Designing Novel Photosensitizers Based on Pyridoquinazolinone and Its TiO₂-Adsorbed Complexes with Efficient Photovoltaic Performance in DSSCs: A DFT Insight

Developing photosensitizers for dye-sensitized solar cells (DSSCs) is a hot topic in energy conversion and optoelectronic research. To address the rapidly increasing demand for DSSCs, we attempted to construct a series of D–π–A-based (F1–F9) innovative photosensitizers with resonant optoelectronic properties employing bridging core modification. The geometrical, photovoltaic, photophysical, thermodynamic, and electronic properties of the newly developed dyes were explored, and the potential impact of π-linkers (P1–P10) on the DSSC efficiency of the pyridoquinazolinone-based sensitizer was determined. Frontier molecular orbital (FMO), natural bond orbital (NBO), transition density matrix (TDM), electron density difference map (EDDM), molecular electrostatic potential (MEP), and density of states (DOS) analysis was performed, and the excited-state lifetime ( \(\tau )\) $\tau )$ , open-circuit voltage (V_OC), electron regeneration energy (ΔG^reg), electron injection driving force (ΔG^inject), electronic coupling constants (V_RP), and intramolecular charge transfer (ICT) parameters q^CT (e⁻), D^CT (Å), H index (Å), ∆ (Å), t index (Å), and μ^CT (D) for the proposed dyes were computed. The photoelectronic and chemical transfer parameters of the fabricated dyes (F1–F9) near the titania–electrolyte interface (dyes@TiO₂) proved the better accumulation and recombination of the dyes@TiO₂ model. The lowest unoccupied molecular orbital (LUMO) energies of all proposed dyes were found to be higher than the 4.0 eV of the TiO₂ conduction band, while the highest occupied molecular orbital (HOMO) energies were lower than the electrolytic redox potential energy of −4.80 eV. Therefore, the proposed dyes have an energy advantage for injecting excited electrons effectively, allowing oxidized dyes for efficient regeneration. When compared to standard R values of 5.24 eV, 399.79 nm, and 3.10 eV, the developed compounds (F1–F9) had a smaller energy gap (4.58–5.24 eV), a broader absorption wavelength (362.66–456.95 nm), and a lower transition energy (2.71–3.42 eV). Although all the designed dyes might be used as effective sensitizers for DSSCs, the P4 spacer in F3 is a promising candidate for use in high-performance DSSCs owing to promising photovoltaic properties, including the longer wavelength (456.95 nm), lower excitation energy (2.71 eV), highest light harvesting efficiency (LHE) (0.99), and V_RP (−1.25) with a lower band gap of 4.61 eV. Results proved that the pyridoquinazolinone dyes explored in this work have the potential to improve light-to-power conversion efficiency, J_SC, and V_OC in a DSSC system, and may result in materials with properties that are appropriate for use in DSSCs.