The development of phosphor-converted light-emitting diodes (pc-LEDs) in the second near-infrared window (NIR-II, 1000–1700 nm) represents an important, newly emerging, and dynamic field in NIR spectroscopy. Unfortunately, lacking efficient NIR-II phosphors that can be excited by commercial blue LED chips impedes NIR spectroscopy applications. Herein, a donor–acceptor strategy is developed by introducing Cr3+ sensitizers to greatly enhance the blue-light excitation efficiency of NIR-II-emitting MgO:Cr3+,Ni2+ phosphor. Consequently, a high-eff...