Effect of fused triphenylamine core in star-shaped donor-π-acceptor molecules on their physicochemical properties and performance in bulk heterojunction organic solar cells

Abstract

In this work, the synthesis of a novel star-shaped donor-acceptor molecule I with acridine-based core being a fused derivative of triphenylamine and linked through π-conjugated terthiophene spacers and terminal hexyldicyanovinyl electron-withdrawing units is reported. Its physicochemical and photovoltaic properties were comprehensively studied and compared to those of molecule II being a structural analog but with a pristine propeller-like triphenylamine core. The novel molecule shows combination of the higher crystallinity, solubility and thermal stability. As compared to II, bulk heterojunction organic solar cells based on I as a donor and PC71BM as an acceptor showed the three times higher hole mobility, 50% larger external quantum efficiency, which resulted in up to twice higher power conversion efficiency reaching 6.14%. This work demonstrates that the triphenylamine core fused by p-tolylmethylene groups in the star-shaped donor acceptor molecules is a promising building block to design highly soluble and crystalline materials for organic optoelectronic devices.