Effects of including electron-withdrawing atoms on the physical and photovoltaic properties of indacenodithieno[3, 2-b]thiophene-based donor–acceptor polymers: towards an acceptor design for efficient polymer solar cells. Issue 33 (7th April 2017)

• Record Type: Journal Article
• Authors: Cai, Ping; Xu, Xiaofeng; Sun, Jiangman; Chen, Junwu; Cao, Yong
• Is Part Of: RSC advances. Volume 7:Issue 33(2017)
• Page Start: 20440
• Page End: 20450
• Publication Date: 2017-04-07
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c7ra01049d
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Three new D–A polymers using indacenodithieno[3, 2- b ]thiophene (IDTT) as an electron-rich unit and benzoxadiazole (BO), benzodiathiazole (BT) or difluorobenzothiadiazole (FBT) as an electron-deficient unit were synthesized and applied in solar cells. Abstract : Three new D–A polymersPIDTT-DTBO, PIDTT-DTBT andPIDTT-DTFBT, using indacenodithieno[3, 2- b ]thiophene (IDTT ) as the electron-rich unit and benzoxadiazole (BO ), benzodiathiazole (BT ) or difluorobenzothiadiazole (FBT ) as the electron-deficient unit, were synthesized via a Pd-catalyzed Stille polymerization. The included electron-withdrawing atoms of the acceptor portion were varied between O, S, and F for tailoring the optical and electrochemical properties and the geometry of structures. Their effects on the film topography, photovoltaic and hole-transporting properties of the polymers were thoroughly investigated via a range of techniques. As expected, the stronger electron-withdrawingBO unit affords red-shifted absorption, low-lying HOMO and LUMO levels for the polymerPIDTT-DTBO . However, it depicts lower hole mobility and a less efficient charge collection in the active layer compared to the polymerPIDTT-DTBT . In addition, degradation of the solubility is observed in the fluorinated polymerPIDTT-DTFBT . As a result, a BHJ PSC (ITO/PEDOT:PSS/polymer:PC71 BM/interlayer/Al) fabricated withPIDTT-DTBT attains the best power conversion efficiency (PCE) of 4.91%. These results thus demonstrate the potential effects of electronegative atoms onIDTT -based polymers and the structure–function correlations of such electron-donor materials for efficient PSCs.