NIR light guided enhanced photoluminescence and temperature sensing in Ho3+/Yb3+/Bi3+ co-doped ZnGa2O4 phosphor
Monika, Ram Sagar Yadav, Anita Rai, S. Bahadur
Abstract
Abstract The conversion of NIR light into visible light has been studied in Ho 3+ /Yb 3+ /Bi 3+ co-doped ZnGa 2 O 4 phosphor for the first time. The crystallinity and particles size of the phosphor increase through Bi 3+ doping. The absorption characteristics of Ho 3+ , Yb 3+ and Bi 3+ ions are identified by the UV–vis-NIR measurements. The Ho 3+ doped phosphor produces intense green upconversion (UC) emission under 980 nm excitations. The emission intensity ~ excitation power density plots show contribution of two photons for the UC emissions. The UC intensity of green emission is weak in the Ho 3+ doped phosphor, which enhances upto 128 and 228 times through co-doping of Yb 3+ and Yb 3+ /Bi 3+ ions, respectively. The relative and absolute temperature sensing sensitivities of Ho 3+ /Yb 3+ /5Bi 3+ co-doped ZnGa 2 O 4 phosphor are calculated to be 13.6 × 10 −4 and 14.3 × 10 −4 K −1 , respectively. The variation in concentration of Bi 3+ ion and power density produces excellent color tunability from green to red via yellow regions. The CCT also varies with concentration of Bi 3+ ion and power density from cool to warm light. The color purity of phosphor is achieved to 98.6% through Bi 3+ doping. Therefore, the Ho 3+ /Yb 3+ /Bi 3+ :ZnGa 2 O 4 phosphors can be suitable for UC-based color tunable devices, green light emitting diodes and temperature sensing.