Mechanistic Insight into Energy‐Transfer Dynamics and Color Tunability of Na4CaSi3O9:Tb3+,Eu3+ for Warm White LEDs

In this work, a latent energy-transfer process in traditional Eu3+ ,Tb3+ -doped phosphors is proposed and a new class of Eu3+ ,Tb3+ -doped Na4 CaSi3 O9 (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Relative to other Eu3+ ,Tb3+ -doped phosphors, the as-synthesized Eu3+ ,Tb3+ -doped NCSO phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb3+ /Eu3+ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu3+ -O2- charge-transfer energy, 4f-5d transition energies, and the energies of 4f excited multiplets of Eu3+ and Tb3+ with different 4fN electronic configurations. The Tb3+ →Eu3+ 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:0.03Tb3+ , 0.05Eu3+ phosphor with high thermal stability and a BaMgAl10 O17 :Eu2+ 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.