Fused heterocyclic core-based molecules have high-performing advantages; however, non-fused heterocyclic materials deserve to be studied because of their facile synthetic routes and tunability in optoelectronic properties. In this work, we reported five molecules, namely, D1, D2, D3, D4, and D5 containing imidazolyl–thienyl–imidazolyl-based core, and four peripheral TPA donor units substituted with five acceptors A1, A2, A3, A4, and A5 by thiophene spacer were simulated for theoretical investigation of photovoltaic properties using reference R molecule as a model. For the optimization of geometry and forecasting important electronic parameters, computations with density functional theory-based B3LYP functional and 6-31G (d, p) basis set in both gas and THF were carried out. The calculations include frontier molecular orbital (FMO) energies, band gap energies, density of state (DOS), transition density matrix (TDM), reorganizational energies of hole and electron, molecular electrostatic potential (MEP), open-circuit voltage (Voc), and power conversion efficiencies (PCE). The results show that this molecular engineering of non-fused rings endows these molecules with interesting features, including the shift in absorption, change in frontier orbital energies, and decrease in reorganizational energies and elevating device efficiencies PCE = 7.44% when compared with reference R = 1.35%. The molecular strategy of these new molecules give us the possibility that these simple structured, and easy to chemically modified non-fused rings can be used as building blocks in OSCs and PSCs. Graphical abstract: (Figure presented.). © The Author(s), under exclusive licence to the Institute of Chemistry, Slovak Academy of Sciences 2024.