An efficient green phosphor of Ce3+ and Tb3+-codoped Ba2Lu5B5O17 and a model for elucidating the high thermal stability of the green emission

Abstract

Green phosphors codoped with Ce³⁺ and Tb³⁺ have been studied extensively for application in UV-based white LEDs, but only few of them show both high luminescence efficiency and thermal stability. This study reports a new green phosphor of Ce³⁺ and Tb³⁺-codoped Ba₂Lu₅B₅O₁₇ prepared by a solid-state reaction. Emission color tuning from blue to green was studied as a function of Tb³⁺ concentration under UV excitation and well-described based on energy transfer from Ce³⁺ to Tb³⁺. The Tb³⁺ emission endowed the green phosphor with a high quantum yield of 86%, and a high thermal stability over the 303–483 K range was achieved. A model has been proposed to explain a general phenomenon observed in Ce³⁺ and Tb³⁺-codoped phosphors that Tb³⁺ emission is thermally more stable than the Ce³⁺ emission. A relationship between the temperature dependencies of Tb³⁺ and Ce³⁺ emissions was obtained in connection with room temperature energy transfer efficiency. The thermally stable Tb³⁺ emission was well-predicated using the obtained relationship. The new phosphor was employed for fabricating a UV-based white LED. A high color-rendering index of 91.4 at a low correlated color temperature of 3809 K is obtained, indicating promising application of Ba₂Lu₅B₅O₁₇:Ce³⁺,Tb³⁺ in solid-state lighting.