MoSe<sub>2</sub> Nanosheets with Tuneable Optical Properties for Broadband Visible Light Photodetection
Arup Ghorai, S. K. Ray, Anupam Midya
Abstract
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.