A Halobismuthate Hybrid Characteristic of a T-Shaped Cation: Structure, Band Gap, Photocurrent Response, and Theoretical Study

Seeking new types of halobismuthate hybrids and exploring their physicochemical applications remain very attractive, yet full of challenges. Herein, we successfully fabricate and structurally characterize a novel halobismuthate with abundant weak interactions, namely, [MCP]₃Cs₂Bi₂I₆Cl₂ (<b>1</b>, HMCP⁺ = 1-methyl-4-(carboxyl)pyridinium), which features the discrete [BiI_5.45Cl_0.55]^3- anions that are charge-balanced by Cs⁺ ions and T-shaped [Bi(MCP)₃I_0.55Cl_1.45]⁺ cations. UV-vis diffuse reflection studies show that compound <b>1</b> possesses the semiconducting property, with an optical band gap of 2.35 eV. More prominently, it exhibits the excellent photoelectric switching ability, whose photocurrent density (2.64 μA·cm^-2) greatly outperforms or compares well with those of many high-performance metal halide analogues. In addition, compound <b>1</b> also displays wavelength-dependent photocurrent response behavior. Further theoretical analyses reveal that its valence band maximum and conduction band minimum are largely from the organic moiety and halogen, which may offer new guidance for the design and synthesis of newer halobismuthates with unique structures and desirable properties.