Synthesis and luminescence properties of deep-red-emitting LiAlSi2O6:Mn4+ for plant growth lighting

Abstract

Light can improve the growth and development of most plants, and the red/deep-red light in the 600–760 nm region is very good for phytochrome red and phytochrome far-red of plants, causing a great interest in the research and development of the deep-red-emitting luminescence materials. In this work, a pure phase LiAlSi₂O₆:Mn⁴⁺ with monoclinic crystal structure and only luminous center (Mn⁴⁺) is synthesized successfully in air. The excitation spectrum of LiAlSi₂O₆:Mn⁴⁺ covers the region from 220 to 550 nm owing to the O²⁻ - Mn⁴⁺ charge transfer and the ⁴A_2g → ⁴T_1g and ⁴T_2g transitions of Mn⁴⁺. We observe the deep-red emission of LiAlSi₂O₆:Mn⁴⁺ with emission peak at ∼663 nm in the range of 600–850 nm due to the transitions ²E_g → ⁴A_2g of Mn⁴⁺ and analyze the luminous mechanism. The optimal doping concentration of Mn⁴⁺ (0.1mol%) is determined by the concentration dependent emission spectra. We analyze the concentration quenching mechanism and investigate the lifetimes of LiAlSi₂O₆:Mn⁴⁺ with different Mn⁴⁺ concentration. The good thermal stability of LiAlSi₂O₆:Mn⁴⁺ is confirmed via the temperature dependent emission spectra. The potential applications of LiAlSi₂O₆:Mn⁴⁺ in plant growth LED lighting are estimated by comparison of spectral properties of LiAlSi₂O₆:Mn⁴⁺ and plant.