Since CdS material has a direct and wide band-gap, it is very potential for fabricating photovoltaic devices. Due to its
wide band-gap, CdS film can be acted as a window material to combine with Cu(In, Ga)Se<sub>2</sub> film. To obtain a quite
uniform, easily scaling-up, and inexpensive sample, the CdS thin film with a thickness of 50 nm was deposited by using
chemical bath deposition (CBD) technique. Through varying annealing temperatures and holding times, the electrical
and optical properties of CdS film could be obviously improved. By Hall measurements, the carrier concentration of CdS
sample S8 annealed at 100°C with 20 min is the maximum and its surface resistivity is the minimum. Summarizing these
measuring data, we find that the concentration and the mobility of sample S8 are 2.4×10<sup>21</sup> cm<sup>-3</sup> and 20.5 cm<sup>2</sup>/v-s,
respectively, and it is very suitable for applying to Cu(In, Ga)Se<sub>2</sub>-based solar cell.