The role of CdS preparation method in the performance of CdTe/CdS thin film solar cell

A study of CdS films and how they can influence the CdS/CdTe solar cell interface is reported. CdS is prepared by two different methods. The first one is the closed-space-sublimation (CSS) and the second one is sputtering. Both methods, if they are used properly, are suitable to prepare cells with efficiencies larger than 14%. We found out that, in order to obtain high efficiency cells, CdS prepared by CSS has to be made in presence of O/sub 2/, while CdS prepared by sputtering has to be made in presence of fluorine. In both cases the films need to be washed in acetic acid or annealed at 400-420/spl deg/C in an atmosphere containing H/sub 2/. Both treatments seem to be effective in removing an insulating surface layer, which is formed during the CdS preparation. This insulating material could behave as a good passivant for the CdS grain boundaries.