Artificial mimics of light-harvesting organic pigment via a double-perovskite structure (LiLa2SbO6:Bi3+, Mg2+, Mn4+) with single-composition and structure-activity relationship

Abstract

Green photosynthetic pigments play a major role in light-harvesting for biological substances and bio-mimetic strategy will provide a structural or functional model for natural antenna system. But the precise supramolecular structure of chlorosome has still not been clearly identified and the simulation of its function with new alternatives will be a real challenge. It has been well accepted that blue and far-red light are responsible for photosynthesis and photomorphogenesis in the process of plant growth. In this work, a series of single-composition LiLa2SbO6 (abbreviated as LLSO): xBi3+, yMg2+, zMn4+ phosphors with double perovskite‐type structure and the evaluation as blue and far-red dual-emission light for plant growth light-emitting diodes (LEDs) have been reported via a high-temperature solid-state reaction method. Under near ultraviolet-light (n-UV) excitation at 355 nm, intense blue emission (ranging from 360 to 500 nm, 3P1 → 1S0) from Bi3+ and far-red emission (650–750 nm, 2Eg → 4A2g) from Mn4+ are found in Bi3+-Mn4+ co-activated LLSO phosphors. To further optimize the photophysical properties, smaller Mg2+ has been incorporated into Li + site in Bi3+-doped LLSO phosphor to control blue emission of Bi3+. With the increase of Mg2+ content, an obvious red shift (~15 nm) of Bi3+ emission band has been detected in the blue region, which is almost overlapped with the absorbance of Chlorophyll-B (around 450 nm). Moreover, the photoluminescence (PL) emission intensity and decay lifetime of Bi3+ can be improved by substituting Mg2+ for Li+. These changes should be attributed to the combined effects of the crystal field splitting and the superior lattice rigidity. Finally, the temperature-dependent PL spectra of the composition-optimized phosphor are measured, and the excellent thermal-stable emission (up to 473 K) has been obtained. It has been observed that Bi3+ blue emission and Mn4+ far-red emission exhibit different temperature quenching effect and such phosphor can be considered as an ideal candidate in optical thermometry.