(Y,Tb,Eu)2O3 monospheres for highly fluorescent films and transparent hybrid films with color tunable emission

Abstract

(Y,Tb,Eu)₂O₃ monospheres (∼180 nm in diameter), calcined from the precursors synthesized via urea-based homogeneous precipitation, were employed as the building blocks for highly fluorescent films and as the dispersion fillers for transparent polymer films. The oxide spheres, consisting of ∼40 nm grains, simultaneously displayed the green emission of Tb³⁺ at 543 nm and the red emission of Eu³⁺ at 614 nm under 270 nm UV excitation, with the emission color finely tunable from red to yellow and then to green by increasing the Tb content. The efficiency of Tb³⁺ → Eu³⁺ energy transfer was found to be ∼51.7% for (Y_0.95Tb_0.02Eu_0.03)₂O₃. Self-assembling the oxide monospheres produced close-packed phosphor films with transmittance ≥ 80% (600–850 nm region) and an emission intensity ∼6.8 times that of the powder form. Meanwhile, solution casting yielded transparent PVA films dispersed with the monospheres, which exhibit outstanding flexibility, high transmittance of ≥80% (450–850 nm region), and multi-color emission. The outcomes of this work may have wide implications for flexible luminescent devices and packaging and energy conversion materials.