Effect of polyhedron deformation on the 5d energy level of Ce3+ in lanthanide aluminum perovskites

 Physical Chemistry Chemical Physics, January 2019, 21(5)

Graphical abstract: Effect of polyhedron deformation on the 5d energy level of Ce3+ in lanthanide aluminum perovskites

The crystal-field levels of Ce3+ in a series of lanthanide aluminum perovskites have been investigated with reference to polyhedron deformation. For each compound, the corresponding ideal cuboctahedron is derived through a least-square procedure. The virtual energy levels of Ce3+ in these ideal polyhedrons are then obtained considering both crystal-field splitting and spin–orbit coupling. From comparison to real levels, we have a clear understanding of how polyhedron deformation affects the energy levels of Ce3+ in the perovskites.

Effects of full-range Eu concentration on Sr2-2xEu2xSi5N8 phosphors: A deep-red emission and luminescent thermal quenching

Journal of Alloys and Compounds 770 (2019) 1069-1077

To fabricate white-light-emitting diodes (white LEDs) with high color-rendering index or full light spectrum emission, the discovery of more efficient deep-red emitting phosphor materials is essential. In this paper, we have synthesized a series of Sr2-2xEu2xSi5N8 (0 ≤ x ≤ 1) solid-solution compounds, and have systemically investigated effects of full-range Eu concentration on their luminescence. Their emission band maximum can be largely tuned from 610 to 725 nm by increasing Eu content. Reabsorption at low Eu2+ concentration while both the energy transfer and Stocks shift at high Eu2+ concentration account for this large spectral red-shift. Luminescent thermal quenching performance gets worse with Eu2+ concentration increasing. The compound with x = 0.15 possesses the best crystallinity and the highest luminescence intensity with the peak position around 660 nm, and still maintains 88.5% room-temperature intensity at 400 K, indicating that great potential for the application as a deep-red phosphor.

Double perovskite Cs2AgInCl6:Cr3+: broadband and near-infrared luminescent materials

Inorg. Chem. Front., 2019,6, 3621-3628

Searching for high performance and broader applications of inorganic halide perovskites has drawn extensive attention. In this work, a Cr3+-doped halide perovskite, Cs2AgInCl6:Cr3+, which exhibits broadband near-infrared (NIR) emission is first obtained via the traditional high temperature solid-state reaction. A broad emission band ranging from 850 to 1350 nm centered at 1010 nm with a full-width at half-maximum (FWHM) of 180 nm is assigned to the spin-allowed 4T2 → 4A2 transition of octahedrally coordinated Cr3+ ions in a very weak crystal-field environment. The excitation bands centered at 353, 565 and 800 nm can be attributed to the absorption of the Cs2AgInCl6 host, the Cr3+ d–d transitions of 4A2 → 4T1 and 4A2 → 4T2, respectively. Upon 760 nm excitation, the photoluminescence quantum yield (PLQY) of Cs2AgIn0.9Cl6:0.1Cr3+ is about ∼22.03%. Cs2AgInCl6:Cr3+ phosphors with such broadband NIR emission have potential in phosphor converted light emitting diodes (pc-LEDs) which have applications in bioimaging and biomonitoring.