Hydrolysis Reaction‐Induced Phase Regulation of Sb‐doped Zero‐Dimensional Perovskite Cs–In–Cl Nanocrystals for Optoelectronic and Information Encryption Applications

Abstract Phase‐controlled synthesis of all‐inorganic perovskite nanocrystals (NCs) has attracted extensive attention for optoelectronic applications. However, H₂O, often considered an unfavorable factor, has not been found to influence the resulting phase composition. Herein, the hydrolysis reaction‐induced phase regulation of 0D perovskite Cs–In–Cl: Sb NCs by manipulating the H₂O addition is reported. Specifically, Cs–In–Cl: Sb crystallizes as Cs₃InCl₆: Sb in the absence of H₂O addition. In contrast, the addition of H₂O triggers the hydrolysis of the injected chlorine source (phenylphosphonic dichloride, PhPOCl₂), resulting in an increased concentration of Cl⁻ ions and subsequently promoting the formation of Cs₄InCl₇: Sb NCs. Moreover, the hydrogen bonds formed between isopropanol (IPA) and H₂O/oleic acid (OA)/oleylamine (OAm) mitigate the immiscibility between the 1‐octadecene (ODE)/OA/OAm mixture and H₂O, which facilitates the passivation of OA/OAm on the Cs₄InCl₇: Sb NCs. Additionally, it is demonstrated that a reversible phase transition between Cs₄InCl₇: Sb and Cs₃InCl₆: Sb can be achieved by heating–cooling cycles. Furthermore, the application for white light‐emitting diodes, information encryption, and fluorescent composite films based on Cs₄InCl₇: Sb NCs is showcased. This work not only paves a new strategy to regulate the phase composition of perovskites but also introduces a novel fluorescent material of Cs₄InCl₇: Sb for multifunctional applications.