Efficient sensitization of rare-earth-free Mn4+-activated antimonate phosphor: enabling intense far-red emission for agricultural lighting

Abstract

The employment of red phosphors is an essential component in the fabrication of LEDs tailored for plant illumination with red light, as they serve as a cornerstone in their construction and functionality. In this work, a Mn⁴⁺-activated antimonate phosphor exhibiting far-red emission has been developed. Despite the inherent limitations posed by Mn⁴⁺'s spin-forbidden ²E_g–⁴A_2g transition, the phosphor's UV absorption and far-red emission were significantly enhanced by leveraging the sensitization effect of Bi³⁺, resulting in an impressive internal quantum efficiency of 76.1% under 316 nm UV excitation. Furthermore, at an elevated temperature of 423 K, the phosphor maintains 48.2% of its room-temperature emission intensity, significantly outperforming most Mn⁴⁺-activated antimonate phosphors reported in existing research studies. Importantly, the emission spectrum of this phosphor shows substantial overlap with the absorption spectra of chlorophyll and photochromes commonly found in plants. LED devices encapsulated with this phosphor, when used for supplemental lighting during the cultivation of mustard plants, have demonstrated substantial improvements in both germination rates and phenotypic characteristics. This underscores the exciting prospects of employing this phosphor in agricultural lighting systems for enhanced crop productivity.