Up-conversion luminescence and near-infrared quantum cutting in Y6O5F8:RE3+ (RE = Yb, Er, and Ho) with controllable morphologies by hydrothermal synthesis

Abstract

Monodisperse and uniform Y₆O₅F₈:RE³⁺ (RE = Yb, Er, and Ho) microarchitectures with various morphologies have been constructed by a facile surfactant-assisted hydrothermal route, and their up-conversion luminescence and NIR quantum cutting properties were investigated. Hollow hexagonal prisms, microbundle gatherings by rods, and solid hexagonal prisms were designed by employing CTAB, PVP, and EDTA as additives, respectively. Under 980 nm excitation, the Y_5.34O₅F₈:0.6Yb³⁺, 0.06Er³⁺ samples obtained using different additives exhibit similar emission spectra profiles with predominating peaks at 670 nm; the Y_5.34O₅F₈:0.6Yb³⁺, 0.06Ho³⁺ samples give green emissions with the strongest peaks around 544 nm. The NIR quantum cutting for the Y₆O₅F₈:Yb³⁺, Ho³⁺ samples was identified by the NIR emission spectra upon both 360 and 450 nm excitation. The corresponding quantum cutting mechanisms were discussed through the energy level diagrams, in which a back-energy-transfer from Yb³⁺ to Ho³⁺ was first proposed to interpret the spectral characteristics. A modified calculation equation for the quantum efficiency of Yb³⁺–Ho³⁺ coupled by exciting at 450 nm was suggested according to the quantum cutting mechanism. The efficient NIR luminescence and quantum cutting in Yb³⁺, Ho³⁺ co-doped Y₆O₅F₈ reveal a possible application in modifying the solar spectrum to enhance the efficiency of silicon solar cells.