Search

All-inorganic lead-free luminescent metal halides have attracted considerable interest for their special optical properties in various optoelectronic applications. Among them, lanthanide-based Cs3LnCl6 metal halides, with low phonon energies and suitable crystallographic features, have been in the spotlight due to their appealing optical properties. However, it remains challenging for us to know how to simply and efficiently synthesize lanthanide-based Cs3LnCl6 metal halides, and how to optimize their low absorption and emission efficiencies owing to the parity-forbidden f–f transitions. In this minireview, we summarized several synthesis approaches towards both Cs3LnCl6 polycrystals and nanocrystals. The association of the crystal/electronic structure, optical properties and applications is discussed in three sections: self-trapped emission, down-conversion luminescence, and upconversion luminescence. We provide not only the synthesis strategies and recent progress in the luminescence properties of Cs3LnCl6, but also their promising future as alternatives to their toxic and poorly stable lead-based counterparts. [ABSTRACT FROM AUTHOR]

An ultrawide-color-gamut backlight is crucial for achieving ultrahigh definition and ultrahigh resolution liquid crystal displays (LCDs), where green-emitting phosphors with narrow spectral emission are the decisive factors. However, the key green-emitting phosphors currently used in light-emitting diode (LED) backlights, such as commercial β-SiAlON:Eu2+, have the disadvantages of a wide emission band and large particles. In order to display more colorful and vivid photographs, there is an urgent need to accelerate the development of narrow-band green-emitting phosphors with independent intellectual property rights and high quantum efficiency. This article outlines the design of green-emitting phosphors and the improvement of their luminescent properties. From a design perspective, an optimal phosphor must consider the host material and the activator. The emission bands of Tb3+, Mn2+, Ce3+ and Eu2+ are usually located in the visible region, and the short luminesence decay time of Eu2+/Ce3+ makes it a potential activator for high-quality displays. In the exploration and selection of hosts for novel phosphors, approaches such as single-particle diagnosis, high-throughput density functional theory (DFT) calculations and mineral-inspired prototype evolution are commonly employed. Thermal stability and quantum efficiency (QE) are critical properties for phosphors, and various strategies to enhance these characteristics are discussed herein. Moreover, the color gamuts of various green-emitting phosphors are presented, highlighting their applications in green-emitting phosphor-based WLEDs used in LCD screens and projectors. These WLEDs display more vivid image quality than the conventional commercial WLEDs. Finally, the future outlook on exploring and developing green-emitting phosphors with enhanced performance is discussed. [ABSTRACT FROM AUTHOR]

Mn 2+ -doped luminescent materials play a significant role in a variety of fields, including modern lighting, displays, and imaging. Mn 2+ exhibits a broad and adjustable emission, hinging on the local environment of the crystal field and the interaction of the 3d 5 electrons. However, it is still a challenge to realize the precise control of the emission of Mn 2+ ions due to site-prior occupation in a specific lattice. Here, the formation of Mn-Mn dimers is proposed to be an effective strategy to design a novel red emission. Multimode emitters in Mn 2+ -activated AZn 4 (PO 4 ) 3 (A = K, Rb, and Cs) with unique [Zn 4 PO 12 ] chains and [ZnO n ] groups are observed to achieve regular green and unusual red emissions. KZn 4 (PO 4 ) 3 :Mn 2+ shows broad dual emissions at 542 and 608 nm, attributed to [MnO 4 ] and [Mn 2 O 7 ] dimers, respectively. While K is replaced with Rb and Cs, the Zn ions form [ZnO 4 ] tetrahedra and [ZnO 5 ] octahedra. RbZn 4 (PO 4 ) 3 :Mn 2+ exhibits a broad red emission at 618 nm, ascribing to [Mn 2 O 7 ] and [Mn 2 O 8 ] dimers. CsZn 4 (PO 4 ) 3 :Mn 2+ also displays a broad orange-red emission at 608-620 nm with increasing doping levels, deriving from energy transfer from [MnO 5 ] to [Mn 2 O 7 ] and [Mn 2 O 8 ] dimers. This work provides a framework for creating novel red emissions from Mn 2+ -doped luminescent materials.

Erbium ions are commonly used to extend the photoelectric properties of metal halide perovskites from visible to near-infrared range. However, achieving high-efficiency multimode luminescence in a single system is difficult due to the weak absorption associated with forbidden 4f-4f transitions. In this study, a unique strategy is proposed to adjust multimode luminescence and enhance the second near-infrared region (NIR-II) emission in Cs 2 NaBiCl 6 by incorporating Fe 3+ ions. The as-prepared material demonstrates reversible thermochromism, driven by strong electron-phonon coupling effect, and exhibits tunable luminescence that can be adjusted by altering excitation energy and temperature. Notably, benefitting from the charge transfer transition of Fe 3+ -Cl - along with the influence of Fe 3+ doping on the geometrical and electronic structures, the blue-excitable (450 nm) NIR-II emission around 1541 nm from Er 3+ is realized for the first time, achieving an intensity 16.7 times higher and a maximum photoluminescence quantum yield (PLQY) of 22.5 %. This enhancement enables innovative applications such as two-dimensional information encryption by the multi-channel cooperative responses and improved NIR imaging. The study highlights the potential of Fe 3+ doping in optimizing absorption and multimode luminescence in perovskites, opening avenues for advanced applications in blue-excitable NIR light emitting diodes (LEDs), thermometer, anti-counterfeiting, and NIR imaging., (© 2024 Wiley-VCH GmbH.)