A new two-dimensional donor/acceptor copolymer based on 4,8-bis(2′-ethylhexylthiophene)thieno[2,3-f]benzofuran for high-performance polymer solar cells

Abstract

A new alkylthienyl substituted thieno[2,3-f]benzofuran (TBF)-based polymer (PTBFTDTBT) was synthesized and characterized. PTBFTDTBT had a high molecular weight, good solubility in common organic solvents, broad visible absorption from 300 to 750 nm, and a relatively deep highest occupied molecular orbital level (−5.2 eV). PTBFTDTBT also showed a field hole mobility up to the order of 10⁻² using an organic field effect transistor (OFET) method and an order of 10⁻² using a space-charge-limited current (SCLC) method. With the structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/PTBFTDTBT:PC₇₁BM (1 : 2, w/w)/Ca/Al, a power conversion efficiency of 6.42% was obtained with a high short circuit current (J_sc) of 13.51 mA cm⁻² and fill factor (FF) of 61%, under the illumination of AM1.5G, at 100 mW cm⁻², without any post-treatment. The study demonstrates that TBF is a promising building block for organic electronics.