Design of deep-red persistent phosphors of Gd_3Al_5-xGa_xO_12:Cr^3+ transparent ceramics sensitized by Eu^3+ as an electron trap using conduction band engineering

We developed bright deep-red persistent phosphors of Cr3+-Eu3+ co-doped Gd3Al5-xGaxO12 garnet (GAGG:Cr3+-Eu3+), in which only Cr3+ ion shows emission bands centered at 730 nm after ceasing UV illumination and Eu3+ ion acts as an excellent electron trap capturing one electron to be Eu2+ with tunable trap depth by varying conduction band with Ga3+ content, x. The persistent radiance of the GGG:Cr3+-Eu3+ (x = 5) sample at 1 h after ceasing UV light is approximately 25 times higher than that of the Cr3+ singly doped GGG sample, and is over 6 times higher than that of the widely used ZnGa2O4:Cr3+ red persistent phosphor.