Obtención de contactos de tipo CuxTe en celdas solares de CdTe mediante depósitos de Te por la técnica de CSVT y evaporación de Cu

Abstract

CdS/CdTe thin films solar cells are composed by direct transition semiconductor compounds, the active element (CdTe) has a high absorption coefficient and most of the production process of this solar cells, can be done in CSVT-HW system (Closed Spaced Vapour Transport - Hot Wall). In this system, are obtained films with good crystalline quality, and high deposition rate, in the order of micrometers per minute, making this system ideal for the manufacture of CdS / CdTe solar cells. The industrial activities around the world are focused on the implementation high quality and low cost production processes. The back contact in CdS/CdTe solar cells needs to be improved. T. Potlog and X. Wu groups have been focusing much of its efforts to obtain a p+ region in CdTe for the subsequent evaporation of a metal as contact. In our group we dominate the creation of a p+ region; it is obtained by varying the physical and chemical stoichiometry of CdTe, for the contact formation. In this thesis work, we explore the production of a compound that plays the function of back contact in CdS/CdTe solar cells. We focus on obtain Cu1.4Te chalcogenide. We achieved the formation of this chalcogenide by the tellurium deposition and copper evaporation on glass; depending on heat treatment and the proportions Cu/Te different chalcogenides of copper was obtained. The next step was the preparation of this compound on CdTe. The CdTe is a p-type semiconductor by tellurium excess, so if we can increase the amount of tellurium in the grains or in grain boundaries we could get a p+ CdTe, this was achieved. The deposition of a thin film of tellurium decreases the resistivity of CdTe. Over this region, rich in tellurium we evaporated copper; in this step was investigated the minimum amount of copper required for the formation of the compound wanted. The samples were subjected to different annealing and outcomes were assessed. Cu1.4Te is a linear, ohmic contact; its specific resistance is influenced by the high CdTe resistivity. In this thesis we have optimized the technological process for CdS/CdTe solar cells back contact formation.