Growth and characterization of Cd1−xMgxTe thin films for possible application in high-efficiency solar cells

Abstract

Expanded band gap ternary alloys, such as Cd1-xMgxTe, could be beneficial for formation of high-efficiency CdTe solar cells structures, such as multi-junction and electron reflector devices. Cd1-xMgxTe thin films were grown by side-by-side co-evaporation from CdTe and Mg precursors. Optical measurements reveal increased band gap with higher Mg incorporation and lateral band gap grading across the substrate. SEM imaging denotes a grain size decrease with Mg incorporation. XPS analysis indicates Mg directly replaces Cd in the film. TEC10/CdS/Cd1-xMgxTe structures with and without CdCl2 treatment demonstrate photovoltaic diode behavior similar to typical CdS/CdTe devices. LBIC and QE measurements register grading consistent with band gap grading of the film. Although successful, refinement of Cd1-xMgxTe thin film co-evaporation is needed to improve spatial uniformity for large area deposition.