Low power density 980 nm-driven ultrabright red-emitting upconversion nanoparticles via synergetic Yb3+/Tm3+ cascade-sensitization

Herein, we report the first example of synergetic Yb³⁺ → Tm³⁺ → Er³⁺ cascade-sensitized ultrabright red-emitting upconversion nanoparticles with high quantum yield under low power density excitation at 980 nm.