Molten Salt Synthesis of Broad-Band Near-Infrared InBO<sub>3</sub>:Cr<sup>3+</sup> Submicron Phosphor and Its Luminescent Enhancement by Lanthanide Ion Codoping
Meiling Shi, Qiyue Shao, Leqi Yao, Shijie Yu, Yan Dong, Jianqing Jiang
Abstract
Phosphor materials with small particle sizes and high luminescent efficiency are desired for the fabrication of phosphor-converted light-emitting diodes (pc-LEDs). Near-infrared (NIR) pc-LED light sources have great application potential in the food industry and medical fields, which stimulate the extensive exploration of NIR phosphors. In this work, broad-band NIR-emitting InBO3:Cr3+ phosphors with submicron size and spherical morphology are successfully synthesized via the molten salt method. The InBO3:Cr3+ phosphor exhibits a broad emission band covering 700–1000 nm and peaking at ∼820 nm. The maximum emission intensity is obtained for InBO3:0.02Cr3+ with an internal quantum yield (IQY) of ∼62%, which is higher than that of microsized counterparts derived from solid-state reaction. Furthermore, the absorption and emission enhancements are achieved by codoping lanthanide ions into InBO3:Cr3+ submicron phosphors. The codoping of inert La3+ ions can increase the absorption efficiency of InBO3:Cr3+, due to the increased octahedral distortion of Cr3+ sites. The codoping of active Yb3+ ions can significantly enhance the NIR emissions of InBO3:Cr3+ between 950 and 1100 nm. Meanwhile, the increased IQY of ∼73% is achieved for InBO3:0.02Cr3+,0.005Yb3+ simultaneously with suppressed thermal quenching, originating from the effective energy transfer from Cr3+ to Yb3+ ions.