Screening of Broadband Near-Infrared Cr³⁺-Activated Phosphors Using Ce³⁺ as a Probe

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are ideal miniaturized NIR light sources, but it is still difficult to find broadband-emitting NIR phosphors due to the lack of appropriate material design principles. In this work, we propose a method to find hosts yielding broadband NIR Cr³⁺ emission by screening Ce³⁺-doped phosphor hosts for which both Ce³⁺ and Cr³⁺ can occupy the same crystallographic site. A NIR phosphor Ba₃Sc₄O₉:Cr³⁺ (BSO:Cr³⁺) with an emission peak at 835 nm and a full width at half-maximum (FWHM) of 188 nm is obtained, where Ce³⁺ or Cr³⁺ is accommodated at the same Sc³⁺ site. The BSO:Cr³⁺ ceramic is demonstrated to produce a NIR emitter with an output power of 14.56 mW when driven by a blue laser diode at 5.0 V/100 mA. By following the proposed method, two broadband NIR phosphors composed of Li₃Sc₂(PO₄)₃:Cr³⁺ (λ_em = 1000 nm, FWHM = 223 nm) and Na₃Sc₂(PO₄)₃:Cr³⁺ (λ_em = 895 nm, FWHM = 184 nm) are further discovered.