Negligible concentration quenching in photoluminescent nanocrystals with high photoactive rare-earth concentrations: silica–(Tb,Ce)PO4 transparent glass-ceramic green phosphors

Abstract

Rare-earth (RE) orthophosphates of the form REPO₄ are compounds with high RE concentrations (1.3–1.6 × 10²² cm⁻³) and small distances between adjacent RE sites (∼0.4 nm). Transparent sol–gel-derived silica glasses containing Tb-rich (Tb,Ce)PO₄ nanocrystals exhibited bright green photoluminescence from Tb³⁺ ions with internal quantum efficiencies close to unity upon ultraviolet photoexcitation of Ce³⁺ ions. The maximum external quantum efficiency was ∼0.95 and emissions from Ce³⁺ ions were absent. Negligible concentration quenching was achieved by eliminating quenching centres in the nanocrystals in which the rapid migration of excitation energy over Tb³⁺ ions is unrestrained.