Tuning the optoelectronic properties of indacenodithiophene based derivatives for efficient photovoltaic applications: A DFT approach

In this study, five novel push-pull acceptor molecules with A-B-D-B-A arrangement have been formulated in the quest to boost the organic solar cells (OSCs), with respect to their electrical, optical, and chemical characteristics. Substitution of end-capped acceptor moieties in non-fullerene materials is an effective approach of molecular modeling, which finely tunes the optoelectronic attributes of OSCs. The recently altered molecules (Y1-Y5) were flanked with different electron withdrawing units carrying indacenodithiophene (IDT) as the central electron donating core. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analysis were executed at B3LYP functional with 6-31G (d,p) basis set to investigate the geometrical as well as optical parameters such as quantum mechanical descriptors, light harvesting efficiency, ionization potential energy, absorption properties, electron affinity, dipole moment, molecular electrostatic potential, transition density matrix, the density of states, and reorganization energies. All of these studied molecules revealed greater electronic transitions, superior optical properties, fast charge mobilities, and better solubility in the polar solvent when compared to the reference molecule. Amongst all these derived molecules, Y1 emerged as a distinctive candidate, exhibiting the highest maximum absorption wavelength (884 nm) in chloroform along with the smallest energy gap (1.72 eV) as well as the lowest optical gap (1.40 eV). Moreover, it has the highest electron affinity and ionization potential energy, least interaction coefficient, exciton binding energy, and reorganization energy (λe = 0.00340 eV), which can be ascribed to its potent electron withdrawing moieties, which intensifies the transfer of charge between the donor and acceptor units within a molecule. We expect these modifications in the terminal groups around the central core to provide strong theoretical strategies to construct and amplify the photovoltaic parameters of OSCs in the future.