Paper Title
Density Functional Theory Investigations on the Electronic and Optical Properties of Vinyl Based Systems

Organic solar cells essentially needed lower band gap conjugated polymers for massive sunlight cultivation. Tuning electron rich and electron deficient units in a conjugated polymer can ease to reduce the band gap with high power conversion efficiency can be reached with this altered D-A units. Accordingly, we constructed seven methodically tuned conjugated polymers I-VII, where a vinyl-pyridine electron moiety is linked with each of seven fused ring electron rich moieties (auxochrome altered di-thiophene Dione). The calculation shows that the monomer moieties I and II, have lower band gaps and wide range of absorption solar light among the seven systems. An electron donating group of amine and withdrawing group of carbonyl is not only allows to lower the LUMO and increase the HOMO energy levels, but also altered the solar light absorption range. From the compared results of monomer I and VII given an idea to understand the role of hetero atoms on the conjugated donor-acceptor units to be lowered the band gap as also increase the range of the visible light absorption. This study revealed introduces and choose the position of the hetero atoms affect the optoelectronic properties of the copolymers. This remarkable study furnishes an idea to synthesis of appropriate co-polymers to well optoelectronic devices. Keywords— TD-time dependent, DFT-density functional theory, Organic photovoltaic cell, pyridine, band gap, dihedral angle.