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2,1,3-Benzooxadiazole, thiophene and benzodithiophene based random copolymers for organic photovoltaics: Thiophene versus thieno[3,2-b]thiophene as pi-conjugated linkers

Göker, Seza
Hizalan, Gonul
Aktas, Ece
Kutkan, Seda
Çırpan, Ali
Toppare, Levent Kamil
Three conjugated random copolymers comprising benzodithiophene and thiophene as the donor units and benzooxadiazole as the acceptor unit, spaced with thiophene and thieno[3,2-b]thiophene π-bridges, were designed and synthesized. The effects of different linkers on the optical and electrochemical properties were investigated. The polymer containing a thieno[3,2-b]thiophene π-bridge revealed a red shifted absorption compared to its thiophene analogue. Morphological and photovoltaic properties of a polymer:fullerene blend film were investigated. The blend of one of the random copolymers (P2) and PC71BM ([6,6]-phenyl-C71-butyric acid methyl ester) revealed a photovoltaic performance efficiency of 5.17% due to the high short-circuit current density and fill factor.