Zero-Dimensional Hybrid Indium Halides with Efficient and Tunable White-Light Emissions

Phase Transition and Luminescent Property Change Induced by Different Organic Cations in One-Dimensional Double Perovskites

Double perovskites (DPs) have attracted attention in the field of luminescence due to their inherent broadband emission of self-trapping excitons. In this work, we choose [(CH3)3NCH2CHCH2]+ and [CH3CHOHCH2NH2]+ as organic cations to synthesize two new organic-inorganic hybrid DPs, [(CH3)3NCH2CHCH2]2KInCl6 (1) and [CH3CHOHCH2NH2]2KInCl6 (2). The [KCl6]3- and [InCl6]3- octahedra are interchangeably connected by sharing two opposite faces, forming a one-dimensional coordination chain. Each K atom coordinates with six chlorine atoms in 1, while it coordinates with two oxygen atoms in addition to the six chlorine atoms in 2. The coordination between ions K and O in compound 2 may have significantly reduced its luminescence. As a result, compound 1 shows bright-yellow light with a quantum yield of more than 90%, while 2 shows weak blue light with a quantum yield of only 0.98%. In addition, different from no phase transition found in 2, 1 undergoes a reversible phase transition at 324/307 K in the heating-cooling cycle. Through structural and spectral analysis and density functional theory calculation, we conclude that the larger degree of [InCl6]3- octahedral distortion and the larger anion distance (In···In) also cause the PLQY of compound 1 to be higher than that of compound 2.

Boosting Blue Self-Trapped Exciton Emission in All-Inorganic Zero-Dimensional Metal Halide Cs2ZnCl4 via Zirconium (IV) Doping

Low-dimensional metal halides with efficient luminescence properties have received widespread attention recently. However, nontoxic and stable low-dimensional metal halides with efficient blue emission are rarely reported. We used a solvothermal synthesis method to synthesize tetravalent zirconium ion-doped all-inorganic zero-dimensional Cs2ZnCl4 for the first time. Bright blue emission in the range of 370 nm-700 nm with a emission maximum at 456 nm was observed in Zr4+:Cs2ZnCl4 accompanied by a large Stokes shift, which was due to self-trapped excitons (STEs) caused by the lattice vibrations of the twisted structure. Simultaneously, the PLQY of Zr4+:Cs2ZnCl4 achieve an impressive 89.67%, positioning it as a compelling contender for future applications in blue-light technology.

Multiple Stimuli-Responsive Luminescent Chiral Hybrid Antimony Chlorides for Anti-Counterfeiting and Encryption Applications

Stimuli-responsive circularly polarized luminescence (CPL) materials are ideal for information anti-countering applications, but the best-performing materials have not yet been identified. This work presents enantiomorphic hybrid antimony halides R-(C5 H12 NO)2 SbCl5 (1) and S-(C5 H12 NO)2 SbCl5 (2) showing mirror-imaged CPL activity with a dissymmetry factor of 1.2×10-3 . Interestingly, the DMF-induced structural transformation is realized to obtain non-emissive R-(C5 H12 NO)2 SbCl5  ⋅ DMF (3) and S-(C5 H12 NO)2 SbCl5  ⋅ DMF (4) upon exposure to DMF vapor. The transformation process is reversed upon heating. DFT calculations showed that the DMF-induced-quenched-luminescence is attributed to the intersection of the ground and excited state curves on the configuration coordinates. Unexpectedly, the nanocrystals of the chiral antimony halides 1 and 2 were prepared and indicate the excellent solution process performance. The reversible PL and CPL switching gives the system applications in information technology, anti-counterfeiting, encryption-decryption, and logic gates.

High-Efficiency Intrinsic Yellow-Orange Emission in Hybrid Indium Bromide with Double Octahedral Configuration

Zero-dimensional (0D) In-based organic-inorganic metal halides (OIMHs) have received growing interest in recent years as promising luminescent materials. However, the high efficiencies of 0D In-based OIMHs are all dependent on Sb doping in the existing literature. Here, we report a novel 0D In-based OIMH (C₁₀H₂₂N₂)₂In₂Br₁₀, which exhibits intrinsic broadband emission (610 nm), and the photoluminescence quantum yield (PLQY) can reach 70% without Sb doping. (C₁₀H₂₂N₂)₂In₂Br₁₀ shows a typical 0D structure with three different In-Br polyhedra (two octahedra and one tetrahedron) separated by large organic cations. Based on the optical property measurements and theoretical calculations, we demonstrate that (C₁₀H₂₂N₂)₂In₂Br₁₀ is an indirect semiconductor with a band gap of 3.74 eV, and the In-Br inorganic moiety is primarily responsible for the intense emission of (C₁₀H₂₂N₂)₂In₂Br₁₀. Interestingly, the unique double octahedral configuration in (C₁₀H₂₂N₂)₂In₂Br₁₀ may enhance the structural distortion and stimulate the self-trapped excitons (STEs), leading to the related high PLQY. Our work provides a novel 0D In-based OIMH with high-efficiency intrinsic emission, which is helpful for understanding the structure-PL relationships of hybrid halides.

Reversible Luminescent Switching Induced by Heat/Water Treatment in a Zero-Dimensional Hybrid Antimony(Ⅲ) Chloride

Recently zero-dimensional (0-D) inorganic-organic metal halides (IOMHs) have become a promising class of optoelectronic materials. Herein, we report a new photoluminescent (PL) 0-D antimony(III)-based IOMH single crystal, namely [H₂BPZ][SbCl₅]·H₂O (BPZ = benzylpiperazine). Photophysical characterizations indicate that [H₂BPZ][SbCl₅]·H₂O exhibits singlet/triplet dual-band emission. Density functional theory (DFT) calculations suggest that [H₂BPZ][SbCl₅]·H₂O has the large energy difference between singlet and triplet states, which might induce the dual emission in this compound. Temperature-dependent PL spectra analyses suggest the soft lattice and strong electron-phonon coupling in this compound. Thermogravimetric analysis shows that the water molecules in the lattice of the title crystal could be removed by thermal treatment, giving rise to a dehydrated phase of [H₂BPZ][SbCl₅]. Interestingly, such structural transformation is accompanied by a reversible PL emission transition between red light (630 nm, dehydrated phase) and yellow light (595 nm, water-containing phase). When being exposed to an environment with 77% relative humidity, the emission color of the dehydrated phase was able to change from red to yellow within 20 s, and the red emission could be restored after reheating. The red to yellow emission switching could be achieved in acetone with water concentration as low as 0.2 vol%. The reversible PL transition phenomenon makes [H₂BPZ][SbCl₅]·H₂O a potential material for luminescent water-sensing.

Lead-free broadband orange-emitting zero-dimensional Sb3+-doped indium-based organic–inorganic metal halides

An orange-yellow phosphor Sb3+: (CH3NH3)4InCl6·Cl was prepared via a mechanical ball-milling method. Sb3+-doped (CH3NH3)4InCl6·Cl was able to emit orange light (∼607 nm) under UV light excitation, and the PLQY is as high as 67.72%.