DFT/TD-DFT- guided design of conjugated thiophene–oxadiazole donors for organic photovoltaics

초록

Eight novel thiophene- and oxadiazole-based conjugated molecules were computationally designed and evaluated for application in bulk heterojunction (BHJ) organic solar cells (OSCs). Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations at B3LYP-D3/6–31 G(d,p) for ground states and TD-CAM-B3LYP/6–31 G(d,p) for excitations were employed to systematically investigate frontier molecular orbital (FMO) configurations, optical absorption properties, electronic HOMO-LUMO energy gaps, open-circuit voltage (V<inf>OC</inf>), density of states (DOS), and transition density matrix (TDM). Molecules AB1–AB3 exhibited significantly enhanced optical absorption, extending to approximately 735 nm, and optimal electronic HOMO-LUMO energy gaps of 1.59–2.1 eV, positioning them as promising candidates for enhanced solar photon harvesting. Moreover, AB1–AB3 molecules showed ideal alignment of HOMO and elevated LUMO energy levels relative to fullerene C<inf>70</inf>, facilitating efficient exciton dissociation and interfacial charge transfer. Comprehensive calculations of photovoltaic parameters, particularly V<inf>OC</inf> and fill factor (FF), highlight the potential high power conversion efficiency (PCE) achievable with AB1–AB3 paired with C<inf>70</inf> complexes. TDM simulations revealed clear electron–hole localization patterns and detailed electronic excitation pathways, reinforcing the efficacy of the molecular design strategy. Additionally, molecular electrostatic potential (MEP) and DOS analyses confirmed that precise electronic tuning significantly enhances photovoltaic performance. This study thus provides a robust computational foundation for the synthesis and testing of AB1–AB3, paving the way for the development of high-performance BHJ OSCs. © 2025 The Authors.

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