Intermolecular arrangement facilitated broadband blue emission in group-12 metal (Zn, Cd) hybrid halides and their applications

Various fluorescent organic materials are widely known for their potential applications in light-emitting diodes, organic lasers, anti-counterfeiting and bio-imaging. However, poor emission efficiency and stability issues limit their usability. Here we report the syntheses, crystal and electronic structures, and optical characterizations of two new hybrid organic-inorganic group 12 halides, (P-xd)ZnCl4 and (P-xd)CdCl4 (where (P-xd) = p-xylylenediammonium). Single crystals of both compounds can be conveniently synthesized by solution chemistry methods from their low-cost, low toxicity and easily available precursors. (P-xd)ZnCl4 possesses a crystal structure featuring alternating layers of organic cations and completely separated anionic [ZnCl4]2- tetrahedral units of zero-dimensional (0D) connectivity. In contrast, (P-xd)CdCl4 adopts similar layering of organic cations sandwiched between perovskite sheets of two-dimensional (2D) connectivity, which are formed by corner-sharing anionic [CdCl6]4- octahedral units. The structural, optical, and electronic studies suggest that the incorporation of organic and inorganic structural units into a hybrid structure improves its blue emission efficiency with nearly 23 times and 4 times higher photoluminescence quantum yield (PLQY) values in (P-xd)ZnCl4 and (P-xd)CdCl4, respectively, as compared to the organic precursor. Notably, PLQY of 23% for (P-xd)ZnCl4 is the highest reported to date for Zn-based hybrid organic-inorganic metal halides, where emission originates from the organic component. Both (P-xd)ZnCl4 and (P-xd)CdCl4 demonstrate considerably improved air-, thermal- and photostability, which suggest their suitability for potential practical applications such as fingerprint detection and solid-state lighting. The highly ordered intermolecular rearrangement due to the incorporation of group 12 metal (Zn and Cd) halides in p-xylylenediammonium resulted nearly 23 and 4 times higher emission efficiency in hybrid (P-xd)ZnCl4 and (P-xd)CdCl4 than that of the organic component. [Display omitted] •Crystal and electronic structures, and optical properties of two new hybrid Zn and Cd halides are reported.•Compounds are prepared using low-cost starting materials, and show improved air-, thermal- and photostability.•Highest reported PLQY among Zn-based hybrid materials where emission originates from the organic component.•Both hybrid metal halides demonstrate potential for practical applications.