Modifying the Surface Properties of Indium Tin Oxide with Alcohol-Based Monolayers for Use in Organic Electronics

Transparent conductive oxides (TCOs) serve a critical function in many devices, such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). To optimize the performances of these devices, it is desirable to tune the interface between the TCO and the next functional layer of these devices. Self-assembled monolayers prepared from phosphonic acids and silanes are commonly used to tune the properties and performance of this interface, including its surface energy, work function, and durability. Here, we report a new form of self-assembled monolayers for modifying indium tin oxide (ITO), a standard TCO used in OLEDs and OPVs. The ITO surfaces were modified with a series of distinct alcohol reagents. Stabilities of these alcohol-based monolayers were compared with modifications derived from silanes and phosphonic acids, which are commonly used in the literature and industrial processes. Work functions and surface energies of these modified substrates were determined using ultraviolet photoelectron spectroscopy and contact angle measurements. Stability of these monolayers was assessed using cyclic voltammetry, X-ray photoelectron spectroscopy, and transmission spectroscopy techniques. On the basis of the results of these studies, alcohol-based monolayers are promising candidates to modify ITO substrates for use in OLEDs and OPVs.