Multiple Strategies to Approach High-Efficiency Luminescence Controllable in Blue/Cyan/Green-Emitting Bi3+-Activated Phosphors

Cyan gap is a major block in achieving high-quality white light-emitting diodes (WLEDs). Hence, a novel cyan-emitting phosphor Sr2GdGaO5/0.02Bi(3+) with optical tuning performance is synthesized based on the local crystal field regulation strategy surrounding the luminescence center. With the substitution of Al3+ for Ga3+, the photoluminescence (PL) spectra of Sr2GdGa1-xAlxO5/0.02Bi(3+) (0 <= x <= 1) phosphors adjust from cyan (466 nm) to blue (450 nm). Moreover, such a Ba2+ doping adjusts the PL spectra of Sr2-xBaxGdGaO5/0.02Bi(3+) (0 <= x <= 0.5) phosphors from cyan (466 nm) to green (482 nm). These phenomena are contributed to the crystal field splitting and nephelauxetic effect. The energy transfer from Bi3+ to Eu3+ is realized by co-doping Bi3+ and Eu3+ ions in the A(2)GdBO(5)/Bi3+ (A = Sr, Ba; B = Ga, Al) host materials, and two single-phase white phosphors Sr2GdGaO5/0.02Bi(3+), 0.05Eu(3+) and Sr1.5Ba0.5GdGaO5/0.02Bi(3+), 0.05Eu(3+) are obtained. Finally, a WLED with high color rendering index (Ra = 93.6) is prepared by using red/green/blue (RGB) phosphors and Sr2GdGaO5/0.02Bi(3+) phosphor, which is higher than that of the WLED prepared by RGB phosphors (Ra = 86.7), indicating that Sr2GdGaO5/0.02Bi(3+) phosphor can close the cyan gap. These results provide multiple strategies in achieving luminescence controllable and WLED.

Automated summary

A novel cyan-emitting phosphor Sr2GdGaO5/0.02Bi(3+) with optical tuning performance is synthesized based on the crystal field regulation strategy. Energy transfer from Bi3+ to Eu3+ is achieved, leading to the preparation of WLED with high color rendering index.