By using the first principle pseudo-potential plane-wave method, the photoelectric properties of CdS doped with rare earth (Sc, Y, La) are calculated and analyzed. The calculation results show that: after Sc, Y, La doped, the lattice constants increase, the cell volume also expands. When Sc, Y or La substitutes for Cd, the Fermi energy moves to conduction bands, the band gap widens, the conductivity type is changed into n-type. These indicate that Sc, Y, La is a n-type dopant. The atoms of Sc, Y, La generate a large number of additional carriers near the Fermi energy level in order to improve the electronic structure. Rare earth atoms and the neighboring S atoms form a stronger interreaction and hence a higher covalent banding after incorporation of rare earth. After rare earth doped, the static dielectric constant, absorption coefficient and reflectivity decrease significantly, indicating that the conductivity and transmission increase. These results indicate that rare earth can effectively modulate the photoelectric properties of CdS.
