Finding a novel highly efficient Mn4+-activated Ca3La2W2O12 far-red emitting phosphor with excellent responsiveness to phytochrome PFR: Towards indoor plant cultivation application

Novel Mn4+-activated Ca3La2W2O12 (CLW) phosphors with far-red emission were successfully synthesized by a high-temperature solid-state reaction method. The obtained samples were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), photoluminescence (PL), decay lifetimes, temperature-dependent emission and internal quantum efficiency (IQE). The CLW:Mn4+ phosphors exhibited an intense broad excitation band in the range of 300-600 nm and gave rise to a strong far-red emission peaking at 711 nm between 650 and 800 tun under near-ultraviolet light (360 nm) or blue light (469 nm) excitation. The CIE chromaticity coordinates and full-width at half-maximum (FWHM) are (0.7125, 0.2858) and 39 nm, respectively. The optimal doping concentration of Mn4+ was about 0.8 mol%, and the concentration quenching mechanism was found to be a dipole-dipole interaction for the Mn4+ activators. Importantly, the CLW:0.8% Mn4+ sample had high IQE of as high as 47.9%. Finally, a LED device was fabricated using a 365 nm ultraviolet emitting LED chip combined with the far-red emitting CLW:0,8%Mn4+ phosphors. Since the emission band of CLW:Mn4+ matched well with the absorption band of phytochrome P-FR under the excitation of light in near ultraviolet to blue, thus the CLW:Mn4+ phosphors have potential application in the indoor plant cultivation.