Structural and optical properties of spin coated ZnTTBPc thin films for optoelectronics via DFT and experiments

The present research provides a comprehensive theoretical and experimental investigation into the structural and optical properties of zinc 2, 9, 16, 23-tetra-tert-butyl-29 H,31 H-phthalocyanine (ZnTTBPc). Density functional theory (DFT) calculations at the B3LYP/6-31G (d, p) level, were utilized to optimize the molecular structure, analyze Mulliken charges, generate a molecular electrostatic potential map, and compute frontier molecular orbital energies of ZnTTBPc molecule. The nonlinear optical properties, including polarizability and hyperpolarizability, were also determined, confirming the molecule's applicability for nonlinear optical applications. Experimentally, spin-coated ZnTTBPc thin films were fabricated on quartz substrates. Structural characterization using X-ray diffraction and Raman spectroscopy indicated the amorphous nature of the thin films, whereas field emission scanning electron microscopy demonstrated a uniform, nanostructured morphology. Optical properties, including absorption coefficient, refractive index, and extinction coefficient, were analyzed over a wide spectral range (200-2000 nm), demonstrating the presence of direct optical transitions. The energy band gaps corresponding to the Q and B bands were obtained from Tauc plot analysis, with values of 1.42 and 2.25 eV respectively. The dispersion parameters and dielectric properties were evaluated using a single oscillator model. The nonlinear optical parameters such as the third-order nonlinear susceptibility, nonlinear refractive index and nonlinear absorption coefficient were calculated using semi-empirical relations. The results demonstrate that ZnTTBPc thin films possess excellent optical and nonlinear properties, making them highly promising candidates for advanced optoelectronic and photonic devices. This integrated theoretical and experimental approach underscores the importance of molecular design and fabrication techniques in optimizing materials for cutting-edge applications.