Optical, electrical and photoelectrical properties of nanocrystalline cadmium selenide films for photosensor applications

In this work, CdSe powder was synthesized by using an aqueous route in the presence of polyethylene glycol as a surfactant. The as-prepared powder was used to prepare different film thickness (101-179 nm) using thermal evaporation technique. The structural, optical, electrical and photoelectrical properties of the films have been reported. The structural properties of the films were studied by X-ray diffraction and high-resolution transmission electron microscope techniques. The films were found to have nanostructure nature in which the particle size increases with increasing film thickness. The optical properties of the films were investigated using transmittance and reflectance spectra in wavelength range 200-2500 nm. The optical band gap of the films was determined as a function of film thickness and showed high band gap compared to bulk material due to quantum size effect. The refractive index was also calculated and analyzed in which the dispersion parameters were determined. The electrical resistivity was found to decrease with increasing film thickness due to size effect. Under illumination, the resistance of the films was found to decrease in which the films are promising candidates for photosensor applications.