Impact of heat treatment on structural and optical properties of 5,10,15,20-tetraphenyl-21H,23H-porphine vanadium (IV) oxide thin films

Thin films of 5,10,15,20-tetraphenyl-21H,23H-porphine vanadium (IV) oxide, VOTPP, were placed on glass with an overall thickness of 495 nm utilizing the thermal deposition process. The films underwent annealing at various temperatures (323, 373, 423, 473, 573 K) for 3 h. The thermal behaviour of VOTPP powder was tested by DTA. The crystalline molecular structure, and surface morphology of as-deposited and annealed films were examined utilizing XRD, SEM, and AFM. The crystallinity of VOTPP film was enhanced and the crystallite size grew by boosting the annealing temperature. The RMS roughness of annealed film at 573 K is 14.87 nm. Optical parameters of as-deposited and annealed VOTPP films were determined by spectrophotometric measurements in the spectrum of (200–2500 nm). The absorbance spectrum of VOTPP films is characterized by the Soret band, which exhibits Davydov splitting into two peaks, B_x and B_y in the annealed films at 473 and 573 K. Additionally, Q and N bands are observed. Annealing reduces both the linear and nonlinear refractive index, as well as the dispersion parameters. Calculations for molar refractivity and absorptivity, nonlinear parameters, and optical conductivity at different annealing temperatures have been done. Additionally, the energy loss functions at different annealing temperatures were obtained. The electronic transition is indirectly allowed. Optical energies such as \({E}_{g}^{onset}\), \({E}_{g}^{opt1}\), \({E}_{g}^{opt2}\), and \({E}_{U}\) were observed to reduce as the annealing temperature elevated. All the optical parameters were compared with other porphyrin derivatives. This study demonstrates that thermally annealing is an efficient method in enhancing the optical and synthetic characteristics of VOTPP films, which serve as a viable absorbing layer in renewable energy systems.