Tunable Electronic and Optoelectronic Properties of MoS2 Through Molecular Coverage-Controlled Polyoxometalate Doping

We investigated the functionalization of pristine and post-deposition-annealed atomic layer deposition (ALD)-grown MoS2 films on silicon wafers with the polyoxometalate (POM) (nBu4N)3[HV12O32Cl(DyPc)] (referred to as V12-DyPc) and its impact on the optical and electronic properties of 2D semiconductor layers. Thin-film analysis confirms the formation of high-quality, polycrystalline MoS2 after annealing. The deposition of V12-DyPc induces a concentration-dependent reduction in A exciton emission and the emergence of negatively charged trion (A–) photoluminescence (PL), evidencing systematic charge transfer. Studies on thinner MoS2 layers grown by metal-organic chemical vapor deposition (MOCVD) corroborate this effect. Short-range surface ordering of POMs is detected on pristine, amorphous MoS2. Notably, V12-DyPc exhibits identical multilevel switching behavior on both amorphous and polycrystalline, annealed MoS2. On MoS2, V12-DyPc shows a significantly reduced lateral electronic density distribution (3 nm compared to 7 nm on highly oriented pyrolytic graphite (HOPG)) and a more positive first reduction potential (3.1 V vs. 2.1 V, respectively). These changes are due to the substantially increased surface roughness of MoS2 relative to the atomically flat HOPG substrate, and to the impact of a modified chemical environment on MoS2. Density functional theory (DFT) and molecular mechanics simulations reveal face-on bonding geometries, altered redox energetics, and substrate-dependent shifts in electronic states.