Low band gap disk-shaped donors for solution-processed organic solar cells

Abstract

Disk-shaped donors 1–4 composed of a pyrene core, dithiophene linkers and rhodanine terminates were synthesized and their optical and electrochemical properties were investigated. The introduction of rhodanine terminal units into the pyrene-cored donors could effectively broaden the absorption spectrum and improve the molar absorption coefficient. The positions of thiophene oligomer in the pyrene core affected their optical and electrochemical properties as well as the molecular ordering and carrier transport properties in the solid state. The energy levels of these molecules are suitable for donor components in bulk heterojunction solar cells with fullerene derivatives. A 4/PC₇₁BM cell achieved an overall power conversion efficiency of 3.7% with a short-current density of 8.4 mA cm⁻², open-circuit voltage of 1.09 V, and fill factor of 41% under one sun condition.