Energy Transfer Engineering Enabled Efficient and Broad-Band Near-Infrared Emission

Near-infrared (NIR) light is crucial for medical diagnostics, industrial inspection, and military applications, but achieving both broad-band and efficient NIR luminescence remains challenging. Here, we propose an energy transfer strategy in low-dimensional halides to enable efficient NIR emission, exemplified by zero-dimensional Cs4CaI6:Yb2+,Sm2+. The optimized Cs4CaI6:1%Yb,3%Sm single crystals exhibit high internal and external quantum efficiencies of 73.3% and 47.8% in the NIR region, respectively, resulting from effective Yb2+→Sm2+ energy transfer. When integrated with a commercial blue-light-emitting chip, a record NIR photoelectric conversion efficiency of 31.0% is achieved. Moreover, Cs4CaI6:1%Yb,3%Sm exhibits an exceptional scintillation efficiency of 52,000 photons/MeV, representing a state-of-the-art performance among NIR scintillators. Its bright NIR scintillation enables clear imaging with polydimethylsiloxane-based scintillation screens, even under ambient light conditions, paving the way for portable outdoor X-ray imaging. This work provides an effective approach to achieve NIR emission for light-emitting diodes and scintillation applications.