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, H 2 O, 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 H 2 O addition is reported. Specifically, Cs–In–Cl: Sb crystallizes as Cs 3 InCl 6 : Sb in the absence of H 2 O addition. In contrast, the addition of H 2 O triggers the hydrolysis of the injected chlorine source (phenylphosphonic dichloride, PhPOCl 2 ), resulting in an increased concentration of Cl − ions and subsequently promoting the formation of Cs 4 InCl 7 : Sb NCs. Moreover, the hydrogen bonds formed between isopropanol (IPA) and H 2 O/oleic acid (OA)/oleylamine (OAm) mitigate the immiscibility between the 1‐octadecene (ODE)/OA/OAm mixture and H 2 O, which facilitates the passivation of OA/OAm on the Cs 4 InCl 7 : Sb NCs. Additionally, it is demonstrated that a reversible phase transition between Cs 4 InCl 7 : Sb and Cs 3 InCl 6 : Sb can be achieved by heating–cooling cycles. Furthermore, the application for white light‐emitting diodes, information encryption, and fluorescent composite films based on Cs 4 InCl 7 : 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 Cs 4 InCl 7 : Sb for multifunctional applications.