Computational modeling of oligothiophenes-based donor molecules to boost optoelectronic attributes of organic solar cells

The computational modeling of seven oligothiophene-based donor molecules (TZ1–TZ7) designed by acceptor modification at the terminal position of the literature molecule (TZR) were discussed for organic solar cells (OSCs). DFT simulations using B3LYP/def2svp levels were performed to study the optoelectronic, and PV properties of TZ1–TZ7. A range of essential aspects for efficient small donor molecules like open circuit voltages (V_OC), excitation energy (E_x), dipole moment (μ), density of state (DOS), absorption maxima (λ_max), transition density matrix (TDM), binding energy (E_b), and frontier molecular orbitals (FMOs) of TZ1–TZ7 and TZR have also been investigated. DOS and FMOs analysis revealed a reduced energy gap (E_g) and effective charge transfer (CT) in the TZ1–TZ7 molecules. The absorption spectra were examined using TD-DFT. Due to smaller E_g, E_b, E_x, and higher λ_max, μ, the TZ1–TZ7 molecules exhibit remarkable optoelectronic properties. The computed V_OC (0.969–1.189) and fill factor (0.886–0.897) for TZ1–TZ7 lead to improved power conversion efficiency (PCE) ranging from 14.05% to 17.60%. All compounds are strongly recommended for fabricating efficient OSCs with excellent PV properties. The current work is a step towards environmentally friendly organic PV and will pave the way for future structural engineering research for the efficient material design of OSCs.