Designing of small organic non-fullerene (NFAs) acceptor molecules with an A−D−A framework for high-performance organic solar cells: A DFT and TD-DFT method

The main objective of this research was to design non-fullerene acceptors (NFAs) A–D–A framework, using carbazole and benzothiazole derivatives. Density functional theory (DFT) was used to calculate the geometry optimized structures and electronic properties at B3LYP functional with a 6-311G basis set in the gas and solvent phase. The frontier molecular orbitals (FMO), bandgap, open-circuit voltage (VOC) and dipole moments of these developed acceptors have been calculated. The theoretical UV absorption spectra were calculated from time-dependent DFT with the same level of theory used DFT method. They show a suitable bandgap (2.24–2.93 eV) and dipole moment (1.8–10.8 Debye). The maximum wavelength (λmax) for all studied molecules in the range is 665.17–679.97 in both gas and solvent. A slight redshift was observed in all acceptors selected for chlorobenzene compared with gas phase absorption. The NFA A11 has the lowest bandgap energy (2.24 eV), gas-phase excitation energy (1.86 eV) and chlorobenzene excitation energy (1.86 eV). As a result, A11 is predicted to be a good contender for organic NFAs in the future. The open-circuit voltage (VOC) values range from 1.53 to 2.56 eV. Consequently, the optoelectronic, molecular orbital distribution and A11 and A12 molecules were suitable acceptors for NFAs.