A DFT approach toward designing selenophene-based unfused small molecule acceptors by end-capped modification for improving the photovoltaic performance of organic solar cells

In this study, we have developed a series of eight non-fullerene acceptors, constituting A-D-A type small molecules named (SS1-SS8) to enlighten the open-circuit voltage (Voc) and the efficacy of pre-existed SR (reference) molecule. Density functional theory has been adopted to computationally assess the optoelectronic features of fabricated molecules with the B3LYP/6-31G (d, p) level of theory. Several factors like charge transfer, light absorption, binding energy, dipole moment, and reorganization energy are studied. The frontier orbitals analysis revealed that all the newly developed molecules have less bandgap (ranging from 1.97 to 2.22 eV) than SR (2.23 eV). Similarly, these newly engineered molecules also revealed better light absorption by screening remarkable redshift from 676.23 to 789.28 nm than SR (673.83 nm) in chloroform. These molecules have remarkably reduced excitation energy ranging from 1.71 to 1.83 eV than SR 1.84 eV. The exclusive CT analysis is carried out via J61:SS8 complex because of the higher Voc of SS8 (acceptor). Additionally, SS8 has shown the least energy loss, making it a strong contender to be used to develop improved OSCs. Because of the exceptionally improved characteristics, these newly engineered molecules (especially SS8) can be considered potential aspirants for fabricating proficient OSCs. Representation of designing of eight molecules. Results of different analyses were computed through DFT for the evaluation of different photovoltaic properties.image