Fluorinated thienyl-quinoxaline-based D–π–A-type copolymer toward efficient polymer solar cells: synthesis, characterization, and photovoltaic properties

• Published in: Polymer chemistry Vol. 4; no. 11; pp. 3411 - 3418
• Main Authors: Chen, Hsieh-Chih, Chen, Ying-Hsiao, Liu, Chung-Hao, Hsu, Yen-Hao, Chien, Yun-Chen, Chuang, Wei-Ti, Cheng, Chih-Yang, Liu, Chien-Liang, Chou, Shang-Wei, Tung, Shih-Huang, Chou, Pi-Tai
• Format: Journal Article
• Language: English
• Published: 01.01.2013
• Subjects: Copolymers; Density; Fluorination; Nanostructure; Photovoltaic cells; Segments; Self assembly; Solar cells
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/c3py00235g

A tailor-made donor- pi -acceptor copolymer comprising of a medium electron-donating alkylthienyl-benzodithiophene (BDTT) moiety and a strong electron-accepting fluorinated thienyl-quinoxaline (TTFQ) segment with thiophene pi -bridge units has been synthesized by Stille coupling polymerization and thoroughly characterized for use as a p-type semiconducting polymer. The semicrystalline copolymer PBDTT-TTFQ shows a broad visible-near-infrared absorption band with an optical bandgap of 1.67 eV and possesses a relatively low-lying HOMO level at -5.34 eV. In addition, the PBDTT-TTFQ neat film reveals a highly dense fibrillar nanostructure with a certain degree of long-range order, suggesting the nanoscale self-assembly of PBDTT and TTFQ segments. A bulk-heterojunction polymer solar cell based on the blend of 1 : 1 PBDTT-TTFQ:PC sub(71)BM shows an open circuit voltage of 0.75 V, a short circuit current density of 14.6 mA cm super(-2), and a fill factor of 56.1%, achieving a power conversion efficiency of 6.1% under the illumination of AM 1.5G, 100 mW cm super(-2). The results unambiguously indicate that the PBDTT-TTFQ is an auspicious candidate for next-generation solar cell materials.