Small Stokes Shift Induced Highly Efficient and Thermally Stable Broadband Near‐Infrared Antimonite Double Perovskite Emitters for Spectroscopy Applications

The exploration of efficient broadband portable near-infrared (NIR) light sources is crucial for next-generation NIR spectroscopy-based technologies. However, developing thermally stable and highly efficient NIR photonic materials exceeding 830 nm is met with limited success. Here, a series of broadband NIR phosphors with long-wavelength emission (λ_em > 830 nm) is designed by incorporating activator Cr³⁺ ions into ALaMgSbO₆ (A = Ca, Sr) double perovskite matrices. Specifically, a cation site substitution strategy is proposed to reduce the Stokes shift of ALaMgSbO₆:Cr³⁺ (A = Ca, Sr), rendering these as-prepared NIR phosphors possess excellent thermal resistance performance (89.80%@423 K) and high quantum efficiency (82.5%) simultaneously. Structural analyses, DFT calculations, and spectroscopy measurements revealed that Cr³⁺ ions can occupy both [SbO₆] and [MgO₆] polyhedral sites but prefer to replace Sb⁵⁺ ions in ALaMgSbO₆ (A = Ca, Sr). The luminescence efficiency and thermal stability of the samples are further improved through a flux strategy, and the emission spectra are effectively broadened by the introduction of Yb³⁺ as an extra NIR emitter. Furthermore, the designed phosphors exhibit a full visible-spectrum conversion ability from 400 to 800 nm, showing great promise for versatile NIR spectroscopy applications in solar energy harvesting, night vision, non-destructive visualization, and dental analysis.