Study of Fermi level position before and after CdCl2 treatment of CdTe thin films using ultraviolet photoelectron spectroscopy

The CdCl2 treatment used in the development of high efficiency CdTe solar cells is an essential processing step but remains fully unexplored. What really happens during this treatment is not yet fully understood. The changes in doping concentrations during this processing step are a key parameter to investigate. Determination of the position of the Fermi level (FL) is a good method to explore these changes and therefore photoelectrochemical cell method and ultraviolet photoelectron spectroscopy method have been used to investigate these trends. Four different CdTe layers prepared by electroplating have been used for this investigation. The overall observations indicate the settling down of the FL in the upper half of the bandgap after CdCl2 treatment.