Designing tunable molecular devices with different charge carriers in single-molecule junctions is crucial to the next-generation electronic technology. Recently, it has been demonstrated that the type of charge carriers depends on and can be tuned by controlling the molecular length and the number of interfacial covalent bonds. In this study, we show that the type of charge carriers can also be tuned by controlling the material and shape of electrodes. N-heterocyclic carbenes (NHCs) have attracted attention because of their ability to form strong, substitutional inert bonds in a variety of metals. Also, NHCs are more stable than the widely used thiol group. Therefore, we use electrodes to tune the type of charge carriers in a series of NHCs with different side groups. The ab initio calculations based on non-equilibrium Green’s formalism combined with density functional theory show that the dominant charge carrier switches from electrons to holes when gold electrodes are changed into platinum ones. The nature of the charge carriers can be identified by variations in the transport spectra at the Fermi level (E _F), which are caused by the side groups. The projections of transport spectra onto the central molecules further validate our inferences. In addition, the transmission coefficient at E _F is found to be dependent on the atomic interface structure. In particular, for the NHC without methyl or ethyl side groups, connecting a protruding atom on the electrode surface significantly enhances the transportability of both electrode materials. Overall, this study presents an effective approach to modifying transport properties, which has potential applications in designing functional molecular devices based on NHCs.

在单分子结中设计具有不同电荷载流子的可调谐分子器件对于下一代电子技术至关重要。最近，已经证明电荷载流子的类型取决于并且可以通过控制分子长度和界面共价键的数量来调节。在这项研究中，我们表明电荷载体的类型也可以通过控制电极的材料和形状来调整。N-杂环卡宾 (NHCs) 因其在多种金属中形成强取代惰性键的能力而备受关注。此外，NHC 比广泛使用的硫醇基团更稳定。因此，我们使用电极来调整一系列具有不同侧基的 NHC 中的电荷载流子的类型。从头算基于非平衡格林形式主义结合密度泛函理论的计算表明，当金电极变为铂电极时，主要的电荷载流子从电子转变为空穴。电荷载流子的性质可以通过费米能级 ( _EF ) 的传输光谱变化来识别，这是由侧基引起的。传输光谱在中心分子上的投影进一步验证了我们的推论。此外，E _{F处的传输系数} 发现依赖于原子界面结构。特别是对于没有甲基或乙基侧基的 NHC，在电极表面连接一个突出的原子可显着提高两种电极材料的可传输性。总体而言，本研究提出了一种改变传输特性的有效方法，在设计基于 NHC 的功能性分子装置方面具有潜在应用。