Role of Heteroatom‐Doped Donors and Internal Acceptors in Enhancing Photovoltaic Properties of 2,2′:5′,2″‐Terthiophene π‐Bridged Photosensitizers

This study investigated metal‐free organic dyes having D‐π‐A and D‐A′‐π‐A frameworks for organic solar cells (OSCs). The influence of modifying the donor and internal acceptor in reference molecules ( N , O , and S ) on the structural, electronic, photovoltaic, and optical characteristics was analyzed by employing density functional theory (DFT). The UV–visible spectrum of the designed dyes was also simulated by employing time‐dependent DFT (TD‐DFT). The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and their energy gap (E gap ) are advantageous to understand the electron injection, electron transfer, and regeneration of the dye. The evaluated results suggest that short‐circuit current density (J SC ), energy for dye regeneration (ΔG reg ), electron injection driving force (ΔG inj ), light harvesting efficiency (LHE), open circuit voltage (V OC ), density of state (DOS), and power conversion efficiency (η) are affected by the insertion of donors and internal acceptors. The dye N with Carbazole donor has an efficacy of 4.15% at J SC of 15 mA cm −2 . The outcomes indicate that heteroatom‐doped donors and inserting internal acceptors have an impact on absorption energies and improve the photovoltaic characteristics in the D‐π‐A arrangement, suggesting that these dyes are better sensitizers for the assembly of OSCs.