Synthesis and photovoltaic properties of conjugated copolymers with benzo[1,2-b:4,5-b′]dithiophene and thiadiazolo[3,4-c]pyridine moieties

• Published in: European polymer journal Vol. 49; no. 9; pp. 2738 - 2747
• Main Authors: Kang, Huaiyin, Zhao, Bin, Cao, Zhencai, Zhong, Jun, Li, Haohao, Pei, Yong, Shen, Ping, Tan, Songting
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2013; Elsevier
• Subjects: Applied sciences; Benzo[1,2-b:4,5-b′]dithiophene; Conjugated polymers; Contact; Copolymers; Energy; Energy conversion efficiency; Esters; Exact sciences and technology; Heterojunctions; Horner–Wadsworth–Emmons reaction; Natural energy; Organic polymers; Photovoltaic cells; Photovoltaic conversion; Physicochemistry of polymers; Polarity; Polymer solar cells; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Stacking; Stille coupling polymerization; Thiadiazolo[3,4-c]pyridine; Stille coupling polymerization; Conjugated polymers; Thiadiazolo[3,4-c]pyridine; Horner–Wadsworth–Emmons reaction; Benzo[1,2-b:4,5-b′]dithiophene; Polymer solar cells; Stille coupling; Short circuit currents; Solution polycondensation; Charge carrier mobility; Organic solar cells; Experimental study; Fill factor; Thermal stability; Open circuit voltage; Benzo[1,2-b:4,5-b']dithiophene; Electrochemical properties; Conjugated copolymer; Horner-Wadsworth-Emmons reaction; Optical properties; Preparation; Aromatic copolymer; Pyridine derivative copolymer; Thiophene derivative copolymer; Optical absorption
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2013.06.008

Three conjugated copolymers containing thiadiazolo[3,4-c]pyridine as electron- withdrawing unit were synthesized. The introduction of thiadiazolo[3,4-c]pyridine led to enhanced π–π stacking of the polymer in film and an unexpected non-ohmic contact on the interface of the polymer and hole extraction layer. PBDTT-T-DTPyT exhibited a high hole mobility of 1.2×10−2cm2V−1S−1. •The polymers containing thiadiazolo[3,4-c]pyridine in side chain were synthesized.•Thiadiazolo[3,4-c]pyridine led to an non-ohmic contact on the interface.•PBDTT-T-DTPyT exhibited a high hole mobility of 1.2×10−2cm2V−1S−1. A series of main-chain and side-chain type D–A copolymers containing benzo[1,2-b:4,5-b′]dithiophene (BDT) and thienylbenzo[1,2-b:4,5-b′]dithiophene (BDTT) electron-donating units and an electron-withdrawing unit based on thiadiazolo[3,4-c]pyridine, PBDT-DTPyT, PBDT-T-DTPyT, and PBDTT-T-DTPyT were synthesized for polymer solar cells (PSCs). The copolymers exhibit good thermal stability, strong absorption in the visible region, and relatively lower HOMO energy levels from −5.22 to −5.38eV. The results indicate thiadiazolo[3,4-c]pyridine led to enhanced π–π stacking of the polymer film owing to its stronger polarity. PBDTT-T-DTPyT exhibited a high hole mobility of 1.2×10−2cm2V−1S−1. The interaction of the thiadiazolo[3,4-c]pyridine in the polymers and the hole extraction layer led to a non-ohmic contact at the interface. The conventional and inverted bulk heterojunction polymer solar cells based on PBDTT-T-DTPyT as the electron donor and (6,6)-phenyl-C61-butyric acid methyl ester (PC61BM) as the electron acceptor exhibited power conversion efficiencies of 1.68% and 2.08%, respectively.