Vacuum-evaporated, CdCl2-doped cadmium sulfide films for solar cell applications

CdCl₂-doped CdS films have been prepared using a vacuum evaporation technique with a goal of providing a low resistivity, large grain size, window layer for CdTe-CdS solar cells. CdS films with 0.05, 0.1 and 0.2% CdCl₂ doping have been grown. The effects of doping on the optical transmission, XRD, resistivity, carrier concentration, Hall mobility and microstructure have been investigated. N-type CdS films with resistivities of 2 to 10 Ωcm and Hall mobilities from 1 to 5 cm²/V-sec have been grown using this technique. The XRD patterns show that <002> is the preferred orientation. SEM analyses reveal that the grains in the films are columnar and their size increases from 70 nm for undoped CdS films to 150 nm for 0.2% CdCl₂-doped films