Copolymers from naphtho[2,3-c]thiophene-4,9-dione derivatives and benzodithiophene: synthesis and photovoltaic applications

A series of donor-acceptor (D-A) copolymers from a benzodithiophene (BDT) donor unit and a naphtho[2,3-c]thiophene-4,9-dione (NTDO) acceptor unit with different side chains, PBDTNTDO-C1, PBDTNTDO-C2 and PBDTNTDO-C3, were synthesized by a standard Stille cross-coupling polymerization. The thermal, optical and electrochemical properties of the copolymers were well investigated. Preliminary investigations of the copolymers based on the device structure of ITO/PEDOT : PSS/polymer: PC71BM (1 : 2)/Ca/Al showed power conversion efficiencies (PCEs) of 1.96% for PBDTNTDO-C1, 1.01% for PBDTNTDO-C2 and 2.21% for PBDTNTDO-C3 under the illumination of AM1.5, 100 mW cm(-2).