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

Yb 3+ 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 Yb 3+ 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, “Eu 2+ bridge” strategy is presented to largely extend Yb 3+ absorption to visible range, and successfully realize efficient visible light pumped NIR‐II emission via energy transfer from Eu 2+ to Yb 3+ . Meanwhile, to balance the valence state of reduced Eu 2+ and oxidized Yb 3+ , the pre‐prepared EuS is used as precursor instead of Eu 2 O 3 , which significantly increases the NIR‐II luminescence of Yb 3+ 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 Yb 3+ ‐doped NIR‐II emitting phosphors, but also promotes their innovative application based on NIR spectroscopy technology.