Morphological study of polymer/fullerene interfaces via benzene-PC70BM interaction

Abstract

We designed and synthesized a series of highly soluble random copolymers (P(BDTT-PhC8TPD-TPD)) comprising a two-dimensional (2D) electron-rich 2-ethylhexylthiophene-substituted benzo[1,2-b: 4,5-b'] dithiophene (M1) electron-rich unit and various ratios of two side chain-functionalized thieno[3,4-c]-pyrrole-4,6-diones (M2 and M3) as planar electron-deficient units. The morphologies and photovoltaic performances of the bulk heterojunction blend films were examined, revealing concentration-dependent competitive benzene-benzene and benzene-fullerene interactions. A bulk heterojunction solar cell prepared using 10 mol% M2 (RP1) and PC70BM exhibited a power conversion efficiency (PCE) of 4.9%, representing a significant improvement over the PCE (1.1%) obtained from parent copolymer (P1). The PCE in these cells was strongly associated with the nanoscale morphology of the BHJ film, which depended on the higher miscibility of RP1 with PC70BM compared to RP2 (M2: 20 mol%), and RP3 (M2: 30 mol%). (C) 2015 Elsevier B.V. All rights reserved.