger J_sc. In this article, we theoretically designed some small molecule acceptors (2∼5) based on fluorene (F), benzothiadiazole, and cyano group (CN) referring to the reported acceptor material 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile (1), the crucial parameters affecting photoelectrical properties of compounds 2∼5 were evaluated by the density functional theory (DFT) and time dependent density functional theory (TDDFT) methods. The results reveal that compared with 1, 3 and 4 could have the better complementary absorption spectra with P3HT, the increased LUMO level, the improved V_oc, and the decreased electronic organization energy (λ_e). From the simulation of transition density matrix, it is very clear that the excitons of molecules 3 and 4 are easier to separate in the material surface. Therefore, 3 and 4 may become potential acceptor candidates for organic photovoltaic cells. In addition, with the increased number of CN, the optoelectronic properties of the molecules show a regular change, mainly improve the LUMO level, energy gap, V_oc, and absorption intensity. In summary, reasonably adjusting CN can effectively improve the photovoltaic properties of small molecule acceptors.