expected to exhibit intriguing optical properties. [22,23] This is because the coordinated metal octahedra are spatially isolated by surrounding inorganic or organic cations, resulting in strong exciton confinement and self-trapped exciton (STE) emission effects. The STE emission in 0D lead-free metal halides originates from the lattice deformation of metal halide structures and possesses some typical features, such as broadband PL emission and large Stokes shift. [24][25][26] Recently, a series of 0D lead-free metal halides have been reported to exhibit intriguing STE emissions. [27][28][29][30][31][32][33][34] 0D all-inorganic copper halides are one kind of enthralling materials due to their low toxicity and earth-abundant elements. In particular, Cu atoms are fourfold coordinated with halide ions to form tetrahedral structure, [35] which favors the Jahn-Teller distortion to produce strong STE emission. [36,37] Although the synthesis and optical properties of 0D Cs 3 Cu 2 I 5 NCs have been reported, [38] it is still challenging to prepare high-quality colloidal NCs of 0D all-inorganic copper(I) halides materials with isostructural series (such as Cs 3 Cu 2 X 5, X = I, Br, and Cl), and systematically investigate their halogen-dependent optical properties. Herein, we present the colloidal syntheses and optical characterizations of Cs 3 Cu 2 X 5 (X = I, Br, and Cl) NCs. These colloidal cesium cuprous halide NCs possess well-defined shapes, narrow size distributions, and tunable emissions. Intriguingly, with halogen ions changing from I − to Br − , and Cl − , Cs 3 Cu 2 X 5 NCs exhibit gradually redshifted emission peaks. Meanwhile, the high PL quantum yield (PLQY) of 48.7% is achieved on Cs 3 Cu 2 Cl 5 NCs, while Cs 3 Cu 2 I 5 NCs exhibit considerable air stability over 45 days.In our work, Cs 3 Cu 2 X 5 NCs were obtained via a hot injection method. [39,40] In particular, Cs 3 Cu 2 I 5 NCs were prepared based on a hot plate route in air. Typically, oleylammonium iodide (OLA-I) precursor was injected into 1-octadecene (ODE) solution containing cupric acetate, cesium carbonate and oleic acid (OA) (see details in supporting information, SI) to initiate the reaction. The OLA-I precursor not only offers iodine ion, but also reduces Cu(II) to Cu(I) cations. Subsequently, Cu + combines with Cs + and I − to form Cs 3 Cu 2 I 5 NCs stabilized by OA and OLA ligands. The feeding ratio of inorganic salt precursors and the amount of OA are revealed to play key roles in producing Cs 3 Cu 2 I 5 NCs with pure orthorhombic phase ( Figures S1 and S2, Supporting Information). Figure 1a presents a representative transmission electron microscopy (TEM) image of as-prepared Cs 3 Cu 2 I 5 NCs, 0D lead-free metal halide nanocrystals (NCs) are an emerging class of materials with intriguing optical properties. Herein, colloidal synthetic routes are presented for the production of 0D Cs 3 Cu 2 X 5 (X = I, Br, and Cl) NCs with orthorhombic structure and well-defined morphologies. All these Cs 3 Cu 2 X 5 NCs exhibit broadband blue-green photolum...

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 (Ph3S+)‐based 0D HMHs. Notably, integrated afterglow and STE emissions with adjustable intensities are obtained in (Ph3S)2Sn1−xTexCl6 (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 (Ph3S)2Zn1−xMnxCl4 (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.

Self‐trapped exciton (STE) emission in some metal halides has acquired great interest in recent years due to their broadband emission, large Stokes shift, and high photoluminescence quantum yield (PLQY). However, severe thermal quenching of STE emission is still a critical bottleneck that impedes their application in light‐emitting field. Herein, a novel zero‐dimensional hybrid metal halide, Sb3+‐doped (BTPP)2MnCl4 (BTPP = Benzyltriphenylphosphonium), is accordingly synthesized to address this issue. This compound exhibits excitation‐dependent dual emissions including STE emission of antimony chloride tetrahedron and 4T1‐6A1 transition of Mn2+ ions, resulting in a tunable emission color from green to orange. More importantly, the PL intensity of STE emission at 420 K in (BTPP)2MnCl4:2.0%Sb can maintain 72.5% of its ambient value, which is superior to current organic–inorganic hybrid metal halides. Temperature‐dependent and time‐resolved spectroscopy results suggest that the high thermal stability of STE emission originates from the efficient energy transfer from (BTPP)2MnCl4 host to antimony chloride tetrahedron, which promotes the formation of STEs. The white light‐emitting diode based on this (BTPP)2MnCl4:2.0%Sb phosphor exhibits high‐performance warm white light with a correlated color temperature of 4827 K and a color rendering index of 88.7, which demonstrates its potential in solid‐state lighting applications.