Visible Light Excited Yb3+-Doped Phosphor Via Eu2+ Bridged Energy Transfer Toward NIR-II Spectroscopy Application

Yb³⁺ is regarded as an efficient near-infrared-II (NIR-II) emitting activator, which has been widely used in energy conversion, up-conversion luminescence and optical communication. However, the simple energy level structure of Yb³⁺ makes it can only be excited by ultraviolet or infrared light, which limits their application in the currently booming phosphor converted NIR-II light emitting diodes (NIR-II pc-LEDs). Here, “Eu²⁺ bridge” strategy is presented to largely extend Yb³⁺ absorption to visible range, and successfully realize efficient visible light pumped NIR-II emission via energy transfer from Eu²⁺ to Yb³⁺. Meanwhile, to balance the valence state of reduced Eu²⁺ and oxidized Yb³⁺, the pre-prepared EuS is used as precursor instead of Eu₂O₃, which significantly increases the NIR-II luminescence of Yb³⁺ by 6 times. Detailed energy transfer and luminescence enhancement mechanism are discussed. Finally, a NIR-II pc-LED is fabricated with photoelectric efficiency of 12.61%@50 mA and output power of 74.09 mW@300 mA. Subsequently, a miniaturized and real-time test system is integrated based on the convolutional neural network technology to accurate predict organic solvents with different concentrations. This study not only introduces a new strategy to realize visible light-excited Yb³⁺-doped NIR-II emitting phosphors, but also promotes their innovative application based on NIR spectroscopy technology.