EFFECTS OF MORPHOLOGIES OF (CD+TE) POWDERS ON THE PROPERTIES OF SINTERED CDS/CDTE SOLAR-CELLS

Polycrystalline CdS/CdTe solar cells have been prepared by coating and sintering a CdS slurry and a (Cd + Te) slurry. CdS layers were first formed on borosilicate glass substrates at 600-degrees-C in nitrogen and then CdTe layers were formed on the sintered CdS layers at 625-degrees-C in nitrogen. The (Cd + Te) slurry contained (Cd + Te) powders mixed in a ball mill for 12-220 h instead of more expensive CdTe powders. The shape of cadmium particles changed from spherical to plate-like and the diameter of the plate-shaped particles became smaller as the ball-milling time increased. In addition, a compound CdTe started to form during a long milling time. The sintered CdTe layers were more compact as the diameter of plate-shaped cadmium particles decreased. However, cracks developed in the sintered CdTe layer when the diameter was small (approximately 2 mum). The efficiency of sintered CdS/CdTe solar cells increased with decreasing particle diameter and then decreased with further decrease in particle diameter. The highest efficiency of 12:1% was achieved using a mixture of (Cd + Te) powders which had plate-shaped cadmium particles with a diameter of 5 mum. The results suggest that high-efficiency sintered CdS/CdTe solar cells can be fabricated by using CdTe slurry from the mixture of (Cd + Te) powders with an inexpensive ball-milling process.