Effect of illumination on the structural and optical properties of Cu (II) tetraphenyl porphyrin (CuTPP) thin films

CuTPP thin films were prepared by thermal evaporation technique, on glass and quartz substrates. Illumination by a white light of incandescent lamp (150 W) was found to be accompanied by structural effects, which, in turn, lead to changes in the optical properties of CuTPP thin films. An optical characterization method based on spectrophotometeric measurements of transmittance and reflectance at normal incidence of light in the wavelength range 200-2500 nm was used to analyze the optical properties of CuTPP thin films. The obtained optical constants were used to estimate the type of optical transitions for the as-deposited and illuminated CuTPP thin films. The optical parameters such as oscillator energy, Eo, dispersion energy, Ed, lattice dielectric constant, εL, high frequency dielectric constant, ε∞, and the ratio of the free charge carrier concentration to the effective mass, N/m⁎ were estimated.