Low bandgap polymers with benzo [1,2-b:4,5-b '] dithiophene and bisthiophene-dioxopyrrolothiophene units for photovoltaic applications

New donor/acceptor polymers PBDTTPT1 and PBDTTPT2 with alternating benzodithiophene (BDT) and bisthiophene-dioxopyrrolothiophene (TPT) units were synthesized by Stille coupling reaction. The polymers had optical bandgaps of 1.78 and 1.82 eV, and HOMO energy levels of -5.30 and -5.35 eV for PBDTTPT1 and PBDTTPT2, respectively. Polymeric solar cell devices based on these copolymers as donors and PC(71)BM as acceptor showed the highest open circuit voltage of 0.95 V and power conversion efficiency of 2.68% under the illumination of AM 1.5, 100 mW/cm(2). (C) 2010 Elsevier Ltd. All rights reserved