Phosphonic Acids for Interfacial Engineering of Transparent Conductive Oxides

TLDR: This review surveys the literature on TCO modification with phosphonic acids (PAs), which has increasingly been used to engineer these interfacial properties in organic-semiconductor devices and discusses the relevance of TCO surface modification to organic electronics.

Abstract: Transparent conducting oxides (TCOs), such as indium tin oxide and zinc oxide, play an important role as electrode materials in organic-semiconductor devices. The properties of the inorganic–organic interface—the offset between the TCO Fermi level and the relevant transport level, the extent to which the organic semiconductor can wet the oxide surface, and the influence of the surface on semiconductor morphology—significantly affect device performance. This review surveys the literature on TCO modification with phosphonic acids (PAs), which has increasingly been used to engineer these interfacial properties. The first part outlines the relevance of TCO surface modification to organic electronics, surveys methods for the synthesis of PAs, discusses the modes by which they can bind to TCO surfaces, and compares PAs to alternative organic surface modifiers. The next section discusses methods of PA monolayer deposition, the kinetics of monolayer formation, and structural evidence regarding molecular orientati...