MoSe2 Nanosheets with Tuneable Optical Properties for Broadband Visible Light Photodetection.

Full exploitation of two-dimensional (2D) semiconducting MoSe₂, an exciting 2D transition-metal dichalcogenide, in optoelectronics is hampered because of dearth of scalable production methods. Here, a redox-mediated green route growth of ultrathin MoSe₂ nanosheets and nanocrystals is reported. At solvothermal condition, molybdenum acetate [(CH₃COO^–)₂Mo²⁺]₂ at (+II) oxidation state is employed as the molybdenum source for the first time to grow 2D MoSe₂ of 2H phase. Edible olive oil acts as a solvent as well as a ligand to block the growth in the Z direction, leading to the formation of 2D MoSe₂. The bottom-up solution-processed method differs distinctly from other available synthesis methods in terms of the 2D MoSe₂ nanosheet growth of the semiconducting phase (2H) without using any template or any external reducing agent. Evolution of MoSe₂ nanosheets is systematically studied by X-ray diffraction and Raman spectroscopy with the variation of the reaction temperature and the reaction time. Prolonged sonication and gradient centrifugations enable in obtaining MoSe₂ nanocrystals of different sizes. Tuneable optical properties and temperature-dependent emissions of MoSe₂ nanocrystals and nanosheets are studied by UV–visible and photoluminescence spectroscopies. Finally, we have fabricated a photoconductive device which shows broadband visible light detection, demonstrating the potential use of bottom-up solution-processed semiconducting MoSe₂ in broadband photodetection applications. [ABSTRACT FROM AUTHOR]