Effects of the incorporation of copper on the micro structure, charge transport and photoelectrical properties of sputtered ZnTe:Cu films

Abstract

Advances in solar cell technology require improving the relevant physical properties of the constituent materials. One important functionality in photovoltaic devices is the efficient charge transport through the cell. Copper-doped zinc telluride (ZnTe:Cu) has been used as contact to cadmium telluride, the light-absorbing layer in photovoltaic devices. Out of the various deposition techniques, radio frequency sputtering is one of the most versatile and widely employed in research laboratories and industry. In this work, is presented a thorough characterization of ZnTe and ZnTe:Cu films grown by sputtering as a function of substrate temperature (Ts = 300 and 350 °C) and copper concentration (1, 3 and 5 at%). Besides the structural (X-ray diffraction), optical (UV-Vis spectroscopy) and electrical (Hall effect) characterizations, the present study included other studies relevant for optoelectronic applications such as photoluminescence, photoconductivity (under constant or transient illumination) and, in order to determine the effect of copper on the work function, Kelvin probe force microscopy was applied to the samples. Our results show important improvements in crystallite size, conductivity and photoconducting properties derived from the incorporation of copper in the ZnTe lattice.