Composition-Structure-Luminescence and Enhancement of Cr3+ Activated Broadband Infrared Phosphors for Night Version, Bio-Imaging, and Noninvasive Detection

In the construction of novel near-infrared (NIR) radiation sources, NIR phosphors equipped with broadband emission, and thermally stable are highly desired. In this work, we designed and prepared a series of Cr3+ activated and Cr3+/Yb3+ co-activated KScP2O7 (KSPO) phosphors, with their composition-morphology-structure properties and interaction mechanism systematically investigated. Excited by 475 nm, KSPO: 0.03Cr3+ can emits 700-1200 nm NIR light peaking at 873 nm with a full width at half maximum (FWHM) of 163 nm corresponding to the 4T2→4A2 transition among Cr3+ ions. Cr3+ ions occupy solo crystal site with a weak local crystal-field environment is verified to be responsible for the NIR broadband emission. With the addition of Yb3+, extra NIR emission peaking at 968 nm was obtained as results of the 2F5/2→2F7/2 transition of Yb3+ ions. The internal quantum yield (IQE) was improved from 27.3% of KSPO: 0.03Cr3+ to 40.5% of KSPO: 0.03Cr3+, 0.004Yb3+ phosphor via the energy transfer (ET) of Cr3+→Yb3+. The fabricated NIR pc-LED, utilizing KSPO: 0.03Cr3+, 0.004Yb3+ phosphor and a 470 nm LED chip, exhibits a high output power (37.56 mW@320 mA). Present work suggests that KSPO: 0.03Cr3+, 0.004Yb3+ phosphor has promising application values in night-version, bio-imaging, and noninvasive detection.