Low‐dimensional organic–inorganic hybrid perovskites (OIHPs) with broadband emission attract immense scientific interest due to their potential application for the next generation of solid‐state lighting. However, due to low exciton utilization, organic cations generally adjust structure rather than contribute the band edge to affect optical properties. Based on this, OIHPs are usually allowed to obtain a low photoluminescence quantum yield (PLQY). Herein, a good charge transfer carrier (p‐phenylenediamine, PPDA) as organic cation is rationally employed and a novel indium‐based perovskite is synthesized. By coupling with H2O molecules, a strong interaction between organic and inorganic components is realized by hydrogen bonding, which has good transportability and greatly improves the exciton utilization. The regions of hydrogen bonding show high electron mobility, combined with the induced recombination center, improving the progress of charge relaxation. As a result, the regulation of hydrogen bond strength based on the microstructure optimization directly determines the optical emission intensity, realizing nearly 100% PLQY. Further, the polyhydrogen bond structure makes each component a stronger interaction, showing high stability in polar, organic, and acidic solvent, as well as long‐term storing, which represents one of the highest overall performances for lighting in OIHPs.

Luminescent materials have attracted considerable attention because of their extensive applications, for example, in lighting, display, and imaging. As one of the emerging luminescent materials, perovskites have been widely studied and reported. Among them, Pb-based perovskites have shown great promise as their photoluminescence quantum yield (PLQY) is almost 100%. However, the high chemical toxicity and low stability of Pb-based perovskites increase their production costs and limit their practical applications. Sn-based perovskites are also widely studied and their PLQY can reach approximately 90%; however, Sn 2+ easily oxidizes to Sn 4+ especially upon air exposure. When compared with Pband Sn-based perovskites, Sb-based perovskites have the advantages of low chemical toxicity and high thermal stability. Furthermore, the optical properties of Sb-based perovskites have been improved in recent years and are expected to surpass those of Pb-and Sn-based perovskites. Herein, we report a novel series of (4-HBA)SbX5•H2O single crystals (where 4-HBA is short for 4-hydroxybenzylamine, and X is Cl or Br). High quality single crystals of (4-HBA)SbBr5•H2O, (4-HBA)SbBr3Cl2•H2O, and (4-HBA)SbCl5•H2O with Sb 5+ can be prepared via the solvothermal method. The abovementioned three materials belong to the P-1 space group. The halide and hydroxyl ions surrounded by Sb 5+ ions in 4-hydroxybenzylamine formed distorted octahedral structures. Based on the results of steadystate fluorescence spectroscopy, excitation spectroscopy, transient fluorescence spectroscopy, fluorescence lifetime imaging, and density functional theory, it was found that the (4-HBA)SbBr5•H2O single crystal has a direct band gap, whereas the single crystals of (4-HBA)SbBr3Cl2•H2O and (4-HBA)SbCl5•H2O have an indirect band gap. When the concentration of Cl − in (4-HBA)SbX5•H2O increased, the band gap increased from 2.99 to 3.58 eV and the photoluminescence wavelength decreased from 618 to 595 nm. The obtained results also showed that the emission of the (4-HBA)SbX5•H2O single crystal originated from the self-trapping exciton effect. With the introduction of Cl − , the size of the [SbX5O] 2− octahedron decreased, the exciton shielding reduced, and the exciton absorption was enhanced. Additionally, after replacing Br − with Cl − , the radiation recombination process of the excited electrons from the Sb 5+ ions surrounding the halide ions gradually replaced the electron recombination of the hydroxyl ions, which extended the fluorescence lifetime from 12 to 22 ns and improved the PLQY by a factor of approximately 40.