Review article: tuning the gold electrode work function with thiol-based self-assembled monolayers

Self-assembled monolayers (SAMs) have emerged as a powerful strategy for interfacial engineering in organic and molecular electronics, enabling control of surface properties such as wettability, adhesion and electrode work function (WF). The WF is a key parameter for charge injection, transport, and device performance. By adjusting molecular design, dipole orientation, and surface coverage, SAMs allow precise tuning the WF, optimizing energy-level alignment in devices such as organic solar cells, organic light-emitting diodes, and organic thin-film transistors. This review focuses on WF modulation of gold electrodes, a widely used material due to its chemical stability, high conductivity, and compatibility with thiol-based SAMs. We provide a comprehensive overview of thiol derived SAMs for gold surface modification, emphasizing their impact on WF as measured by kelvin probe force microscopy (KPFM), kelvin probe (KP), and ultraviolet photoelectron spectroscopy. Key parameters including molecular dipole, packing density, chain length, and terminal groups are discussed, along with the advantages of mixed SAMs for achieving precise WF control. These studies demonstrate that strategic molecular selection enables WF tuning across a broad range of 3.7-6.0 eV on gold surfaces. This review underscores the potential of SAMs as a versatile tool for advancing organic and molecular electronic through tailored interfacial engineering.