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

Expanded band gap ternary alloys, such as Cd_1-xMg_xTe, could be beneficial for formation of high-efficiency CdTe solar cells structures, such as multi-junction and electron reflector devices. Cd_1-xMg_xTe 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/Cd_1-xMg_xTe 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 Cd_1-xMg_xTe thin film co-evaporation is needed to improve spatial uniformity for large area deposition.