Thioalkyl-Substituted Benzothiadiazole Acceptors: Copolymerization with Carbazole Affords Polymers with Large Stokes Shifts and High Solar Cell Voltages

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• 作者：Abby Casey ; Raja Shahid Ashraf ; Zhuping Fei ; Martin Heeney
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：April 8, 2014
• 年：2014
• 卷：47
• 期：7
• 页码：2279-2288
• 全文大小：438K
• 年卷期：v.47,no.7(April 8, 2014)
• ISSN：1520-5835

文摘

Copolymers of carbazole and 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (dTBT) incorporating thioalkyl (鈭扴R) and alkoxy (鈭扥R) solubilizing groups on the 2,1,3-benzothiazdiazole (BT) unit are synthesized and compared. The introduction of 鈭扴R and 鈭扥R groups onto the BT unit of the polymer was found to have different effects on the electronic properties of the polymers as well as the conformation of the polymer backbone. Large conformational changes between the ground state (GS) and excited state (ES) geometries of the polymers with 鈭扴R groups led to very large Stokes shifts of up to 224 nm. The polymer with 鈭扥R groups was found to have approximately double the photovoltaic efficiency at 4% compared to the polymers with 鈭扴R groups (PCE 2%). However, polymers with 鈭扴R groups were found to give very high open circuit voltages (V_OC) of over 1 V. Changing the 鈭扴R chain length from ethyl to dodecyl was found to have little influence on the solar cell performance of the polymer or the magnitude of the Stokes shift.