Near-infrared quantum cutting in Ho3+, Yb3+-codoped BaGdF5 nanoparticles via first- and second-order energy transfers

Infrared quantum cutting involving Yb³⁺ 950–1,000 nm (² F_5/2 → ² F_7/2) and Ho³⁺ 1,007 nm (⁵S₂,⁵F₄ → ⁵I₆) as well as 1,180 nm (⁵I₆ → ⁵I₈) emissions is achieved in BaGdF₅: Ho³⁺, Yb³⁺ nanoparticles which are synthesized by a facile hydrothermal route. The mechanisms through first- and second-order energy transfers were analyzed by the dependence of Yb³⁺ doping concentration on the visible and infrared emissions, decay lifetime curves of the ⁵ F₅ → ⁵I₈, ⁵S₂/⁵F₄ → ⁵I₈, and ⁵ F₃ → ⁵I₈ of Ho³⁺, in which a back energy transfer from Yb³⁺ to Ho³⁺ is first proposed to interpret the spectral characteristics. A modified calculation equation for quantum efficiency of Yb³⁺-Ho³⁺ couple by exciting at 450 nm was presented according to the quantum cutting mechanism. Overall, the excellent luminescence properties of BaGdF₅: Ho³⁺, Yb³⁺ near-infrared quantum cutting nanoparticles could explore an interesting approach to maximize the performance of solar cells.