Effect of CdCl 2 Treatment of CdS Films on CdTe/CdS Solar Cells

We investigated the effect of CdCl 2 treatment of CdS films on the photovoltaic performance of polycrystalline CdTe/CdS solar cells. X-ray diffraction studies indicated that the diffusion of S into CdTe is qualitatively the same for CdTe/CdS films fabricated with both as-deposited and CdCl 2 -treated CdS. A major difference was observed in the extent of Te diffusion into CdS for the two types of CdS films. Full conversion of CdS into CdS 1-y Te y ; was observed for films prepared with asdeposited CdS, while the formation of the ternary phase was below the detection limit for films prepared with CdCl 2 -treated CdS. Photoluminescence measurements confirmed this result. The difference in interdiffusion leads to differences in optical transmission of CdS films and spectral response of CdTe/CdS solar cells. An increase of 2.7 mA/cm 2 in short-circuit current density was observed as a result of improved spectral response in the wavelength range of 500–600 nm for the CdCl 2 -treated CdS.