Molten Salt Synthesis of Broad-Band Near-Infrared InBO3:Cr3+ Submicron Phosphor and Its Luminescent Enhancement by Lanthanide Ion Codoping

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 InBO 3:Cr 3+ phosphors with submicron size and spherical morphology are successfully synthesized via the molten salt method. The InBO 3:Cr 3+ phosphor exhibits a broad emission band covering 700–1000 nm and peaking at ∼820 nm. The maximum emission intensity is obtained for InBO 3:0.02Cr 3+ 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 InBO 3:Cr 3+ submicron phosphors. The codoping of inert La 3+ ions can increase the absorption efficiency of InBO 3:Cr 3+, due to the increased octahedral distortion of Cr 3+ sites. The codoping of active Yb 3+ ions can significantly enhance the NIR emissions of InBO 3:Cr 3+ between 950 and 1100 nm. Meanwhile, the increased IQY of ∼73% is achieved for InBO 3:0.02Cr 3+,0.005Yb 3+ simultaneously with suppressed thermal quenching, originating from the effective energy transfer from Cr 3+ to Yb 3+ ions.