Broadband down-conversion in Bi3+-Yb3+-codoped yttrium and yttrium-aluminum oxides

Comparative study of the broadband down-conversion processes in Bi3+-Yb3+-codoped yttrium oxide (Y2O3) and various yttrium-aluminum oxides (Y3Al5O12, YAlO3 and Y4Al2O9) has been performed from the point of view of search for materials suitable for enhancement of efficiency of silicon solar cells. The studied materials in the form of nanopowders have been synthesized by sol-gel method and characterized by X-ray powder diffraction, scanning electron microscopy and luminescence techniques. Relative down-conversion efficiency for studied materials has been estimated. It was shown that optimal concentration of Yb3+ ions should be 2-4 at.% simultaneously with Bi3+ ions in the amount of about 1 at.%. Such dopants content provides the highest emission intensity of Yb3+ ions in near-infrared when excited into Bi3+ ions absorption in ultraviolet. Perspectives of the studied materials for enhancement of silicon solar cells are discussed.