“…Sci. 2021, 11, 10879 2 of 14 Yb 3+ :Gd 3 Ga 5 O 12 (GGG) [20], (Yb x Y 1−x ) 3 (Sc 1.5 Ga 0.5 )Ga 3 O 12 (YSGG) [21], Yb 3+ :Lu 3 Ga 5 O 12 (LuGG) [22]), tungstates (e.g., Yb 3+ :KGd(WO 4 ) 2 (KGW) [23,24], Yb 3+ :NaY(WO 4 ) 2 (NaYW) [25], Yb 3+ :NaGd(WO 4 ) 2 (NaGdW) [26], Yb 3+ :KLu(WO 4 ) 2 (KLuW) [27]), and borates (Yb 3+ :YCa 4 O(BO 3 ) 3 (YCOB) [28][29][30], Yb 3+ :GdCa 4 O(BO 3 ) 3 (GdCOB) [28,31]). Among them, Yb 3+ -doped borates with short bond lengths (e.g., Yb:YCOB and Yb:GdCOB) have relatively smaller emission cross-sections (~0.5 × 10 −20 cm 2 ), longer fluorescence lifetimes (~2 ms), broader emission spectra (45 nm), and have been proven to be excellent energy storage materials.…”