Small molecular push–pull donors for organic photovoltaics: effect of the heterocyclic π-spacer

Abstract

A series of (D–π–A) small push–pull molecules involving a triphenylamine electron-rich group (D) connected to a dicyanovinyl electron-deficient unit (A) through different chalcogenophene type π-connectors has been synthesized. Optical and electrochemical results reveal that the replacement of furan by thiophene and selenophene leads to a progressive decrease of the optical band gap of the material and to a parallel increase of hole mobility and power conversion efficiency (PCE). Thus, a PCE of 3.33% has been obtained for a simple air-processed solar cell involving the selenophene-based donor and the [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) as the acceptor.