Dimensional Reduction of Cs2AgBiBr6: A 2D Hybrid Double Perovskite with Strong Polarization Sensitivity

By dimensional reduction of the 3D motif of Cs2AgBiBr6, a lead‐free 2D hybrid double perovskite, (i‐PA)2CsAgBiBr7 (1, i‐PA=isopentylammonium), was successfully designed. It adopts a quantum‐confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio αb/αc=1.9 at 405 nm). Such anisotropy attributes result in the strong polarization‐sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization‐sensitive materials. A lead‐free hybrid double perovskite, (i‐PA)2AgBiCsBr7, has been designed through dimensional reduction of the 3D prototype of Cs2AgBiBr6. Its unique quantum‐confined 2D bilayered motif results in the natural anisotropy of physical attributes, which accounts for its polarization‐sensitive response with large dichroic ratios.