The construction of sublattice level energy cluster for promoting UV upconversion emission in tetragonal LiYF4

The preparation of high performance upconversion luminescence materials with stronger shortwave emissions is still a challenge. In this work, the feature of hexagon circles sublattice structure of tetragonal LiYF 4 was revealed, and the sublattice level energy clusters of 4 Yb 3+ -1Tm 3+ were constructed by the substitution of 70 mol% Yb 3+ for Y 3+ in tetragonal LiYF 4 matrix. The sensitizing ions concentration quenching was inhibited by the hexagon circles sublattice structure, and the upconversion luminescence was dramatically enhanced, especially, the UV band emission was enhanced about 20 times and the intensity ratio of UV to blue emissions was improved about 10 folds under the excitation power density of 0.230 W/cm 2 . Photon numbers of upconversion emissions obviously decreased with the increasing of sublattice level energy clusters that the upconversion process of three photons was changed to two steps of two photons process. The upconversion luminescence mechanism of sublattice energy cluster construction was system investigated. The material with high performance of UV and blue UC luminescence can be a well candidate for the applications of photodynamic therapy and photocatalytic, etc. The work may be an inspiration for high efficient UC luminescence materials design and preparation.