Synthesis of high-quality ZnTe:Cu films as a back contact layer for CdTe solar cells

P-type copper-doped zinc telluride (ZnTe:Cu) is a good candidate as a back contact of cadmium telluride (CdTe) solar cell. The deposition rate, transmittance and resistivity of ZnTe:Cu films deposited via target bias radio frequency (r.f.) sputtering was studied. The target bias voltage considerably influenced ZnTe:Cu film resistivity. In the meantime we find that post-deposition heat treatment (PDHT) significantly reduces the electrical resistivity of the ZnTe:Cu films, which is due to increases in both carrier concentration and mobility. It is inspiring for us to further improve the conductivity of ZnTe:Cu by applying the r.f. coupled d.c. sputtering and PDHT.