DFT and TD-DFT studies of the π-bridge influence on the photovoltaic properties of dyes based on thieno[2,3-b]indole

In this paper, a theoretical study has been conducted using the density functional theory (dft) and time-dependent density functional theory (td-dft) methods on a series of ten organic donor-π-acceptor dyes, their π-conjugated bridge is based on the thiophene and benzene, the thieno[2,3-b]indole was used as an electron donor and the acid 2-cyanoacrylic was used as an electron acceptor group. the properties of all dyes, including frontier molecular orbitals (homo and lumo), gap energy (e_homo- e_lumo), intramolecular charge transfer, absorption and emission spectra and open- circuit voltage (vₒc) are investigated theoretically to confirm which dyes can produce great performance for dye-sensitized solar cell.the results of these investigations indicate how the electronic, optical and photovoltaic properties can greatly improve by increasing of the number of the thiophene and benzene on the bridge of dyes, leading us to suggest them as a good candidates for dye-sensitized solar cell.