New D-A-D-A-D push-pull organic semiconductors with different benzo[1,2-b:4, 5-b '] dithiophene cores for solution processed bulk heterojunction solar cells

Abstract

The synthesis and characterization of two D-A-D-A-D push-pull organic semiconductors based on either his- (2-ethylhexyloxy) benzo [1,2-b:4,5-b'] dithiophene or bis- (triisopropylsilylethynyl) benzodithiophene electron rich core are described. The optical and electrochemical properties of these compounds indicate that these materials can absorb sunlight over a wide spectral range from 350 to 700 nm and exhibit suitable energy levels for efficient exciton dissociation. These small molecules were used as donor coupled with phenyl-C-71-butyric acid methyl ester acceptor for the fabrication of solution processed small molecule bulk heterojunction solar cells. The rigid and -conjugation of the silylacetylene substituted analog pi-extended compared to the hexyloxy substituted analog facilitates intermolecular packing interactions of small pi-pi charge transfer and intermolecular molecule which induce a deep HOMO level, producing a high open circuit voltage of similar to 0.98 V. The achieved PCE was 5.69% when the active layer hexyloxy analog: phenyl-C-71-butyric acid methyl ester was processed with optimized 1-chloronaphathalene additive. (C) 2015 Elsevier Ltd. All rights reserved.