Structural Properties and Uv to Nir Absorption Spectra of Metal-free Phthalocyanine (h2pc) Thin Films

The structural properties and absorption spectra of H2Pc thin films have been studied. The films used in these studies were thermally evaporated on glass/quartz substrates with thickness ranging from 60 to 460 nm. The XRD studies of H2Pc thin films showed that the as-deposited films have α-form with monoclinic system. The mean crystallite size (L), the dislocation density (δ) and the strain (ξ) were evaluated. The molecular structure of H2Pc thin films is confirmed by analysis of (FTIR) spectra. The surface morphology of H2Pc thin films was examined by scanning electron microscope. The absorption spectra of H2Pc recorded in the UV – VIS – IR region for the as-deposited and the annealed thin films of different thickness have been analyzed. The spectra showed two absorption bands namely the Q-band and the Soret (B)-band. The Q-band shows its characteristic splitting (Davydove splitting) with ∆Q = 0.21 eV. Values of some important optical parameters, namely optical absorption coefficient (α), molar extinction coefficient (εmolar), half-band-width (∆λ), electronic dipole strength (q) and oscillator strength (f) were calculated. The fundamental and the onset of the indirect energy gaps were also determined as 2.47 and 1.4 eV, respectively.