Dipole-Orientation-Dependent Förster Resonance Energy Transfer from Aromatic Head Groups to MnBr42- Blocks in Organic-Inorganic Hybrids

Pseudo-2D Layered Organic-Inorganic Manganese Bromide with a Near-Unity Photoluminescence Quantum Yield for White Light-Emitting Diode and X-Ray Scintillator

Eco-friendly lead-free organic-inorganic manganese halides (OIMHs) have attracted considerable attention in various optoelectronic applications because of their superior optical properties and flexible solution processibility. Herein, we report a novel pseudo-2D layered OIMH (MTP)2 MnBr4 (MTP: methyltriphenylphosphonium), which exhibits intense green emission under UV/blue or X-ray excitation, with a near-unity photoluminescence quantum yield, high resistance to thermal quenching (I150 °C =84.1 %) and good photochemical stability. These features enable (MTP)2 MnBr4 as an efficient green phosphor for blue-converted white light-emitting diodes, demonstrating a commercial-level luminous efficiency of 101 lm W-1 and a wide color gamut of 116 % NTSC. Moreover, these (MTP)2 MnBr4 crystals showcase outstanding X-ray scintillation properties, delivering a light yield of 67000 photon MeV-1 , a detection limit of 82.4 nGy s-1 , and a competitive spatial resolution of 6.2 lp mm-1 for X-ray imaging. This work presents a new avenue for the exploration of eco-friendly luminescent OIMHs towards multifunctional light-emitting applications.

Satellite Red Emission from a Single Green-Emissive MnBr42- Tetrahedron in Soft Hybrid Single Crystals

Photoinduced self-trapped exciton emission is common in soft matter metal halide semiconductors, whereas analogous phenomena in metal halide insulators with localized emitting centers and delayed satellite emission have rarely been identified. In this study, a new zero-dimensional Mn(II) hybrid of [3DPTPP]MnBr4 (3DPTPP = (3-(dimethylamino)propyl)(triphenyl)phosphonium) with only one crystallographic Mn2+ site but dual emission is reported. The delayed red emission (∼630 nm) is successfully assigned to a satellite of the green-emissive (∼530 nm) MnBr42- tetrahedron shifted by N-H vibration (∼2500 cm-1), directly evidenced by the Raman spectra and further supported by density functional theory calculation. The photoluminescence decay curves demonstrate their same origin, but the red emission exhibits a delayed process. The temperature- and pressure-dependent PL spectra, temperature-dependent distortion of the MnBr42- tetrahedron, and light polarization spectra confirmed the consistency and distinctness of the dual emission. This study will inspire further research on self-trapped optoelectronic processes in soft metal halides.

Formation mechanisms of CsPbBr3/Cs4PbBr6 microscale composites assisted with imidazolium cations and their device applications

The instability of all-inorganic perovskite nanocrystals (NCs) remains a major challenge to their practical applications in displays and lighting. In order to improve their environmental resistance, highly luminescent CsPbBr₃ NC embedded Cs₄PbBr₆ microcrystals (MCs) have been fabricated by an anti-solvent reprecipitation method with the assistance of 1-alkyl-3-methyl-imidazolium bromides. The heterostructure of the MCs is investigated in detail, and their formation mechanism is discussed in terms of the dissolution-precipitation equilibria and the total energy of variously scaled nanoparticles via density functional theory (DFT) calculations. Although the imidazolium ligands are not directly capping with the inner CsPbBr₃ NCs, they are important to the formation of these MCs. The MCs exhibit better thermal resistance compared to conventional CsPbBr₃ NCs prepared by the hot-injection method. Additionally, a prototype white light-emitting diode (WLED) was fabricated to demonstrate its practical application prospects. Thanks to the narrow emission bands and enhanced stability of the MCs, the WLED shows greater performance compared to bare perovskite NCs, indicating its great potential as a green phosphor in lighting and display applications.

