The possibility of modifying the work function of electrodes is important for optimizing the energy barriers for charge injection (extraction) at the interface to an organic material. In this paper, we perform density-functional theory calculations to investigate the impact of dithiol-terminated polyethylene glycol [PEG(thiol)] based self-assembled monolayers with different numbers of PEG repeat units on the work function of the Au(111) surface. We find that a monolayer of PEG(thiol) decreases the work function of the Au(111) surface, where the magnitude of this reduction strongly depends on the length of the PEG backbone. The main contribution arises from the dipole due to the adsorption-induced charge rearrangement at the interface. Our work reveals a pronounced odd-even effect that can be traced back to the dipole moment of the PEG(thiol) layer.

中文翻译：

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吸附在Au（111）表面上的PEG（硫醇）的功函数修饰：第一性原理研究

修改电极功函数的可能性对于优化在与有机材料的界面处进行电荷注入（提取）的能垒很重要。在本文中，我们执行密度泛函理论计算，以研究具有不同PEG重复单元数的二硫醇封端的聚乙二醇[PEG（thiol）]基自组装单层对Au（111）表面功函数的影响。我们发现，单层的PEG（硫醇）会降低Au（111）表面的功函数，其中这种降低的幅度强烈取决于PEG主链的长度。主要的贡献来自偶极子，这是由于界面处的吸附诱导的电荷重排。我们的工作揭示了一个明显的奇偶效应，可以追溯到PEG（硫醇）层的偶极矩。