Organic Molecule-Induced Charge Exchange in MoS ₂ FETs: Experimental and Theoretical Insights

This work investigates charge exchange dynamics in MoS2 field-effect transistors (FETs) induced by organic molecule adsorption through both experimental and theoretical studies. Adsorption of various π-conjugated molecules such as copper phthalocyanine (CuPc), cobalt phthalocyanine (CoPc), phthalocyanine (H2Pc), and methylene blue (MB) on the MoS2 channel significantly modulates its electrical characteristics, resulting in distinctive changes in transfer curves (Id–Vg) and threshold voltages (Vth). These variations are consistent with the direction of charge transfer, as controlled by the relative energy levels of the molecular HOMO–LUMO gaps and band edges of MoS2. Electronic calculations based on density functional theory (DFT) confirm that electron-rich molecules act as electron acceptors, which display p-type behavior, and donor-type molecules allow n-type behavior. Theoretical calculation of bandgap and density of states analyses involving pristine and molecule-adsorbed MoS2 further supports interfacial interactions resulting in Fermi level tuning. These findings explain the molecular-level mechanisms governing charge modulation in MoS2-FETs, offering valuable insights for molecular sensing and nanoelectronic applications.