Efficient upconversion luminescence from Ba(5)Gd(8)Zn(4)O(21):Yb(3+), Er(3+) based on a demonstrated cross-relaxation process

Under 971 nm excitation, bright green and red emissions from Yb(3+)/Er(3+) co-doped Ba(5)Gd(8)Zn(4)O(21) phosphor can be observed, especially the intense red emission in highly doped samples. The experimental results indicate that Ba(5)Gd(8)Zn(4)O(21):Yb(3+), Er(3+) emits stronger upconversion luminescence than NaYF(4):Yb(3+), Er(3+) under a low excitation power, and a maximum upconversion power efficiency of 2.7% for Ba(5)Gd(8)Zn(4)O(21):Yb(3+), Er(3+) was achieved. More significantly, to explain the red emission enhanced with the dopant concentration, this paper presents a possible cross-relaxation process and demonstrates it based on the rate equation description and temporal evolution. In view of the strong upconversion luminescence, colour tunable ability and stable chemical nature, Yb(3+)/Er(3+) co-doped Ba(5)Gd(8)Zn(4)O(21) phosphor could be an excellent candidate for efficient upconversion luminescence generation.