Metal halide perovskites (MHPs) have attracted extensive attention due to their excellent optoelectronic properties. Among them, layered two-dimensional (2D) metal halide materials with special structures have attracted extensive attention due to their superior stability and optoelectronic properties. Here, we report the 2D Ruddlesden−Popper (RP) phase Cs 3 Cd 2 Cl 7 synthesized by a solvothermal method, and the photoluminescence quantum yields (PLQYs) of the pristine Cs 3 Cd 2 Cl 7 sample (PLQY ∼ 10%) can be increased to 68 ± 5% through appropriate Sb 3+ doping. This should be the highest PLQY of all reported allinorganic RP-phase Cd-based perovskites so far. Our results indicate that the highly efficient cyan emission can be attributed to the common self-trapped exciton (STE) emission of the triplet states of Cd 2+ and Sb 3+ induced by strong electron−phonon coupling, and Sb 3+ :Cs 3 Cd 2 Cl 7 has excellent structural and spectral stability. This new material should be a promising candidate for optoelectronic applications in the future.

Organic–inorganic metal halides (OIMHs) have abundant optical properties and potential applications, such as light-emitting diodes, displays, solar cells, and photodetectors. Herein, we report zero-dimensional Mn-based OIMH (C8H20N)2MnCl4 single crystals synthesized by a simple slow evaporation method, which exhibit intense green emission at 520 nm originating from 4T1–6A1 transition of Mn2+ ions. Large organic cations in the crystal structure result in the isolated [MnCl4]2– tetrahedrons, and the closest Mn–Mn distance reaches 9.07 Å, which effectively inhibits the migration of excitation energy between adjacent Mn2+ emission centers, thus achieving a high quantum yield (∼87%) and a long photoluminescence (PL) lifetime (3.42 ms). The different optical and structural properties at low and high temperatures are revealed by temperature-dependent PL and X-ray diffraction spectra. The PL spectra and lifetimes under the heating and cooling processes indicate that the optical property transitions are reversible at 220/240 K. Our work provides a promising strategy for building multifunctional optoelectronic materials and insights into the understanding convertible photophysical properties from isomers of metal halides.

In recent years, low-dimensional lead-free metal halides have captured wide interest in the application of fluorescence anticounterfeiting due to their unique optical properties, low toxicity, and excellent environmental stability. Herein, we report an effective multimode photoluminescent material of Cu + @Sb 3+ -codoped Cs 2 ZnCl 4 microcrystals via a facile solution synthesis method. Upon a 365 nm ultraviolet (UV) excitation, Cu + @Sb 3+ -codoped Cs 2 ZnCl 4 shines a highly efficient broad red emission band at 714 nm. Under a 254 nm UV irradiation, this codoped compound exhibits a dual-band emission with an additional high-intensity emission band at 492 nm, enabling a bright sky-blue emission to be observed. The study of the photophysical mechanism reveals that the observed dualemission bands at 492 and 714 nm in this compound stem from the self-trapped exciton emission of [CuCl 4 ] 3− and [SbCl 4 ] − clusters, respectively. In addition, inspired by the obvious excitation-wavelength-dependent emission characteristics and excellent stabilities of Cu + @Sb 3+ -codoped Cs 2 ZnCl 4 , we successfully applied this compound to fluorescent anticounterfeiting and information encryption−decryption applications.