Optical characterization of chloroaluminium phthalocyanine (ClAlPc) thin films

Thin films of ClAlPc of 100-300 nm thickness were sublimed onto glass substrates in high vacuum. Studies of the molecular structure of ClAlPc have been made using films deposited at various temperatures and films annealed after deposition at room temperature. The optical properties in both monoclinic and triclinic forms are reported. Optical data have been obtained from both absorption and reflectivity spectra over the wavelength range 350-800 nm. Monoclinic films show two absorption bands, an exciton absorption on the low-energy side of the transparent band and a fundamental absorption above 2.55 eV. A direct allowed transition at 3.05 eV was observed. A doublet of energies in the absorption spectra of the monoclinic form at 1.74 and 1.9 eV was also observed in good agreement with previous findings for other metal phthalocyanines, including CuPd, PbPc, NiPc and CoPc.