Enhanced near-infrared emission for plant growth and night vision through strong energy transfer in BaLu2SiAl4O12: Ce3+, Cr3+

Abstract

Phytochrome Pr and Pfr are essential for plant growth and photosynthesis, primarily absorbing deep red light at 660 nm and near-infrared (NIR) light at 730 nm. This paper is dedicated to enhance the efficiency of deep red to NIR light emission in BaLu_2–xSiAl_4–yO₁₂ (BLSA): xCe³⁺, yCr³⁺ through an energy transfer strategy designed to promote plant growth and improve night vision. It is found that sample doped solely with Cr³⁺ can emit deep red to NIR emission in BLSA; however, the spin-forbidden nature of the Cr³⁺ 3d→3d transition leads to low luminescence efficiency. On the contrary, in Ce³⁺-doped BLSA, Ce³⁺ ions efficiently absorb blue light and emit intense green light, which overlaps the absorption of Cr³⁺ ions in BLSA. This spectral overlap promotes the energy transfer from Ce³⁺ to Cr³⁺, thereby enhancing the deep red to NIR emission of Cr³⁺. This enhancement is evidenced by the external quantum efficiency of Cr³⁺ emission, which is 12.5% in the sample doped solely with Cr³⁺ and is increased to 48.6% when co-doped with Ce³⁺ ions. The energy transfer mechanism between Ce³⁺ and Cr³⁺ is found to primarily involve dipole–dipole interactions, as confirmed by Dexter's formula and multipole interaction modeling. In addition, by using BLSA:0.1Ce³⁺,0.03Cr³⁺ phosphor to fabricate NIR lighting devices, it is found that the emission spectra highly match the absorption spectra of the phytochromes Pr and Pfr, demonstrating its great potential for application in indoor plant growth lighting. Moreover, the lighting source system is adaptable for various scenarios such as night vision and non-invasive bio-imaging, showcasing its promising versatility for application.