Optical properties of thin films of zinc phthalocyanines determined by spectroscopic ellipsometry

The optical properties of thin films based on unsubstituted and tetrafluoro-substituted zinc phthalocyanines synthesized by physical vapor deposition are studied within the wavelength range of 250–1000 nm. Spectroscopic ellipsometry shows that films based on zinc phthalocyanines have uniform thicknesses and optical parameters, strongly absorb visible light, and have characteristic absorption peaks corresponding to electronic transitions in the system of conjugated double bonds of phthalocyanine rings. Introduction of fluorine substituents into peripheral positions of the zinc phthalocyanine molecule leads to an increase in light absorption and a shift of the main absorption maximum to longer wavelengths (bathochromic shift). The absorption spectra are described using the Lorentz–Drude dispersion model. It is shown that the films based on a mixture of phthalocyanines can be well described using the Bruggeman effective medium model.