Far-red emitting phosphors for plant growth applications: fitted and enhanced via cation substitution of Gd3+

Abstract

Far-red (FR) light is involved in plant photomorphogenesis as a light signal. To realize the match between the absorption peak (730 nm) of a plant photosensitive pigment (Pfr) and the emission spectrum (708 nm) of a Y₃Ga_4.87O₁₂:0.13Cr³⁺ (YGO:0.13Cr³⁺) phosphor, in this study, we employed an ‘A site modification-B site response’ crystal-field-modulation strategy using the garnet structure Y₃Ga₅O₁₂, where doping large radius Gd³⁺ at the A site induced [YO₈] polyhedral expansion and triggered [GaO₆] octahedral distortion, thereby weakening the crystal field strength to achieve a red shift in the spectrum. The optimized Gd_1.2Y_1.8Ga_4.87O₁₂:0.13Cr³⁺ (GYGO:0.13Cr³⁺) phosphor exhibited high external quantum efficiency (34%) and excellent thermal stability (85.5% intensity at 423 K) under 450 nm excitation. Its emission peak at 726 nm was significantly close to 730 nm, while its luminescence intensity was improved by 141% that of the original system. It was successfully fabricated as an FR pc-LED device, achieving a 36.86 mW output power and 13.5% photoelectric efficiency at 100 mA current. Lettuce growth experiments showed that the device enhanced biomass production by 30% through precise spectral adaptation. The present work can promote the leap in plant lighting from rough supplementation to spectral customization through the whole chain of structural aberration–photoelectricity–biological effects.