Enhancing Mn4+ luminescence via Y3+ substitution in Sr0.1La0.9Mg0.45Ti0.55O3 double perovskite for advanced horticultural lighting

Abstract

Far-red-emitting phosphors play a pivotal role in horticultural light-emitting diodes (LEDs), as red light is critical for photosynthesis and photomorphogenic regulation in plants. Here, we report the synthesis of a novel series of Mn⁴⁺-doped double-perovskite Sr_0.1La_0.9Mg_0.45Ti_0.55O₃ (SLMTO) phosphors via conventional high-temperature solid-state reactions. The phase purity was confirmed by X-ray powder diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) confirmed the successful incorporation of Mn⁴⁺ ions into the host lattice. Under 365 nm excitation, SLMTO: Mn⁴⁺ phosphor exhibits a sharp far-red emission at 709 nm, corresponding to the ²E_1g → ⁴A_2g transition. Photoluminescence excitation monitored at 709 nm reveals broad band from 200 to 600 nm, indicating effective ultraviolet-visible excitation. Tanabe-Sugano diagram analysis reveals that Mn⁴⁺ ions occupies octahedral sites under a strong crystal field. Further investigations elucidate the crystal field effects, concentration quenching mechanism, and thermal quenching behavior of Mn⁴⁺ ions in the SLMTO host. To boost emission intensity, partial A-site substitution with Y³⁺ was performed, the Y³⁺-doped phosphor achieves an internal quantum efficiency (IQE) of 89.2 %, an activation energy of 0.375 eV, and a color purity of 95.8 %. Notably, the emission profile of the optimized phosphor closely overlaps the far-red absorption band of plant phytochrome far-red light (P_fr). And a far-red light-emitting diode (LED) device by combining the phosphor with a 365 nm LED chip was fabricated, the resulting device demonstrates great potential for plant growth lighting applications.