Solution-Synthesized In₄SnSe₄ Semiconductor Microwires with a Direct Band Gap

Semiconductor materials having direct band gaps that overlap well with the solar spectrum are important for a variety of applications in solar energy conversion and optoelectronics. Here, we identify the ternary chalcogenide In₄SnSe₄ as a direct band gap semiconductor having a band gap of approximately 1.6 eV. In₄SnSe₄, which contains isolated tetrahedral [SnIn₄]⁸⁺ clusters embedded in an In-Se framework, was synthesized by precipitation from solution at 300 °C. The In₄SnSe₄ product consists of microwires having lengths of approximately 5-20 μm and widths of approximately 100-400 nm. Band structure calculations predict a direct electronic band gap of approximately 2.0 eV. Diffuse reflectance UV-visible spectroscopy qualitatively validates the predicted direct band gap, yielding an observed optical band gap of 1.6 eV.