Synthesis and properties of Cd²⁺ co-doped green-emitting Zn₄B₆O₁₃:Mn²⁺ phosphors

The emission wavelength of Mn-activated phosphors is determined by the coordination environment of Mn and the crystal field effect. Under a carbon-reducing conditions, Zn₄B₆O₁₃:5 mol% Mn²⁺, x mol% Cd²⁺ (x = 0, 0.5, 1, 2, 3, 4, 5, 6) green-emitting phosphors were synthesized and investigated. All specimens were verified by X-ray diffraction (XRD) to crystallize in a pure phase. The photoluminescence properties of the samples were systematically investigated, and the results revealed that Cd²⁺ co-doping significantly enhanced the Mn²⁺ emission intensity. At a Cd²⁺ concentration of 4 mol%, the Mn²⁺ emission intensity reached approximately 3.99 times that of the Cd²⁺-undoped sample, while maintaining a favorable luminescence lifetime. Thermal stability tests demonstrated that the phosphors retained excellent emission performance even at 150 °C. A green light-emitting diode was successfully fabricated by combining the synthesized phosphors with a light-emitting diode (LED) chip. Meanwhile, first-principles calculations were performed to explore the electronic band structure and density of states (DOS) of Cd/Mn co-doped Zn₁₆B₂₄O₅₂. The results showed that the introduction of Cd²⁺ and Mn²⁺ reduced the band gap of the host material, while Mn²⁺ doping broke the symmetric distribution of the electronic structure of the system.