In situ deposition of cadmium chloride films using MOCVD for CdTe solar cells

This paper reports on the first deposition of cadmium chloride (CdCl2) films by metal organic chemical vapour deposition (MOCVD). As the p–n junction can be deposited by MOCVD, the in situ CdCl2 treatment of the device allows for containment of the whole process. MOCVD allows a high level of control over material properties and excellent repeatability. Deposition of CdCl2, on glass and silicon, at different II:VII precursor ratios and substrate temperatures are reported. The precursors used are dimethylcadmium and tertiarybutylchloride or n-hexylchloride, respectively for the cadmium and chlorine species. Results are presented on the surface morphology and layer structure. CdCl2 was in its hydrate form once exposed to ambient air. Preliminary results on the effects of in situ CdCl2 treatment on MOCVD CdS/CdTe:As devices are reported and compared with untreated devices, using current–voltage characterisation. The CdCl2 treatment successfully resulted in MOCVD devices having open-circuit voltage higher than 600 mV and fill factor above 50%.