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The solar cells were fabricated using layers ITO/ZnO/CdS/CdTe . Films of ZnO and CdS were deposited by rf-sputtering. The CdTe film was grown by the conventional technique of closed space sublimation (CSS). The cells were activated by using the following gases: argon, CHClF 2 -argon and CHClF 2 -argon-oxygen. The last gas improves the J SC and V OC . Cu (15 nm) and Mo (500 nm) used as back contact were deposited by rf-sputtering.

Photoluminescence (PL) spectroscopy was used to study the influence of the CdCl 2 annealing time on the CdTe/CdS solar cell structures. The intensity of the PL peaks related to the CdTe and CdS regions drastically changes after chlorine activation. Regardless of the annealing time of the treatment process, the intensity of the CdTe PL-related defect band increases and the CdS-associated PL emission is reduced due to partial consumption of the CdS layer. It was observed that an increase of the annealing time leads to a redshift of the emission around 1.9 eV related to the inclusion of Te into the CdS layer. Additionally, as annealing time increases, a shoulder, which we correlate with intermixing region, appears around 1.55 eV and reaches its maximum intensity for an annealing time of 60 min. The PL measurements were correlated with the electrical characteristic of the solar cells fabricated with this heterostructure. It was observed that after 60 min of annealing time, there was an increase in both the open circuit voltage (V OC ) and the short circuit current (J SC ), but for higher annealing times these parameters were reduced, decreasing the efficiency of the solar cell.

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