Enhanced Stability and Brightness through Co-Substitution: Promoting Plant Growth with Green-Excited Deep Red Phosphor Ca_1-zSr_zLi_1-xMg_2xAl_3-xN₄:yEu².

Abstract

The research utilized a strategy of chemical unit co-substitution, successfully developing a novel blue-green to green excited, deep red-emitting phosphor, Ca_1-zSr_zLi_1-xMg_2xAl_3-xN₄:yEu²⁺ (CLA-2xM-zS:yEu, 0≤x≤0.8, 0.003≤y≤0.01, 0≤z≤1), through the replacement of [Li-Al]⁴⁺ by [Mg-Mg]⁴⁺. This phosphor uniquely converts unusable green light to growth-enhancing deep red, optimizing it for outdoor agriculture. Doping with Sr creates traps, causing a redshift in emission peaks, as confirmed by ⁷Li nuclear magnetic resonance (NMR) spectra, indicating Li presence and lattice changes. Ca_0.2Sr_0.8Li_0.5MgAl_2.5N₄:0.005Eu²⁺ (CLAM-0.8S) phosphor maintained high luminescence intensity under extreme conditions of 85 °C/85% RH, demonstrating excellent photoluminescence performance and chemical stability, compared with conventional SrLi_0.5MgAl_2.5N₄:0.005Eu²⁺ (SLMA) and SrLiAl₃N₄:0.005Eu²⁺(SLA). Experimental results surprised that the unique Ca_0.2Sr_0.8Li_0.8Mg_0.4Al_2.8N₄:0.005Eu²⁺ (CLA-0.4M-0.8S) prepared light-converting film, which is mainly excited by green light, demonstrated a 20% increase in optical density of Chlorella compared to the PP film and a remarkable 97.5% increase compared to the control group without any film. These findings suggest that this film has significant potential for applications in outdoor agriculture and other fields.