Zero-dimensional (0D) organic metal halides have captured extensive attention for their various structures and distinguished optical characteristics. However, achieving efficient emission through rational crystal structure design remains a great challenge, and how the crystal structure affects the photophysical properties of 0D metal halides is currently unclear. Herein, a rational crystal structure regulation strategy in 0D Sb­(III)-based metal halides is proposed to realize near-unity photoluminescence quantum yield (PLQY). Specifically, two 0D organic Sb­(III)-based compounds with different coordination configurations, namely, (C25H22P)2SbCl5 and (C25H22P)­SbCl4 (C25H22P+ = benzyltriphenylphosphonium), were successfully obtained by precisely controlling the ratio of the initial raw materials. (C25H22P)2SbCl5 adopts an octahedral coordination geometry and shows highly efficient broadband yellow emission with a PLQY of 98.6%, while (C25H22P)­SbCl4 exhibits a seesaw-shaped [SbCl4]− cluster and does not emit light under photoexcitation. Theoretical calculations reveal that, by rationally controlling the coordination structure, the indirect bandgap of (C25H22P)­SbCl4 can be converted to the direct bandgap of (C25H22P)2SbCl5, thus ultimately boosting the emission intensity. Together with efficient emission and outstanding stability of (C25H22P)2SbCl5, a high-performance white-light emitting diode (WLED) with a high luminous efficiency of 31.2 lm W–1 is demonstrated. Our findings provide a novel strategy to regulate the coordination structure of the crystals, so as to rationally optimize the luminescence properties of organic metal halides.

lead-free double perovskites of Cs 2 M(I) M(III)X 6 have drawn extensive attention and are seen as a promising alternative for LHPs. [3] The double perovskites are characterized by a 3D framework of alternating and corner-shared M(I)X 6 and M(III)X 6 octahedra. Particularly, although a great variety of double perovskites have been reported, only a few of them, such as Cs 2 NaInCl 6 , Cs 2 KInCl 6 , Cs 2 AgSbCl 6 , and Cs 2 AgBiBr 6 , have fascinating photoelectric characteristics. [4] Nevertheless, the double perovskites generally exhibit an unsatisfying photoluminescence efficiency, which is caused by their indirect bandgap characteristics or parity-forbidden transition in the direct bandgap system. [5] Hence, it is a great challenge to obtain double perovskites with highly efficient emission.Metal ion doping has been demonstrated to be a robust strategy to regulate the optical properties of LHPs, and has also achieved impressive results in double perovskites. For example, Sb 3+ doped Cs 2 NaInCl 6 shows a blue emission with a PLQY of 75.89%, [6] Sb 3+ doped Cs 2 KInCl 6 emits a cyan emission with a PLQY of 99.2%, [7] Bi 3+ doped Cs 2 (Ag 0.6 Na 0.4 )InCl 6 shines white emission with a PLQY of 86%, [8] Mn 2+ doped Cs 2 Na 0.2 Ag 0.8 InCl 6 shows a red emission with a PLQY of 32%. [9] Although single-doping technology of double perovskites can achieve efficient emission in the visible light range and has made significant progress in solid-state lighting (SSL), its further development is undoubtedly limited by its un-tunable emission and single scope of application. Recent works have suggested that co-doping strategy can provide multiple emission centers in a single compound, which endows double perovskites to have abundant optical properties, and can further develop its applications in multifunctional materials. For instance, Bi 3+ /Sb 3+ co-doped Cs 2 Ag 0.1 Na 0.9 InCl 6 exhibits a distinct excitation-wavelength dependent emission characteristic, which makes it show great potential in optical anti-counterfeiting. [10] More particularly, ns 2 metal ions (M 3+ = Bi 3+ and Sb 3+ ) can work as a sensitizer of Ln 3+ (Ln = Yb, Er, Nd), and construct an appropriate energy-transfer channel from ns 2 electrons to Ln 3+ , thus ultimately boosting the nearinfrared emission (NIR) of Ln 3+ . [11] Typical examples are that the NIR emission intensity of Bi 3+ /Er 3+ and Bi 3+ /Yb 3+ co-doped Cs 2 AgInCl 6 is about 45 and 27 times higher than that of single Recently, ns 2 metal ions (such as Bi 3+ and Sb 3+ ) doped double perovskites have captured intense attention for their efficient emission, however, achieving efficient and tunable white light emission is always an enormous challenge. Herein, Sb 3+ /Ho 3+ co-doped Cs 2 KInCl 6 double perovskites are proposed, and the photoluminescence results show that there are two emission bands, one broad cyan emission band stems from self-trapped exciton (STE) in [SbCl 6 ] 3octahedron, while another red emission band derives from the f-f transitions of Ho 3+ . The emission processes ...

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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.