Mechanistic Insight into Energy‐Transfer Dynamics and Color Tunability of Na<sub>4</sub>CaSi<sub>3</sub>O<sub>9</sub>:Tb<sup>3+</sup>,Eu<sup>3+</sup> for Warm White LEDs
Jin He, Cheng Yan, Minmin Huang, Rui Shi, Yibo Chen, Chris D. Ling, Zhao‐Qing Liu
Abstract
Abstract In this work, a latent energy‐transfer process in traditional Eu 3+ ,Tb 3+ ‐doped phosphors is proposed and a new class of Eu 3+ ,Tb 3+ ‐doped Na 4 CaSi 3 O 9 (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron‐transfer energy process. Relative to other Eu 3+ ,Tb 3+ ‐doped phosphors, the as‐synthesized Eu 3+ ,Tb 3+ ‐doped NCSO phosphors show improved large‐scale tunable emission color from green to red upon UV excitation, controlled by the Tb 3+ /Eu 3+ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu 3+ –O 2− charge‐transfer energy, 4f–5d transition energies, and the energies of 4f excited multiplets of Eu 3+ and Tb 3+ with different 4f N electronic configurations. The Tb 3+ →Eu 3+ energy‐transfer pathway in the co‐doped sample was systematically investigated, by employing luminescence decay dynamics analysis to elucidate the relevant energy‐transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white‐light‐emitting diode (WLED) device was successfully fabricated by using the yellow luminescence NCSO:0.03Tb 3+ , 0.05Eu 3+ phosphor with high thermal stability and a BaMgAl 10 O 17 :Eu 2+ phosphor in combination with a near‐UV chip. These findings open up a new avenue to realize and develop multifunctional high‐performance phosphors by manipulating the energy‐transfer process for practical applications.