Harnessing the brilliance of Cr3+ doped LaAlO3–Al2O3 phosphors with exceptional responsiveness to far-red phytochrome for plant growth LEDs

Abstract

Perovskite-based materials have recently gained significant attention due to their unique properties. Herein, the deep and far-red-emitting LaAlO3–Al2O3:Cr3+ perovskite-based phosphors with particle sizes of 2–5 μm have been reported for the first time, demonstrating excellent responsiveness to far-red phytochrome. The synthesized phosphors exhibited a sharply defined deep and far-red emission, peaking at 735 nm, and significant absorptions in the violet (∼410 nm) and green (∼565 nm) regions. The distinct lines at 735 nm can be attributed to the robust crystal field effect of surrounding Cr3+ ions, wherein the 3+ oxidation state substitutes smaller-sized Al3+ ions in the [AlO6] octahedral site of the LaAlO3–Al2O3 lattice. The optimized LaAlO3–Al2O3:0.6%Cr3+ phosphor, annealed at 1400 °C, demonstrated exceptional characteristics, including a color purity of 100 %, a prolonged lifetime of 32.26 ms, a high activation energy of 0.501 eV, and an impressive internal quantum efficiency of 68.1 %. Moreover, a prototype of a violet-pumped LaAlO3–Al2O3:0.6%Cr3+ phosphor-coated LED showcased a well-matched emission spectrum with the absorption spectrum of far-red phytochrome, underscoring its significant potential for applications in LED-based plant growth systems.