Blue Light Excitable Near-Infrared Luminescence Material Yb2–2xCr2xW3O12: Cr3+ → Yb3+ Energy Transfer, Mechanisms of Antithermal Quenching, and High-Performance pc-LED Applications

To overcome the problem of severe thermal quenching (TQ) of near-infrared (NIR) phosphors, the NIR phosphor with antithermal quenching performance is urgently needed. In this work, a negative thermal expansion (NTE) material Yb2–2xCr2xW3O12 was prepared. Through a comprehensive analysis involving in situ X-ray diffractometer (XRD), thermogravimetry (TG), and Rietveld refinement, it was concluded that, at room temperature, the sample adopts a trihydrate orthorhombic structure (Yb2W3O12·3H2O) and does not exhibit negative thermal expansion (NTE) behavior. However, after dehydration at 373 K, anhydrous orthorhombic Yb2W3O12 (space group Pbcn), which exhibits obvious NTE properties, was obtained. The underlying mechanism is that when water molecules enter the crystal and occupy vacancies, the Yb–O–W bonds bend, restricting the transverse thermal vibrations of the Yb–O–W bonds. The characteristic emission of Yb3+ within the range of 800–1300 nm was observed under 468 nm blue light irradiation due to the efficient energy transfer from Cr3+ → Yb3+. Remarkably, the prepared NIR phosphor has antithermal quenching performance, and at 398 K, the intensity of the strongest emission can maintain 1.89 times that of the room temperature, surpassing most NIR phosphors. The antithermal quenching phenomenon is attributed to cell contraction, which reduces the distance between the sensitizer and activator, thereby enhancing the energy transfer efficiency and increasing the luminous intensity. The combination of 460 nm excitable strong NIR emission and antithermal quenching suggests potential application in biomedical imaging and infrared night vision technologies. The NIR pc-LED device, prepared by coating the Yb1.94Cr0.06W3O12 phosphor on a commercial 460 nm chip, demonstrated a high optoelectronic efficiency and high output power, making it well-suited for night vision applications. Furthermore, the efficient NIR-I/II emission from Yb1.94Cr0.06W3O12 was proved to be highly effective for compositional analysis. This study offers valuable insights for designing NIR phosphors with excellent thermal quenching resistance.