Synergistic charge-transfer dynamics of novel pyridoquinazolindone-containing triphenylamine-based push–pull chromophores: from structural optimization to performance metrics in photovoltaic solar cells and static, dynamic, solvent-dependent nonlinear optical response applications†

Modern technological breakthroughs depend on nonlinear optical (NLO) and photovoltaic (PV) materials, essential for creating advanced photonic devices and efficient solar cells. Herein, the NLO, PV, electrical, and photophysical characteristics of proposed chromophores (WLK-1–WLK-6) designed from pyridoquinazolindone-containing triphenylamine have been systematically altered by the addition of different spacers categorized as K1, K2, K3, K4, K5, and K6 (named as i-series). This fine-tuning was accomplished using TD-DFT, DFT computations, and the Scharber model. The impact of spectrum of medium polarity, ranging from the least polar to the most polar, including water (ε = 78.36), methanol (ε = 32.61), DMSO (ε = 46.83), tetrahydrofuran (ε = 7.43), benzene (ε = 2.27) and chloroform (ε = 4.71), is explored in detail utilizing the IEFPCM model on NLO and PV properties. Moreover, the response of different analyses like DOS, NCI, NBO, FMO, dipole moments (µ), and hyperpolarizability (β) in both gas, polar and non-polar solvents was analyzed. Our structure–property relationship studies revealed that adding extra spacer groups, particularly those containing thiophene spacers, considerably impacted the lowering of the energy gap (3.853–4.190 eV). The simulated UV-Vis spectra illustrate significant π → π* transitions and lower n → π* transitions, primarily in the near-infrared (IR) range of 558.613 to 429.844 nm. Push–pull chromophores showed extraordinary frequency-dependent NLO properties, SHG β(−2ω, ω, ω), and EOPE β(−ω, ω, 0) effect computed at laser frequencies of 1064 and 532 nm. Among the proposed compounds, WLK-6 with the K6 spacer demonstrated a smaller energy gap (3.853 eV), resulting in a maximum optical absorption peak at λ_max = 558.613 nm and the maximum hyperpolarizability in benzene (9.00 × 10⁴ a.u.), methanol (1.22 × 10⁵ a.u.), THF (1.12 × 10⁵ a.u.), DMSO (1.23 × 10⁵ a.u.), and water (1.23 × 10⁵ a.u.). Our study found that WLK-6, WLK-5, and WLK-1 compounds also had good photovoltaic (PV) capabilities, reaching a power conversion efficiency (PCE) of around 5% and an injection efficiency (ΔG^inject) of 0.191. In addition to these analyses, we performed topologic studies, such as TDM, ELF, NCI, MEP, LOL, and electron–hole overlap plots to better understand both intra and intermolecular interactions. Based on these results, it is clear that modifying longer π-linker groups in A–D–π–A conjugated systems benefits the optoelectronic characteristics and NLO responses for organic PV devices.