Cyanovinyl substituted benzimidazole based (D–π–A) organic dyes for fabrication of dye sensitized solar cells

•Benzimidazole based donor-π-acceptor dyes were synthesized through one step process.•The synthesized dyes were used as sensitizers for dye-sensitized solar cells.•Cyanovinyl unit containing dyes show more than two times higher efficiency.

Benzimidazole based metal free organic dyes (D–π–A) with and without cyanovinyl unit have been designed and synthesized via one step processes and tested as sensitizers in the dye sensitized solar cells (DSSC). In such donor-π-bridge-acceptor dyes, N,N-diethylaniline and triphenylamine were act as donors and benzimidazole derivatives were act as π-bridge as well as acceptor. The relationship between molecular structure and optoelectronic properties of the synthesized dyes as well as their DSSC performances were studied by UV–vis and fluorescence spectroscopy, cyclic voltammetry (CV) and Density Functional Theory (DFT) calculation. Introduction of cyanovinyl unit in between the donor and benzimidazole leads to the significant improvement in the optoelectronic properties and DSSC performance. In general, the cyanovinyl unit containing dyes based DSSCs show more than two times higher efficiency than the dyes without cyanovinyl unit based DSSCs. Among the fabricated DSSC, the dye contain triphenylamine donor and benzimidazole with cyanovinyl unit based DSSC shows maximum power conversion efficiency of 3.47% under AM1.5 illumination (85 mW/cm2).

Graphical abstractBenzimidazole based metal free organic dyes (D–π–A) with and without cyanovinyl unit have been designed and synthesized via one step processes and tested as sensitizers in the fabrication of dye-sensitized solar cells (DSSC). Among the fabricated DSSC, the dye contain triphenylamine donor and benzimidazole with cyanovinyl unit based DSSC shows maximum power conversion efficiency of 3.47% under AM1.5 illumination (85 mW/cm2).Figure optionsDownload full-size imageDownload as PowerPoint slide