CdCl2 Activation of the ZnTe:As Back Contact Layer in CdTe Thin Film Solar Cells, Employing a CdS Sacrificial Layer

Incorporating ZnTe:As back contact to CdTe thin film solar cells is an attractive alternative to Cu treated ZnTe back contacts, getting rid of Cu diffusion and subsequent long term stability issues. However, the Zn loss by the formation of volatile ZnCl2 during CdCl2 deposition heat treatment for the back-contact activation remains a challenge. The aim of this work is to develop an effective activation process for ZnTe:As back contacts, which is expected to improve CdTe solar cell efficiencies. To minimize Zn loss, a thin CdS sacrificial cap layer was evaluated which was deposited on ZnTe:As via MOCVD prior to the contact layer activation step.