The effect of Cd substitution in PbS thin film on the optical properties

Thin films of CdxPb1-x S were prepared by chemical spray pyrolysis with ( x=0.6 , 0.7 , 0.8 , 0.9 , 1 ) .The optical properties of prepared thin films were studied by UV-VIS spectrophotomer . From the measurement of absorption and transmission , the optical parameters and the optical energy gap (Eg) were calculated .The optical energy gap (Eg) was increased with increasing the value of Cd from 1.2 eV when x=0.6 to 2.4 eV when x=1 . The maximum value of refractive index (n) is equal to 2.5 and the maximum value of extinction coefficient is varied between 0.2 to 0.45 depending on the value of x . The film with x=0.7 was doped by Ag in the ratio 1% ,3% and 5% . The film after dopping have a direct energy gap also and the value of Eg were increased with increasing (Ag) ratio , these values increased from 1.2 eV for absent Ag to 1.74 eV for 5% Ag .