The effect of ion radius on luminescence for alkali ions doping in YO: Yb/Ho thin film.

In this paper, alkali ion (Li Na K and Rb)-doped YO:Yb/Ho up conversion films were prepared using the sol-gel method. The structures of the films were studied by using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy. A series of high-quality thin films with good crystallization were prepared. For all samples, two emission bands were observed: green emission at 539 (550) nm and red emission at 664 nm, which can be attributed to F (S)→I and F→I, respectively. The green emission is dominant, and the red emission is extremely weak. The effect of each alkali-ion dopant on the emission and color adjustment of samples was investigated. The green emission intensity is increased by a factor of 6.33 (Li), 2.03 (Na), 4.82 (K) and 1.92 (Rb) with increasing alkali-ion doping concentration, and red emission is increased by a factor of 7.80 (Li), 1.92 (Na), 4.78 (K) and 1.90 (Rb). The extreme value appears earlier with increasing ion radius. Li doping boosts luminescence in three ways, and the other alkali ions affect the light emission in two ways. Li doping and K doping can be used to adjust the color coordinates towards the 539 nm and 550 nm directions, respectively. Na and Rb doping can enhance emission with a stable color. This means that each alkali ion is a suitable choice as a color-regulating ion and can play a role in the regulation of luminescence.