Stationary and modulated absorption spectroscopy of copper phthalocyanine (CuPc) layers grown on transparent substrate

Abstract

Copper phthalocyanine thin films grown on glass and quartz substrates by the thermal evaporation method were investigated using stationary and modulated photoabsorption as well as photoreflectance spectroscopy. The stationary and modulated studies at room temperature were performed in the wavelength range 200–1200 nm and 400–1200 nm, respectively. The absorption coefficient of investigated layers was determined directly from the transmission spectrum and fitted in terms of the mixed Lorentz–Lorenz model, which assumed five oscillator components. Sensitive modulated spectroscopy, which enabled us to emphasize weakly visible transitions in the Q-band spectral region, was also performed to estimate the electronic structure of metallophthalocyanine layers. The complex nature of excited states of the metallophthalocyanine layers gave us abundant modulated spectra. These spectra were fitted using the third derivative line shape given by the Aspnes formula. Modulated photoabsorption and photoreflectance spectra for CuPc thin layers are presented for the first time in this paper.