Photoelectrochemical Characterization of Novel Rhodium Iodide Photoconductors

Abstract

The physical and photoelectrochemical (PEC) properties of three rhodium iodide semiconducting materials have been investigated; crystalline , amorphous , and a new material that may be formulated as . Although the former two materials have been previously prepared, their semiconducting properties have not been examined. A previously unreported semiconducting material results from reacting with triiodide ion in aqueous solutions. Its chemical and physical properties are substantially different from the known rhodium iodides (either crystalline or amorphous). The new material has been isolated as a powder and spontaneously deposits onto substrates including conducting coated glass and freshly etched titanium metal. Chemical reactivity, ESCA, and PEC properties are reported for this new material. The new photoconductor is found to be p‐type with a bandgap of 1.17 eV (indirect) and a direct transition at 1.67 eV. Doping densities depend on the stoichiometry of the original solution phase reactants. The anisotropic photoresponse and the nonstoichiometry of are explained with a chain‐like structure of edge sharing octahedra found in . is photostable for the photoreduction of triiodide, protons, and ferricyanide in aqueous solutions at potentials positive of 0.0 V (vs. SCE).