Development of ultra-broad band light emitting single phase garnet phosphor based on energy transfer mechanism and its applications in optical temperature sensing and WLED

Cerium (Ce3+) doped garnet phosphor has received much attention for optoelectronic device applications. However, the family of Ce3+ doped garnet phosphors suffers from deficiency of red component in their emission spectrum. Herein, authors present a strategy to improve red component through widening of emission band with the incorporation of Cr3+ co-dopant in the garnet structure. In view of this authors have prepared a series of Ce3+ doped and Ce3+/Cr3+ co-doped Gd3Al4GaO12 (GAGG) garnet using the facile solid state reaction method. The structural studies of prepared garnet is done with the help of X-ray diffraction (XRD) study. The photoluminescence study demonstrates that Ce3+/Cr3+ co-doped garnet sample emits an ultra-broad emission band ranging from 490 nm to 850 nm under suitable excitations. The ultra-broad band is observed due to the combination of emission bands originating from the transitions of Ce3+ and Cr3+. The Ce3+/Cr3+ co-doped garnet sample is also studied to examine the optical thermometric ability with the help of the luminescence intensity ratio (LIR) technique. Finally, the selected samples with optimized compositions GAGG: 6.0 %Ce3+ and GAGG:6.0 %Ce3+/1.5 %Cr3+ were used to fabricate pc-WLED device by the coating of phosphor layer over commercially available blue LED chip (InGaN). The fabricated pc-WLED device has shown good voltage stability as well as good LED performance parameters CRI (>70) and CCT (<4000K) values. Present results may stimulate the exploration of optical tuning via the incorporation of additional dopants such as Cr3+ in Ce3+ doped garnet phosphor for optical thermometry and pc-WLED.