DFT and TD‐DFT Investigation of π‐Conjugated Organic Donors for Solar Cells: Electronic, Optical, and Photovoltaic Properties

ABSTRACT This computational study investigates π‐conjugated structures based on dibenzothiophene (DBT) for high‐performance organic photovoltaics (OPVs). Leveraging experimental evidence highlighting DBTs promising optoelectronic properties, we conduct a systematic computational evaluation of modified DBT architectures. Density functional theory (DFT) calculations using Gaussian 09 were employed to optimize molecular geometries in gas and liquid phases. To identify the most accurate method for modeling electronic properties, we compare functionals (B3LYP, CAM‐B3LYP, MPW1PW91, and wB97XD) with the 6‐31G(d,p) basis set. For solid‐state simulations, CRYSTAL software with B3LYP/6‐31G(d,p) ensured consistency between isolated‐molecule and crystalline‐environment predictions. Four derivatives (M1–M4) with distinct substituted cores were analyzed via DFT/B3LYP/6‐31G(d,p). This method was used to discuss characteristics, including gap energy, frontier molecular orbitals, reactivity indices, exciton binding energy, reorganization energies, electrostatic potential, density of states, and photovoltaic parameters such as open‐circuit voltage, short‐circuit current, and fill factor with PC 61 BM as acceptor. We also obtained UV/Visible absorption wavelengths ( λ max ), excitation energies, oscillator strengths, dipole moments, and light‐harvesting efficiencies in both chloroform and gaseous phases. Every computed characteristic points to the potential of our proposed molecules for solar applications.