We report a method to neutralize the mid-gap defect states in MoS2 monolayers using laser soaking of an organic/transition metal oxide (TMO) blend thin film. The treated MoS2 monolayer shows negligible emission from defect states as compared to the as-exfoliated MoS2, accompanied by a photoluminescence quantum yield improvement from 0.018 to 4.5% at excitation power densities of 10 W/cm2. The effectiveness of the method toward defect neutralization is governed by the polaron pair generated at the organic/TMO interface, the diffusion of free electrons, and the subsequent formation of TMO radicals at the MoS2 monolayer. The treated monolayers are stable in air, vacuum, and acetone environments, potentially enabling the fabrication of defect-free optoelectronic devices based on 2D materials and 2D/organic heterojunctions.
Keywords: defect neutralization; laser soaking; organic/transition metal oxide; photoluminescence quantum yield; transition metal dichalcogenides.