Nanostructured Pyrano[3,2‐ <i>c</i> ]Quinoline–Antipyrine Thin Films: Synthesis, Optical Characterization, and Applications in Photovoltaic and Photodiode Devices

The condensation of 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐ c ] quinoline‐3‐carboxaldehyde with 4‐aminoantipyrine affords pyrazolylamino‐methylidenepyrano[3,2‐ c ]quinoline ( PAMPQ ). The compound is characterized using elemental analysis, IR, 1 H NMR, 13 C NMR, and mass spectrometry. Density functional theory calculations at the B3LYP/6‐311++G(d,p) level are employed to explore the optimized structure, vibrational spectra, molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs), and nonlinear optical properties. Drug‐likeness is also assessed to evaluate its pharmaceutical potential. X‐ray diffraction (XRD) analysis confirms the crystalline nature of the compound, determining its preferred orientations and Miller indices. Williamson–Hall analysis reveals an average crystallite size of 14.5 nm and a lattice strain of 3.7 × 10 −4 . Optical absorption studies on PAMPQ thin films exhibit absorption peaks at 2.8, 3.41, and 4.21 eV, corresponding to direct bandgaps of 3.00 and 3.57 eV. A single‐oscillator model yields an oscillator energy of 3.88 eV, dispersion energy of 17.44 eV, and high‐frequency dielectric constant of 4.55. When coupled with n‐Si, PAMPQ thin films show enhanced photovoltaic performance, with improved rectification and measurable open‐circuit voltage ( V oc ) and short‐circuit current ( I sc ) under varying illumination. These results highlight the promising potential of PAMPQ thin films for applications in optoelectronic and photovoltaic devices.