Enhanced Stability and Brightness through Co‐Substitution: Promoting Plant Growth with Green‐Excited Deep Red Phosphor Ca 1‐z Sr z Li 1‐x Mg 2x Al 3‐x N 4 :yEu 2

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‐z Sr z Li 1‐x Mg 2x Al 3‐x N 4 :yEu 2+ (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 7 Li nuclear magnetic resonance (NMR) spectra, indicating Li presence and lattice changes. Ca 0.2 Sr 0.8 Li 0.5 MgAl 2.5 N 4 :0.005Eu 2+ (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 0.5 MgAl 2.5 N 4 :0.005Eu 2+ (SLMA) and SrLiAl 3 N 4 :0.005Eu 2+ (SLA). Experimental results surprised that the unique Ca 0.2 Sr 0.8 Li 0.8 Mg 0.4 Al 2.8 N 4 :0.005Eu 2+ (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.