Study of low band gap DSSCs based on bridging bithiophene and biphenyl: theoretical investigation

In this paper, theoretical study using density functional theory (DFT) method (B3LYP level with 6-31G(d,p)) of four novel low band gap acceptor-donor organic materials based on thiophene and phenyl and linked to cyanoacrylic acid as acceptor group are investigated. Different electron side groups were introduced to investigate their effects on the electronic structure; the HOMO, LUMO, gap energy, ionization potentials, electron affinities and open circuit voltage (V-oc) of these compounds have been calculated and reported in this paper. The electronic absorption and emission spectra of these dyes are studied by time-dependent density functional theory calculations. A systematic theoretical study of such compound has not been reported as we know. Thus, our aim is first, to explore their electronic and spectroscopic properties on the basis of the DFT quantum chemical calculations. We think that the presented study of structural, electronic and optical properties for these compounds could help in designing more efficient functional photovoltaic organic materials.