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

Benzimidazole based metal free organic dyes (D-pi-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-n-bridge-acceptor dyes, N,N-diethylaniline and triphenylamine were act as donors and benzimidazole derivatives were act as pi-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 (DFF) 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 AM 1.5 illumination (85 mW/cm(2)). (C) 2014 Elsevier Ltd. All rights reserved.