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Synthesis of D-π-A-π type benzodithiophene-quinoxaline copolymers by direct arylation and their application in organic solar cells

: Zimmermann, Diana; Sprau, Christian; Schröder, Jonas; Gregoriou, Vasilis G.; Avgeropoulos, Apostolos; Chochos, Christos L.; Colsmann, Alexander; Janietz, Silvia; Krüger, Hartmut


Journal of polymer science. A, polymer chemistry 56 (2018), No.13, pp.1457-1467
ISSN: 0360-6376
ISSN: 0887-624X
ISSN: 1099-0518
ISSN: 1096-990X
European Commission EC
FP7-NMP; 604603; MatHero
New materials for highly efficient and reliable organic solar cells
Journal Article
Fraunhofer IAP ()

Conjugated copolymers based on benzodithiophene (BDT) derivatives and thiophene‐quinoxaline‐thiophene (TQT) segments represent an efficient class of light harvesting materials for organic photovoltaic (OPV) applications. Commonly, BDT‐TQT copolymers are synthesized by Stille cross‐coupling polymerization. In this study, alkoxy and thienyl functionalized alternating BDT‐alt‐TQT copolymers are synthesized by direct arylation polymerization (DArP), using Ozawa conditions. An extensive optimization of the reaction conditions such as the catalytic system, solvent, temperature, base, and the concentration of the catalyst is accomplished. The optical and electrochemical properties of the copolymers obtained by DArP are compared to the reference polymers synthesized by Stille cross‐coupling polymerization. Finally, the optimized BDT‐alt‐TQT copolymers are incorporated into organic solar cells as electron donors. The solar cells of the DArP copolymers exhibit power conversion efficiencies up to 80% (rel.) of their Stille cross coupling analogues.