Poster Session III: ENERGY RESEARCH AND APPLICATIONS (GERA)
Estimating the HOMO-LUMO levels of MoS2 and MoSe2 by Cyclic Voltammetry
Poster 412Photovoltaic devices are important for green energy production from the sun. One of the promising device structures is the bulk heterojunction (BHJ), which is useful for solar cells (SCs). The BHJ SCs involve layers of materials for generating and separating electron-hole pairs. To enable effective flow of electrons and holes, the HOMO-LUMO energy levels of these materials must be energetically compatible (HOMO: Highest Occupied Molecular Orbital, LUMO: Lowest unoccupied Molecular Orbital).
Here, we demonstrate a method to determine the HOMO-LUMO levels of nanoscale Transition Metal Dichalcogenides (TMDCs). Specifically, we synthesize quantum dots (QDs) of molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) with sizes <10nm, for the potential use as the active layers of BHJ SCs. To date, quantitative estimation of HOMO-LUMO levels of tiny nanoparticles is still challenging. We use cyclic voltammetry (CV) to estimate the reduction and oxidation (Redox) potential of MoS2 and MoSe2 QDs. Our experiments are performed in a three-electrode cell consisting of a working electrode, a platinum counter electrode, and Ag/AgCl reference electrode. The details of our synthesis method, characterization with atomic force microscopy (AFM), transmission electron microscopy (TEM), fluorescent and UV-Visible spectroscopy will be presented. Result on CV measurements and the calculation of the HOMO-LUMO energy levels will be discussed. We demonstrated the significance of precise HOMO-LUMO level measurements for advancing BHJ SCs