Efficient and thermally stable broadband near-infrared emission from near zero thermal expansion AlP3O9:Cr3+ phosphors

Abstract

In recent years, near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) have been emerging as a promising compact and efficient NIR light source for a variety of applications such as sensing, bioimaging and food analysis. However, the development of broadband NIR phosphors with both high emission efficiency and excellent photoluminescence (PL) thermal stability is still facing a great challenge. Herein, a blue light excitable AlP₃O₉:Cr³⁺ phosphor with a broadband NIR emission covering 650–1000 nm is presented. In particular, in situ variable-temperature XRD measurements demonstrate that the AlP₃O₉:Cr³⁺ phosphor shows a near zero thermal expansion in the temperature range of 300–423 K, which is beneficial for achieving good PL thermal stability. The experiment shows that ∼91% of the PL intensity is retained at 423 K compared to that at room temperature, verifying our hypothesis. An efficient NIR pc-LED is fabricated by using the AlP₃O₉:Cr³⁺ phosphor and commercial blue diode chips, generating a NIR radiant flux of 29.5 mW at 60 mA drive current. Finally, the NIR pc-LED was successfully used as the light source for identifying spoiled eggs based on the NIR spectroscopic technique. This work provides a strategy to achieve high performance NIR phosphor systems.