Ca18Na3Y(PO4)14:Eu2+,Mn2+: a novel single-phase dual-emission phosphor and its spectral modulation by Mg2+ for plant lighting and WLEDs

Abstract

Artificial light sources have a significant impact on the cultivation of houseplants. In this work, a novel single-phase dual-emission phosphor, Ca₁₈Na₃Y(PO₄)₁₄:Eu²⁺,Mn²⁺ (CNYPO:Eu²⁺,Mn²⁺), was synthesized and the emission spectra were modulated by co-doping of Mg²⁺ to better match the absorption of plants. The occupancies of Eu²⁺, Mn²⁺ and Mg²⁺ are analyzed by using the data of bond length from XRD Rietveld refinements and the emission spectra. The energy transfer process from Eu²⁺ to Mn²⁺ is proved through the photoluminescence spectra and decay curves. Benefiting from the efficient energy transfer, two broadband emissions peaking at 500 and 650 nm can be achieved, which meets the requirements of plant growth, and the luminescence colour can be tuned from cyan to white and finally to red by changing the ratio of Mn²⁺ to Eu²⁺. The internal quantum efficiency of CNYPO:0.18Eu²⁺,0.18Mn²⁺ is 76.8% under 340 nm excitation. The introduction of Mg²⁺ can regulate the occupation sites of Eu²⁺ and the emission peak position, improve the responsiveness to the plant absorption spectra, and tune the luminescence colour to white. Finally, a white light-emitting diode (WLED) device fabricated using CNYPO:0.18Eu²⁺,0.18Mn²⁺,2.16Mg²⁺ on a 365 nm chip has a high colour rendering index of 89.0 and a low correlated colour temperature of 3580 K, indicating that the prepared phosphor has potential applications in plant lighting and WLEDs.