Photoelectrical properties of doped cadmium sulphide powders

Photosensitive powders of CdS were prepared with different concentrations of dopants. Doses of donors (Cl−) and acceptors (Cu2+, Ag+) varied from 0 to 41 and from 0 to 9 mg/g CdS, respectively. Reflectance, absorption coefficient and resistance dependence on illumination intensity and voltage at the wavelength of about λ = 630 nm and photovoltage spectra in the range 450–900 nm were measured on layers prepared from the powders. The value of absorption coefficient grew with the increasing dopant concentrations; acceptors appeared more efficient than donors. Reflectance decreased with growing acceptor dose. Using the values of reflectance, absorption coefficient and resistance the corrected photovoltage, as the measure of the concentration photogenerated charge carriers, was calculated. The ratio ( σ IGB ) of the corrected photovoltage and photocurrent was used as the criterion of intergrain barrier conductivity. All doped samples exhibited similar value of σ IGB which was about three orders of magnitude lower than that of undoped sample.