Thermally Stable Tb³⁺/Eu³⁺-Codoped K_0.3Bi_0.7F_2.4 Nanoparticles with Multicolor Luminescence for White-Light-Emitting Diodes

A new series of Tb3+-doped and Tb3+/Eu3+-codoped K0.3Bi0.7F2.4 nanoparticles were rapidly synthesized at low temperature. Upon near-ultraviolet light excitation, the Tb3+-doped K0.3Bi0.7F2.4 nanoparticles emit Tb3+ ions’ emission and the intensity is sensitive to the Tb3+ ion concentration, in which the optimal doping content is 9 mol %. Moreover, under 376 nm irradiation, dazzling color-tunable (i.e., from green to yellow and finally to red) emissions are gained in the Tb3+/Eu3+-codoped K0.3Bi0.7F2.4 nanoparticles with the increasing Eu3+ ion content owing to the efficient energy transfer (ET) between Tb3+ and Eu3+ ions. Through theoretical analysis based on the recorded emission spectra and decay time, one knows that the ET in the resultant nanoparticle is efficient and its mechanism is dominated by dipole–dipole interaction. Furthermore, the internal and external quantum efficiencies of the final products are as high as 50.8 and 15.5%, respectively. Aside from the satisfactory photoluminescent behaviors, the developed nanoparticles also exhibit splendid thermal stability, in which the activation energies of Tb3+ and Eu3+ ions in the selected host are 0.26 and 0.23 eV, respectively. Additionally, via the use of the resultant nanoparticles acting as yellow-emitting components, we packaged a white-light-emitting diode (LED), which is able to emit glaring white light with an appropriate corrected color temperature (5854 K) and high color-rendering index (90.1). These findings imply that Tb3+/Eu3+-codoped K0.3Bi0.7F2.4 nanoparticles may serve as potential multicolor-emitting converters for white-LED applications.