Monolayer transition-metal dichalcogenides MX₂ (M = Mo, W; X = S, Se, Te) have attracted much attention for use in electronic and optical applications. Due to their sensitivity to gases, the surface of these materials has been protected by coating with polymers such as polyethyleneimine (PEI). However, the effects of such coating layers on the electronic and optical properties of MX₂ are not well understood. In this work, density functional theory calculations are used to study the effects of adsorption of PEI on monolayer MX₂ substrates based on the electronic and optical properties before and after PEI adsorption. The results show that the bandgap of the substrate decreases significantly upon PEI adsorption, while the optical spectra show only slight modification with a decrease of intensity at short wavelengths around 300 nm. The results also indicate that PEI adsorption results in n-type doping states in MX₂ but does not deteriorate the optical properties in the visible range.

单层过渡金属二硫属化物MX ₂（中号 =钼，钨; X  = S，硒，碲）而备受关注电子和光学应用。由于它们对气体的敏感性，这些材料的表面已通过涂以聚合物（例如聚乙烯亚胺（PEI））进行保护。但是，这种涂层对MX ₂的电子和光学性能的影响尚不清楚。在这项工作中，使用密度泛函理论计算来研究PEI在单层MX ₂上的吸附作用根据PEI吸附前后的电子和光学特性确定基材。结果表明，PEI吸附后基材的带隙显着降低，而光谱仅显示出轻微的变化，并且在300 nm左右的短波长处强度降低。结果还表明，PEI吸附在MX _2中导致n型掺杂状态，但不会降低可见光范围内的光学性能。