The Origins of Solid-Solid Contact Electrification

Solid-solid contact electrification (CE) is the elementary process of triboelectricity, which describes the charge transfer phenomenon between solid contact materials. Though the triboelectric effect has been observed and studied for centuries, the origin of CE remains as one of the most debatable topics for the scientific community. In this chapter, the historical and current understanding of the origins of solid-solid CE has been reviewed. The discussion starts with the most established metal-metal contact systems, where electron transfer model provides an excellent explanation of their CE behaviors, followed by a comprehensive review of insulator system considering electronic as well as surface chemical effects. Emerging experimental techniques (scanning probe microscopy, photon emission spectroscopy, etc.) and theoretical approaches (density functional theory, atomistic model, quantum dynamics) that advance fundamental understanding of solid-solid CE are also discussed. Lastly, emerging solid-solid CE involving semiconductor is introduced.