Highly efficient adjustable photoluminescence with negative thermal expansion/quenching of SrGa2B2O7: Bi/Na/Tb/Eu for LEDs via synergistic alkali metal ions and Sr/O vacancies regulations

Phosphor with thermally stable and highly efficient photoluminescence (PL) is a premise/challenge for use in high-quality phosphor-converted light-emitting diodes (pc-LEDs). Herein, via a facile solid-phase sintering method in air, a negative thermal quenching (TQ) blue emitting SrGa 2 B 2 O 7 (SGB): Bi is reported, mainly associating with the underlying collaborative effect of negative volumetric thermal expansion of rigid host, heterovalent substitution (Bi 3+ → Sr 2+ )-induced V Sr /V O vacancies, and generating self-reduction ions (Bi 2+ ). For charge balance under the condition of temperature rising, both opposite process of self-oxidation (Bi 2+ to Bi 3+ ) and charge release from trap levels can compensate blue-PL loss. This phosphor is comparable to Eu 2+ /Ce 3+ -activated blue-emitting phosphors, and even boasts superior quantum efficiency (QE) and thermal stability. Via artificially codoping Na + for charge compensation, the QE of the SGB:Bi/Na can be further significantly enhanced. Color-tunable PL is achieved via cascade-connected energy transfer (ET) from Bi 3+ to Tb 3+ (green)/Eu 3+ (red) in SGB: Bi/Na/Tb/Eu that possesses high QE/stability than the case of blue/green/red tricolor phosphor blends adopted in warm white LEDs (wLEDs). Finally, the SGB: Bi/Na and SGB: Bi/Tb/Eu/Na are respectively, encapsulated with distinct encapsulants via either traditional or remote “capping” packaging strategy to form blue LEDs and wLEDs, showcasing splendid electroluminescence behaviors and luciferous application prospects.