Optimisation of CdS-TCO bilayers for their application as windows in photovoltaic solar cells

The influence of CdS thickness and TCO deposition condition on the optoelectronic, morphological and structural properties of CdS-TCO bilayers has been studied. CdS was deposited by chemical bath, whereas the TCOs (ITO and aluminium-doped ZnO) were prepared by rf-magnetron sputtering. Cadmium sulphide thicknesses below 0.1 mu m have been found to be optimal for avoiding optical absorption losses and conductivity deterioration. Though both types of window coatings, with TCO made at 25 and 200 degrees C, have good quality, the ITO-based samples have shown a higher infrared transmission than those based on ZnO. Additionally, 10 and 70 minutes air-annealing treatments at 200 degrees C have been carried out. Their analysis has demonstrated that the shorter ones are more suitable for enhancing crystalline structure maintaining unchanged electrooptical characteristics.