Presence of the irregular oxidation state of Bi4+ and single-element white emission in YAl3(BO3)4:Bi

Abstract

In typical single-composition white phosphors, various doping elements account for different emission wavelengths. However, it is challenging to tune the doping ratio, and the coexistence of different activators can lead to energy overlap issues. Obtaining white light emission with a single doping element can solve this problem, but it is highly challenging to obtain white light emission via single-element doping. Herein, we report the single-composition white emission phosphor YAl₃(BO₃)₄:Bi with three primary color emissions. YAl₃(BO₃)₄:Bi phosphors have three emission bands of 350–500 nm, 500–590 nm and 590–750 nm under the excitation of 286 nm UV light. Based on the crystallographic, photoluminescence, XPS and EPR data, both Bi³⁺ and diluted Bi⁴⁺ are present in the YAl₃(BO₃)₄:Bi phosphor, leading to three emission bands. The exotic oxidation state of Bi⁴⁺ is stabilized through a cation-deficiency approach. The discovery of single-composition white phosphors with solely Bi doping opens up opportunities for next generation white emission phosphors, and the realization of the Bi⁴⁺ oxidation state through cation-deficiency is a novel approach for stabilization of exotic oxidation states.