The performance of thin film solar cells employing photovoltaic ZnSe/CdTe, CdS/CdTe and ZnTe/CdTe heterojunctions

This paper focuses on the photovoltaic parameters of ZnSe/CdTe, CdS/CdTe, and ZnTe/CdTe thin film heterojunction solar cells. ZnSe/CdTe, CdS/CdTe, and ZnTe/CdTe thin film heterojunction solar cells were fabricated by Close Space Sublimation (CSS) on TCO-coated glass substrates. All types of solar cells were fabricated in a superstrate configuration. The thickness of ZnSe and ZnTe layers was varied in order to adjust the solar cell performance. A similar cadmium chloride solution for the treatment of a CdTe layer with an elevated temperature air annealing of the completed devices before the back contact deposition was applied to ZnSe/CdTe and CdS/CdTe thin film heterojunctions solar cells with exception of ZnTe/CdTe. All cells were characterized through light and dark current density-voltage (J-V) measurements and quantum efficiency (QE) measurements. The saturation current, ideality factor and photovoltaic parameters for all thin film heterojunction solar cells are presented. The investigation at the room temperature under illumination of 100 mW/cm² through the wide gap components of ZnSe/CdTe, CdS/CdTe, and ZnTe/CdTe heterojunctions showed a value of conversion efficiency (η) of solar energy to electric energy about 4.7%, 9.9%, and 1.3%, respectively. The incorporation of Zn at the ZnSe and CdTe interface doubles the short circuit current density and improves the performance of ZnSe/CdTe thin film heterojunction solar cells.