Trivalent terbium host-sensitized orthoniobate green phosphor with high luminescence thermal stability for promising backlighting white light-emitting diodes

The development of narrowband green phosphors with high efficiency and stability plays an important role in the designing of high-performance backlight white light-emitting diode (WLED) devices. In this work, trivalent terbium host-sensitized orthoniobate green phosphor, TbNbO₄, has been prepared using the traditional high-temperature solid-state reaction method. The phosphor has a monoclinic structure with the space group C2/c. Besides, the TbNbO₄ is revealed with a direct bandgap structure and the bandgap is determined to be 3.67 eV by first principle calculation. Under 353 nm UV excitation, TbNbO₄ phosphor shows strong and narrow-band green emission with center around 550 nm, attributed to the ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions. Furthermore, the results demonstrated that the phosphor exhibits favorable thermal stability and activation energy, with a notably high activation energy value of 0.24 eV. This observation suggests that the host-sensitized TbNbO₄ phosphor holds potential as narrow-band green-emitting alternative for backlighting white light-emitting diodes (WLED) display application.