(3-Methylbenzo[d]thiazol-3-ium)₂Cu₃I₅: A Copper Iodide Hybrid Photoconductor Assembled via Coulomb Interaction

Transition-metal copper acts as a potential alternative for toxicity lead in exploring hypotoxicity organometal halide semiconductors (OHSs), due to its cost-effectiveness, low toxicity, earth-abundance, and near-infrared absorption. However, the known Cu-OHSs not only are limited but also exhibit unsatisfactory optoelectronic performances. Herein, we report a novel Cu-OHS (3-methylbenzo[d]thiazol-3-ium)2Cu3I5 (denoted as Mebti-Cu3I5) constructed by one-dimensional (Cu3I5)2– anionic chains charge compensated by alkylated benzothiazole counterions. The (Cu3I5)2– represents a rarely reported chainlike structure formed by the edge sharing of (CuI4) tetrahedrons and (CuI3) plane triangles. The organic countercation Mebti with a dangling methyl on the N donor precludes the formation of a coordination bond, strong hydrogen bond, and halogen bond, which further endows Mebti-Cu3I5 a rare example that is assembled mainly by Coulomb interaction between inorganic and organic moieties. Mebti-Cu3I5 exhibits a direct band gap value of 2.40 eV with broadband absorption in the UV and visible light region. The photoconductive film device of Mebti-Cu3I5 fabricated by a recrystallization method shows good conductivity and high photoresponse, implying its potential application in a hypotoxicity photodetector. Density functional theory calculations were performed to unveil the band structure and the photoresponse mechanism.