Infrared Induced White Anti-stokes Emission of LiYbP₄O₁₂ Nanocrystals

Abstract

Upconversion properties of lithium ytterbium tetraphosphate (LiYbP₄O₁₂) nanocrystals under infrared excitation (976 nm) have been investigated. It has been found that the white color anti-Stokes emission intensity increased over two orders of magnitude with lowering the pressure from atmospheric (~10³ mbar) to vacuum (10⁻⁶ mbar). The dependence of emission intensity on excitation power was characterized by a sigmoidal shape characteristic to avalanche process (see Fig. 43.1b) The anti-Stokes white emission was accompanied with long build up times (see Fig. 43.1a). Moreover significant increase of photocurrent under excitation has been observed. The mechanism of white light generation has been discussed in terms of Yb²⁺- CT luminescence