Strategies toward the end-group modifications of indacenodithiophene based non-fullerene small molecule acceptor to improve the efficiency of organic solar cells; a DFT study

The non-fullerene acceptor molecules AT1, AT2, AT3, AT4 and AT5 that are developed by making alteration at central position of reference molecule ATR demonstrate significant absorption in visible regions. Open circuit voltage of ATR and AT1-AT5 acceptor molecules was calculated by making their complex with PTB7-Th donor. [Display omitted] •Five small molecules have been designed by changing terminal acceptors of ATR molecule.•Almoat all newly designed acceptor molecules have lower band-gap and highest λmax as compared to reference molecule ATR.•Reorganization energy of designed molecules are smaller than ATR which exposed their greater charge mobilities.•Different photovoltaic properties of all molecules are estimated to evaluate the efficiency of OSCs. In this study, five indacenodithiophene (IDT) core-based small acceptor molecules (AT1-AT5) were designed by replacing the terminal acceptor groups of reference molecule (ATR) with five different electron-withdrawing groups. The density functional theory (DFT) was employed to investigate the photovoltaic properties of the newly developed molecules. The MPW1PW91/6-31G (d,p) methods have been used to investigate the effects of different terminal acceptor moieties on the FMOs, density of states (DOS), maximum absorption, the reorganization energies, transition density matrix, dipole moment,and open-circuit voltage (VOC) and then all these properties of modified molecules are compared with reference molecule. The VOC of all studied molecules is computed with respect to donor PTB7-Th. Many of these properties have been improved considerably in modified molecules. Amongst, all the developed chromophores, the AT4 molecule revealed the highest λmax (802 nm), a reduced bang-gap of 2.01 eV, and smaller electron and hole reorganization energies (0.0056611 eV and 0.0063966 eV, respectively), lowest first excitation energy (1.54 eV), and greatest electron affinity (3.44 eV). While AT3 has the least exciton binding energy (0.46 eV) and significant dipole moment (0.69 D) than all other tailored structures. Thus, these results demonstrate that the novel molecules are convincing factors in constructing the extremely effective NFAs photovoltaic cells.