Electron Withdrawing Substituent that Control Band Gap and Planar Conformation in Push-Pull Molecules Through Non-Covalent Interactions: Density Functional Theory Study
Benzo[1,2-b:6,5-b’]dithiophene-4,5-dione (BDTD) is used as an intermediate to synthesise acceptor unit for organic solar cell. But it has dual activity of both donor and acceptor is not yet tested. In this study, BDTD, DTBT and DTBTD considered as donor and determined its optoelectronic properties along with benzothiadiazole moiety. The band gap, HOMO, LUMO and absorption wavelengths are scrutinised and studied how the optoelectronic property affected when introducing electron-withdrawing substitutions such as F, CN and NO2 onto the benzothiadiazole unit. The electron-hole distance and real electron donor and acceptor system identified during the electronic transition from the computed density for the ground and excited states. Strong hydrogen bond interaction and strong steric repulsion between donor and acceptor units observed while introducing different electron withdrawing substituents onto the benzothiadiazole acceptor unit. Fragment contribution on the molecular orbital energy levels support the results that the donor character of DTBT, DTBTD and Dual character of BDTD. Newly designed molecule reached the power conversion efficiency Ì´ 8% predicted by the scharber diagram.
Saravanan C , Nasrin IS and Milind SD*