Energy Transfer and Quenching in Sol–Gel‐Derived Silica Glass Green Phosphors Doped with Tb3+ and Ce3+ Ions: Distinct Difference between P‐ and Al‐Codoped Glasses

Abstract

The (Tb,Ce)−P‐codoped silica glasses containing (Tb,Ce)PO4 nanocrystals (silica−(Tb,Ce)PO4 glass‐ceramics) and (Tb,Ce)−Al‐codoped silica glasses are prepared by a cosolvent‐free sol−gel method. They emit bright green photoluminescence (PL) attributed to the 5D4 → 7F j (j = 1 − 6) transition of Tb3+ ions under excitation at 290 nm into the 4f−5d transition of Ce3+ ions. The (Tb,Ce)−P‐codoped silica glass prepared at the P to rare‐earth (RE) molar ratio of 2 exhibits the internal and external PL quantum efficiencies of ≈0.99 and ≈0.95, respectively, and realizes negligible concentration quenching in (Tb,Ce)PO4 nanocrystals with photoactive RE concentration as high as ≈1.5 × 1022 cm−3. Rapid energy migration over Tb3+ ions in these nanocrystals is confirmed by almost complete PL quenching by the intentional dilute doping of quenching centers (Nd3+ ions). The PL quantum efficiencies are much lower in the (Tb,Ce)−Al‐codoped silica glasses, in which RE ions are dispersed. However, the similar Nd3+ doping only mildly decreases the PL quantum efficiency of this type of glass. These phenomena are consistently explained by the different degree of dispersion of RE ions in the (Tb,Ce)−P‐ and (Tb,Ce)−Al‐codoped silica glasses.