Effect of acceptor on the electronic and optical properties of designed D-A-D molecules for organic solar cells by DFT and TD-DFT method

Searching for new and efficient energy sources to satisfy global energy demand is one of the most inspiring and challenging areas in scientific study in order to replace fossil fuel which is regarded as unsustainable and harmful to the environment. Solar energy through different technologies including organic solar cells (OSCs) seems to be one of the favorable alternatives. However, the efficiency of this category of solar cells needs significant improvements to become one of the best candidates for use as the best alternative energy source in solar cell technology. In this study, four donor molecules (D-A-D) were successfully created using two strong different donor moieties linked together by four different acceptors to form four M1, M2, M3, and M4 molecules to be used in OSCs technology. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods coupled with B3LYP hybrid functional and 6-311G basis set was employed to assess the optoelectronic as well as photophysical properties of four D-A-D designed molecules. All the designed molecules display promising results to be satisfactorily used in organic solar cell applications. However, among the designed molecules, M2 performs better than others due to the lowest energy gap of 1.83 eV and 1.9 eV, open-circuit voltage (VOC) of 1.5151 and 1.4817 and large maximum absorption wavelength (λmax) of 784.96 nm and 821.18 nm in gas and solvent phases, respectively. As a result, the designed molecule is remarkable and highly recommended to researchers for the development of widely effective solar cell system for practical uses.