Growth and downconversion luminescence of Ho³⁺/Yb³⁺ codoped α‐NaYF₄ single crystals by the Bridgman method using a KF flux

Abstract

Downconversion (DC) luminescence with emission at about 1000 nm under excitation of 448‐nm light in Ho3+/Yb3+ codoped α‐NaYF4 single crystal is realized. The crystal was grown by the Bridgman method using KF as an assisting flux in a NaF‐YF3 system. The energy‐transfer process and quantum cutting (QC) mechanisms are presented through the analysis of the spectra. The energy‐transfer processes of first‐ and second‐order cooperative DC are responsible for the increase of the emission intensity at 1000 nm, and it is the first‐order cooperative DC that is dominant for the DC process. When the Ho3+ concentration is fixed at about 0.8 mol%, the optimal concentration for ∼1000 nm emission is 3.02 mol% Yb3+ in the current research. The energy‐transfer efficiency and the total quantum efficiency are analyzed through the luminescence decay curves. The maximum quantum cutting efficiency approaches to 184.4% in α‐NaYF4 single crystals of 0.799 mol% Ho3+ and 15.15 mol% Yb3+. However, the emission intensity at 1000 nm decreases while the energy‐transfer efficiency from Ho3+ to Yb3+ increases, which may result from the fluorescence quenching between Ho3+ and Yb3+ ions, Yb3+ and Yb3+ ions.

Up-conversion luminescence and near-infrared quantum cutting of Ho3+/Yb3+ co-doped hexagonal NaGdF4 phosphors

“…Although 184.4% quantum cutting efficiency was obtained by adjusting the doping concentration of Yb 3? , its fluorescence quenching effect limited its application in silicon-based solar cells [22]. P. Babu et al prepared the Ho 3?…”

Down- and Upconversion Phenomena in Gd3(Al,Ga)5O12 Crystals Doped with Pr3+ and Yb3+ Ions

“…Interest in downconversion phenomena in crystals and glasses containing Pr 3+ and Yb 3+ ions is stimulated by attempts to enhance efficiencies of solar cells employing the phenomenon of near-infrared quantum-cutting (QC). , In this phenomenon, one high-energy photon of light in the UV-blue region incident on a luminescent material is converted to two infrared photons emitted near 1000 nm. Numerous published papers have been devoted to investigation of downconversion efficiency and the mechanism involved in various hosts double-doped with Yb 3+ –RE 3+ ions (RE = Pr, Er, Tm, Ho). − In particular, various possible mechanisms of quantum-cutting in Pr 3+ –Yb 3+ co-doped oxyfluoride glass ceramics have been considered and the observed downconversion phenomenon has been attributed to one-step energy transfer (Pr 3+ : 3 P 0 → 1 G 4 ) → (Yb 3+ : 2 F 5/2 → 2 F 7/2 ), which results in generation of two infrared photons via the Yb 3+ : 2 F 5/2 → 2 F 7/2 and Pr 3+ : 1 G 4 → 3 H 5 transitions . The enhanced 1 G 4 emission observed in NaLaF 4 :Pr 3+ , Yb 3+ .…”