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

Abstract

The main objective of this research was to design non-fullerene acceptors 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 orbital’s (FMO), bandgap, Open-circuit voltage (VOC) and dipole moments of these developed acceptors have been calculated. The theoretical UV absorption spectrawere calculated from Time-Dependent Density Functional Theory (TD-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 to gas phase absorption.The non-fullerene acceptor A11 has the lowest bandgap energy (2.24 eV), gas-phase excitation energy (1.86 eV), and chlorobenzene excitation energy (1.86 eV) (1.86 eV). As a result, A11 is predicted to be a good contender for organic non-fullerene acceptors 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 non-fullerene acceptors.