WSe2 is an earth-abundant semiconductor of interest for application as a photovoltaic absorber due to its high absorption coefficient, phase stability, and a direct bandgap of 1.2-1.5 eV that matches well for optimum absorption by photovoltaic cells. The solvothermal preparation method eliminates the need for expensive high-vacuum fabrication steps but the formation of nanocrystalline WSe2 in solution has not been explored in detail. We report that the formation of WSe2, as characterized by Raman spectroscopy, x-ray diffraction (XRD), scanning electron microscopy, and inductively coupled plasma optical emission spectroscopy (ICP-OES), in a series of aromatic solvents is sensitive to reaction temperature and the electron donating/withdrawing nature of solvent molecule substituents. At temperatures of 155 oC and above, the reaction between W(CO)6 and elemental selenium in yields WSe2 after heating for several hours. Conducting the reaction at lower temperatures yields a material that has a Raman spectrum and XRD pattern consistent with trigonal crystalline selenium; however, ICP-OES confirms the presence of tungsten. The role of the solvent in reaction intermediate formation as linked to the favorability of WSe2 product generation will be discussed.

Thermal and electronic effects on the solvothermal formation of nanocrystalline WSe2 in aromatic solvents

249th National Meeting (2015)

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