NaSrBO$_3$ : Ce, Yb phosphor for NIR emission around 1 $\mu$m

Synthesis and characterization of NaSrBO$_3$ : Ce, Yb phosphor is described. NaSrBO$_3$ : Ce phosphor exhibited characteristic Ce$^{3+}$ emission around 414 nm. Co-doping with Yb$^{3+}$ resulted in near-infrared (NIR) emission around 981 nm. This is attributed to phonon-assisted cooperative energy transfer from Ce$^{3+}$ to two Yb$^{3+}$ ions. Ce$^{3+}\to$ Yb$^{3+}$ energy transfer is proved using a variety of measurements such as dependence of photoluminescence intensity of visible and NIR emissions on Yb$^{3+}$ concentration, excitation spectrum for Yb$^{3+}$, accelerated decay of Ce$^{3+}$ emission after Yb$^{3+}$ codoping, etc. Using lifetime measurements, the efficiency of Ce$^{3+}\to$ Yb$^{3+}$ energy transfer is estimated to be 48.65%.