Vacancy Effect on the Luminescent and Water Responsive Properties of Vacancy‐Ordered Double Perovskite Derivatives

Abstract Vacancy‐ordered perovskites and derivatives represent an important subclass of hybrid metal halides with promise in applications including light emitting devices and photovoltaics. Understanding the vacancy‐property relationship is crucial for designing related task‐specific materials, yet research in this field remains sporadic. For the first time, we use the Connolly surface to quantitatively calculate the volume of vacancy ( V □, □=vacancy) in vacancy‐ordered double perovskite derivatives (VDPDs). A relationship between void fraction and the structure, photoluminescent properties and humidity stability was established based on zero‐dimensional (0‐D) [N(alkyl) 4 ] 2 Sb□Cl 5 □′‐type VDPDs. Compared with the more commonly studied A 2 M (IV) X 6 □‐type double perovskite ( A =cation, M =metal ion, X =halide), [N(alkyl) 4 ] 2 Sb□Cl 5 □′ features double vacancy sites. Our results demonstrate an inverse relationship between the photoluminescent quantum yield and V □ in 0‐D VDPDs. Additionally, structural transformation from A 2 SbCl 5 to A 3 Sb 2 Cl 9 was first reported, during which the novel ‘gate‐opening’ gas adsorption phenomenon was observed in VDPDs for the first time, as evidenced by ‘ S ’‐shaped sorption isotherms for water vapor, indicating a cation‐controlled water‐vapor response behavior. A mixed‐cation strategy was developed to modulate the humidity stability of VDPDs. Characterized by controllable water‐responsive behavior and unique ‘ on ‐ off ‐ on ’ luminescent switching, A 2 M (III)□ X 5 □′‐type materials show great promise for multi‐level information anti‐counterfeiting applications.