Novel double-perovskite SrLaLiTeO6:Mn4+ far-red phosphor with superior thermal stability for indoor plant growth LED

Abstract A series of red-emitting phosphors SrLaLiTe1-xO6: xMn4+ were prepared via high-temperature solid-state reaction technique. The structure of SrLaLiTeO6 (abbreviated as SLLT) is a typical cubic double-perovskite structure with the space group of Fm-3m (225). Based on the density functional theory (DFT) calculation, the SrLaLiTeO6 presents a direct band gap property with the band gap energy (Eg) of 3.22eV. The estimated Eg of SrLaLiTeO6 and SrLaLiTe0.988O6: 0.012Mn4+ were evaluated to be 3.08 eV and 2.98 eV derived from diffuse reflectance spectra, respectively. The emission spectra show a narrow emission band from 650 nm (15384 cm−1) to 770 nm (12987 cm−1) peaking at 696 nm and 708 nm, which exhibits a greater overlap with the phytochrome (PR and PFR) absorption. Furthermore, the nephelauxetic effect of Mn4+ in the SLLT host were estimated in detail by using the crystal field strength (Dq) and Racah parameters (B, C). Finally, the intensity remained at 79.01% and 81.44% of the original intensity when the temperature was elevated at 423 K, respectively, which illustrates good thermal stability. All these results manifest that SrLaLiTeO6: Mn4+ is expected to be a candidate for indoor plant cultivation LED.