Band width widening and red shift in metal-organic complex zinc phthalocyanine for use as a photosensitizer

Thin film layered structures of ZnPc were deposited using vacuum evaporation at different substrate temperatures ranging from 100 °C to 250 °C in steps of 50 °C and vacuum cooled to room temperature in a vacuum of 10 −6 Torr. ZnPc thin films (thickness-1000–3000 Å, rate of deposition∼50 Å/s) were deposited onto cleaned glass slides and ITO coated glass substrates. ZnPc films were studied using a uv–vis spectrophotometer to know the feasibility of ZnPc as a photothermal phthalocyanine photosensitizer. The effect of substrate temperature and the thickness on the optical absorption spectra of ZnPc active layer was studied in the wavelength range 400–900 nm. ZnPc thin films have a sharp peak at 617 nm and a shoulder peak at 692 nm for a room temperature deposited film. It was found that ZnPc films deposited at higher substrate temperatures of 200 °C to 250 °C had a widening with a flat band for the absorption spectra in the range 500–800 nm. X ray diffraction, scanning electron microscope studies and electrochemical voltammogram for the ZnPc thin films were discussed.