Syntheses and Photovoltaic Properties of Narrow Band Gap Donor鈥揂cceptor Copolymers with Carboxylate-Substituted Benzodithiophene as Electron Acceptor Unit

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• 作者：Kosuke Shibasaki ; Kenichi Tabata ; Yohei Yamamoto ; Takeshi Yasuda ; Masashi Kijima
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：August 12, 2014
• 年：2014
• 卷：47
• 期：15
• 页码：4987-4993
• 全文大小：389K
• ISSN：1520-5835

文摘

Stille-coupling of carboxylate-substituted dibrominated benzodithiophene (BDTC) with 2,5-distannylthieno[3,4-b]thiophene gave novel donor鈥揳cceptor type alternating copolymers, PBDTC-TT, where BDTC works as an electron-accepting unit in the polymers. They showed broad absorption bands from 500 nm to the near-infrared region, optical band gap (E_g) about 1.5 eV, small 蟺-stacking distance (3.6 脜), and good thermal stability. The hole mobilities of PBDTC-TT determined from performance of their organic field-effect transistors were 3.1鈥?.9 脳 10^鈥? (cm² V^鈥? s^鈥?). The bulk heterojunction (BHJ) solar cells were fabricated with configuration of ITO/PEDOT:PSS/polymer:PC₇₀BM/LiF/Al. A PBDTC-TT device exhibited photocurrent response upon exposure to light with wavelength of 300鈥?00 nm and incident photon to current conversion efficiency over 40% in the range of 400鈥?50 nm. The power conversion efficiency of the best-performed device reached 3.03% with short-circuit current density of 12.54 mA cm^鈥?, fill factor of 0.48, and open circuit voltage of 0.51 V under illumination of AM 1.5 G/100 mW cm^鈥?. These results show that the BDTC unit can behave as an electron accepting building block for donor鈥揳cceptor type narrow band gap polymers, and these types of polymers can be used as a donor material in the active layer for BHJ photovoltaic cells.