Integrated Afterglow and Self-Trapped Exciton Emissions in Hybrid Metal Halides for Anti-Counterfeiting Applications

0D hybrid metal halides (0D HMHs) are considered to be promising luminescent emitters. 0D HMHs commonly exhibit self-trapped exciton (STE) emissions originating from the inorganic metal halide anion units. Exploring and utilizing the emission features of the organic cation units in 0D HMHs is highly desired to enrich their optical properties as multifunctional luminescent materials. Here, tunable emissions from organic and inorganic units are successfully achieved in triphenylsulfonium (Ph₃ S⁺ )-based 0D HMHs. Notably, integrated afterglow and STE emissions with adjustable intensities are obtained in (Ph₃ S)₂ Sn_{1- x} Te_x Cl₆ (x = 0-1) via the delicate combination of [SnCl₆ ]^2- and [TeCl₆ ]^2- . Moreover, such a strategy can be readily extended to develop other HMH materials with intriguing optical properties. As a demonstration, 0D (Ph₃ S)₂ Zn_{1- x} Mn_x Cl₄ (x = 0-1) are constructed to achieve integrated afterglow and Mn²⁺ d-d emissions with high efficiency. Consequently, these novel 0D HMHs with colorful afterglow and STE emissions are applied in multiple anti-counterfeiting applications.

Controlled Modulation of the Structure and Luminescence Properties of Zero-Dimensional Manganese Halide Hybrids through Structure-Directing Metal-Ion (Cd2+ and Zn2+) Centers

Zero-dimensional (0D) metal halide hybrids with high exciton binding energy are excellent materials for lighting applications. Controlling/modulating the structure of the constituent metal halide units allows tunability of their photoluminescence properties. 0D manganese halide hybrids are currently attracting research efforts in lighting applications due to their eco-friendly and strong emission. However, structural transformation-induced tunability of their photophysical properties has rarely been reported. Herein, we demonstrate a rational synthetic strategy to modulate the structure and luminescence properties of 0D Mn(II) halide hybrids utilizing the structure-directing d¹⁰ metal ions (Cd²⁺/Zn²⁺). 0D metal halide hybrids of Cd²⁺/Zn²⁺, which act as hosts with tunable structures, accept Mn²⁺ ions as substitutional dopants. This structural flexibility of the host d¹⁰ metal ions is realized by optimizing the metal-to-ligand ratio (Cd/AEPip). This reaction parameter allows structural transformation from an octahedral (AEPipCdMnBrO_h) to a tetrahedral (AEPipCdMnBrT_d) 0D Mn halide hybrid with tunable luminescence (orange → green) with high photoluminescence quantum yield. Interestingly, when Zn²⁺ is utilized, a tetrahedral AEPipZnMnBr structure forms exclusively with strong green emission. Optical and single-crystal X-ray diffraction structural analysis of the host and the doped system supports our experimental data and confirms the structure-directing role played by Cd²⁺/Zn²⁺ centers. This work demonstrates a rational strategy to modulate the structure/luminescence properties of 0D Mn(II) halide hybrids, which can further be implemented for other 0D metal halide hybrids.

Unveiling White Light Emission of a One-Dimensional Cu(I)-Based Organometallic Halide toward Single-Phase Light-Emitting Diode Applications

Luminescent organometallic halide crystals, especially with single-component white emission, are urgently needed for light-emitting diode (LED) applications. Barriers for the applications, however, lie in their lead toxicity, poor stability, and low photoluminescence quantum yield (PLQY). Here, a one-dimensional Cu(I)-based hybrid metal halide (C₁₂H₂₄O₆)CsCu₂Br₃ is designed and prepared via a simple solution method. Upon 365 nm excitation, a broad-band white light emission centered at 535 nm with a full width at half maximum of 186 nm and a PLQY of 78.3% is monitored. The experimental results together with calculation data indicate that the existence of the split peaks at 486 and 570 nm at a low temperature is attributed to the decrease of energy level degeneracy by virtue of the lattice distortion. Moreover, the stability along with the good device performance of the as-fabricated white LED was also discussed. The results demonstrate that (C₁₂H₂₄O₆)CsCu₂Br₃ is highly competitive in lighting application, and it can further enable breakthrough material design for new luminescent organometallic halides.