Effect of thickness on structural and optical characteristics of Indium Phthalocyanine Chloride thin films for photodiode devices

Indium phthalocyanine chloride, InPcCl, in the form of thin films were prepared with different thicknesses by thermal evaporation technique. X-ray diffraction showed a hump at 2θ = 28°, which identified that the prepared InPcCl films have an amorphous structure. The particle size increased from 56 to 357 nm with increased film thickness as indexed by Atomic Force Microscope technique. The transmittance and reflectance spectral distribution of InPcCl films was measured through a range of 250–2500 nm of wavelength. The optical transition is indirectly allowed with two optical energy gaps (E_g1 = 1.37 eV and E_g2 = 2.84 eV) for InPcCl thin films, which are smaller than other phthalocyanine films. The dispersion parameters were calculated for the different film thickness of InPcCl films from refractive index analysis in the region of normal dispersion. The linear, third-order, non-linear refractive index and non-linear susceptibility have also been measured. The optical limiting response was evaluated for the InPcCl films under the He–Ne laser and a green diode laser. The InPcCl film of thickness 95 nm exhibits the highest output power values and the normalized power. This advanced result will hopefully apply to the field of photodiode devices in an industrial approach.