Tailoring of polychromatic emissions in Tb3+/Eu3+ codoped NaYbF4 nanoparticles via energy transfer strategy for white light-emitting diodes

Abstract

The polychromatic emission and wide-range color tuning in the luminescent nanoparticles are currently of crucial importance, due to the development of color and white light-emitting diode (LED) devices, based on such lanthanide-doped nanostructured materials. By utilization of precipitation method, Tb3+-doped and Tb3+/Eu3+-codoped NaYbF4 nanoparticles (i.e. NPs) are synthesized. For Tb3+-doped NaYbF4 NPs excited by 377 nm, green emission originating from Tb3+ is observed, where its optimum state is obtained when Tb3+ content is 25 mol% and the concentration quenching mechanism is found by electric dipole-dipole interaction. Moreover, due to the existence of energy transfer between Tb3+ and Eu3+, polychromatic emissions are realized in Tb3+/Eu3+-codoped NaYbF4 NPs as Eu3+ content increases. Through analyzing emission decay times and emission spectra, it was confirmed that the energy transfer mechanism in the synthesized NPs is governed mainly by electric dipole-dipole interaction. Furthermore, the resultant NPs also own strong resistance to temperature, which is verified by temperature-dependent emission spectra, and the activation energies of Tb3+ and Eu3+ are 0.206 and 0.207 eV, respectively. In addition, by employing designed NPs as yellow-emitting components, the fabricated white-LED emits brightness warm white light with color coordinate of (0.385, 0.380), high color rendering index of 84.3 and low correlated color temperature of 3903 K. This work does not only offer an available route to develop NPs with polychromatic emissions but also devise promising luminescent materials for improving the performance of the phosphor-converted white-LED.