Small molecule carbazole-based diketopyrrolopyrroles with tetracyanobutadiene acceptor unit as a non-fullerene acceptor for bulk heterojunction organic solar cells

Abstract

Herein, we investigated the photovoltaic properties of carbazole-based diketopyrrolopyrroles with tetracyanobutadiene acceptor units as highly efficient non-fullerene acceptors together with a D-A conjugated polymer, P, as a donor for polymer solar cells. After optimization, i.e. donor to acceptor weight ratio and solvent vapour annealing, the polymer solar cells exhibited power conversion efficiencies of up to 4.86% and 7.19% for DPP7 and DPP8 as acceptors, respectively. These results indicate that slight changes in the chemical structure of the small acceptor molecule significantly increase the efficiency of the device. The design and synthesis of these non-fullerene acceptors with broader absorption spectra extended towards the near infrared region may be key for the further development of high-performance and cost-effective solution-processed organic solar cells. © The Royal Society of Chemistry.