Broadband UV-Excitation and Red/Far-Red Emission Materials for Plant Growth: Tunable Spectrum Conversion in Eu<sup>3+</sup>,Mn<sup>4+</sup> Co-doped LaAl<sub>0.7</sub>Ga<sub>0.3</sub>O<sub>3</sub> Phosphors
Fan Ding, Yiqing Zhou, Yue He, Yuanyuan Liang, Peilan Luo, Wenli Zhou, Jilin Zhang, Liping Yu, Zhongxian Qiu, Shixun Lian
Abstract
Broadband ultraviolet (UV) excitation and red/far-red emission phosphors can effectively convert solar spectrum to enhance photosynthesis and promote morphogenesis in plants. Based on the above application requirements, Eu 3+ single-doped LaAl 1– y Ga y O 3 solid solutions and Eu 3+,Mn 4+ codoped LaAl 0.7 Ga 0.3 O 3 phosphors were designed and synthesized in this work. The LaAl 0.7 Ga 0.3 O 3:0.05Eu 3+ (LAG:Eu 3+ ) phosphor exhibits a strong charge transfer band (CTB) excitation and characteristic 5 D 0 → 7 F 2 transition red emission (619 nm), which is very similar to the luminescence properties of Eu 3+ -organic ligand compound (EuL 3 ). Rietveld refinement studies further revealed that the cation substitution disturbs the site symmetry. The optimal Eu 3+, Mn 4+ co-doped LaAl 0.7 Ga 0.3 O 3 (LAG:Eu,Mn) phosphor possesses a dual-band excitation spectrum in broadband ultraviolet (UVA, UVB) area and a dual-band emission spectrum within red/far-red area. Under the sunlight radiation, the real-time spectrum of luminous laminated glasses fabricated by coating the LAG:Eu,Mn phosphor shows the percentage of radiant intensity in the red/far-red region significantly increases, suggesting that the phosphor can be a promising candidate for solar spectral conversion in plant cultivation. We believe this work provides a new idea for developing novel broadband ultraviolet excitation and red/far-red emission phosphors.