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<p>In recent years, Bi<sup>3+</sup> -activated spinel phosphors have attracted growing attention for their potential in high-efficiency lighting. In this study, we unveil the mechanism underlying the enhanced thermal stability of green-yellow-emitting Bi<sup>3+</sup> -doped CaGa<sub>2</sub>O<sub>4</sub> phosphors (CaGa<sub>2</sub>O<sub>4</sub>:Bi<sup>3+</sup>), highlighting a notable negative thermal quenching effect. The synthesized CaGa<sub>2</sub>O<sub>4</sub>:Bi<sup>3+</sup> phosphor exhibits a broad and intense green-yellow emission spectrum, with two distinct peaks at 528&#xa0;nm and 583&#xa0;nm. These bands correspond to the <sup>3</sup>P<sub>1</sub>→ <sup>1</sup>S<sub>0</sub> transitions of Bi<sup>3+</sup> ions occupying the [CaO₇] (C₇) and [CaO₈] (C₈) sites, respectively. Optimal luminescence is achieved with 0.75% Bi<sup>3+</sup> doping and annealing at 1300&#xa0;°C, yielding a high external quantum efficiency of 48.3%, a long lifetime of 0.64 ms, and remarkable thermal stability. Notably, as the measurement temperature increased from room temperature to 423&#xa0;K, the enhancement of photoluminescence intensity increased by 121%, accompanied by a blue shift in the emission peak. This behavior is attributed to the thermally activated electron release from shallow traps and site-selective redistribution, favoring C₇ and C₈ centers. The electron population is found to be preferentially redistributed through the C<sub>7</sub> center compared to the C<sub>8</sub> center. Furthermore, an LED prototype incorporating this optimized phosphor and a 310&#xa0;nm chip demonstrates strong potential for advanced white light-emitting-diode (WLED) applications.</p>

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Enhanced thermal stability of Bi3+-doped CaGa2O4 phosphors for next-gen WLED applications

  • 期刊论文

  • 发表日期：

    2025年11月5日

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  • Tran Khac Khoi,
  • Nguyen Tu,
  • Do Quang Trung,
  • Nguyen Van Du,
  • Nguyen Van Quang,
  • Ta Ngoc Bach,
  • Nguyen Duy Hung,
  • Duong Thanh Tung,
  • Le Tien Ha,
  • Pham Thi Lan Huong,
  • Le Thi Thao Vien,
  • Manh Trung Tran,
  • Nguyen Minh Hieu,
  • Pham Thanh Huy

摘要

In recent years, Bi3+ -activated spinel phosphors have attracted growing attention for their potential in high-efficiency lighting. In this study, we unveil the mechanism underlying the enhanced thermal stability of green-yellow-emitting Bi3+ -doped CaGa2O4 phosphors (CaGa2O4:Bi3+), highlighting a notable negative thermal quenching effect. The synthesized CaGa2O4:Bi3+ phosphor exhibits a broad and intense green-yellow emission spectrum, with two distinct peaks at 528 nm and 583 nm. These bands correspond to the 3P1→ 1S0 transitions of Bi3+ ions occupying the [CaO₇] (C₇) and [CaO₈] (C₈) sites, respectively. Optimal luminescence is achieved with 0.75% Bi3+ doping and annealing at 1300 °C, yielding a high external quantum efficiency of 48.3%, a long lifetime of 0.64 ms, and remarkable thermal stability. Notably, as the measurement temperature increased from room temperature to 423 K, the enhancement of photoluminescence intensity increased by 121%, accompanied by a blue shift in the emission peak. This behavior is attributed to the thermally activated electron release from shallow traps and site-selective redistribution, favoring C₇ and C₈ centers. The electron population is found to be preferentially redistributed through the C7 center compared to the C8 center. Furthermore, an LED prototype incorporating this optimized phosphor and a 310 nm chip demonstrates strong potential for advanced white light-emitting-diode (WLED) applications.