Far-red-emitting YAl3(BO3)4:Cr3+ phosphors with excellent thermal stability and high luminescent yield for plant growth LEDs

Phosphors-converted LEDs (pc-LEDs) are excellent artificial light sources for indoor plant cultivation, in which the far-red-emitting component (700-780 nm) plays an important role in regulating the photomorphogenesis of plants. Accordingly, highly efficient and thermally stable far-red-emitting phosphors are indispensable for developing high-performance plant cultivation pc-LEDs. Herein, far-red-emitting YAl3(BO3)(4):Cr3+ (YAB:Cr3+) phosphors were synthesized by solid-state reaction, and their photoluminescence characteristics, thermal quenching, quantum yield (QY), and application in pc-LEDs were systematically investigated. The YAB:Cr3+ phosphor has an intense broadband absorption to the blue light, simultaneously exhibiting the sharp-line E-2 emission and the broadband (4) T-2 emission of Cr3+ with a QY of similar to 86.7%. The far-red broadband emissions of YAB:Cr3+ centered at similar to 735 nm show a high resemblance to the active-state (P-FR) absorption of plant phytochrome. Moreover, the YAB:Cr3+ phosphor shows the thermally enhanced luminescence at temperatures of 303-393 K and the near-zero thermal quenching up to 423 K. The anomalous thermal enhancement is attributed to the temperature-dependent repopulation between E-2 and (4) T-2 states. Finally, a pc-LED device was fabricated with the YAB:Cr3+ phosphor and blue chip, exhibiting the light out power of similar to 50.6 mW and energy conversion efficiency of similar to 17.4% at 100 mA drive current, respectively. The exceptional PL features including suitable excitation/emission wavelengths, suppressed thermal quenching and high QY make YAB:Cr3+ phosphors very promising for applications in plant growth pc-LEDs.