Synthesis of dipyrrolopyrazine-based sensitizers with a new pi-bridge end-capped donor-acceptor framework for DSSCs: a combined experimental and theoretical investigation

Abstract

The strategy of developing organic dyes with exceptional optical, thermal, and stable photovoltaic properties has attracted substantial attention in the replacement of high-cost traditional dyes in DSSCs. Herein, we synthesized four dyes with a D-pi-A configuration in order to study the variation produced in the optical, thermal, redox and photovoltaic properties by substitution of different donors and acceptors in the dipyrrolopyrazine (DPP) system. These push-pull systems are based on a pyrrolopyrazine spacer, end-capped with donors (N,N-dimethylamine, and thiophene) and acceptors (pyridine, -COOH, and -CN). The multidisciplinary study concerning the optical, thermal, redox, and photovoltaic characterization of the dyes reveals that compound 3a exhibits the best overall conversion efficiency as a sensitizer in TiO2 dye sensitized solar cells. The theoretical calculations together with experimental data allow us to quantify the charge transfer character of dyes.