Tuning the optoelectronic properties of oligothienyl silane derivatives and their photovoltaic properties.

Four new Donor-Acceptor (D-A) type oligothiophenes based structures (C1-C4) were designed by substituting different acceptors moieties around tetrahedral silicon core to simulate their photovoltaic properties. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) quantum analysis were carried out to reconnoiter various parameters of solar cells. A comparative analysis has conducted between designed structures and reference molecule R to conclude our simulated results. Among all the structures, C2 has displayed highest absorption values (380 nm) with red shift and minimum band gap (Δ) of 4.11 eV in dichloromethane at DFT-CAM-B3LYP/6-31G (d,p) using IEFPCM model. The C2 has also shown the lowest values of electron reorganization energy (λe = 0.018eV) and hole reorganization energy (λh = 0.015eV) therefore, could be suggested for use in organic solar cells because of its most noteworthy charge carrier mobilities. Again, C2 has the different trend in TDM graph because the electron density is present in the lower right part of core unit and in the acceptor moiety due to high electron affinities of end capped acceptor having cyanide groups.