Highly efficient and thermally stable Cr3+-activated silicate phosphors for broadband near-infrared LED applications

A novel broadband near-infrared (NIR) phosphor LiInSi2O6:Cr3+ (LIS:Cr3+) is successfully synthesized via solid-state reaction. Its crystal structure, photoluminescence properties as well as the application in NIR phosphor-converted LEDs (pc-LEDs) are explored. The LIS:Cr3+ phosphor has two absorptions bands centered at similar to 460 and 670 nm, respectively. Under 460 nm excitation, it shows the broadband NIR emission peaking at similar to 840 nm with a full width at half maximum (FWHM) of similar to 143 nm. The optimum Cr3+ concentration is found to be similar to 6 mol%, whereas the intensity decrease at further increased Cr3+ content is attributed to the radiative energy transfer process. The LIS:0.06Cr(3+) phosphor has a quantum yield of similar to 75% and can retain similar to 77% of the initial intensity at 150 degrees C. Highly efficient, thermally stable and broad NIR emissions of LIS:Cr3+ phosphors are caused by the Cr3+ preferential occupancy in [InO6] octahedron with weak crystal field but relatively strong rigidity. The NIR pc-LED is fabricated by combining the LIS:Cr3+ phosphor with the blue LED chip, which has the NIR output power of similar to 51.6 mW and the photoelectric efficiency of similar to 17.8% at 100 mA drive current. The results suggest that LIS:Cr3+ phosphors have great potential for applications in broadband NIR pc-LEDs.