A study of the characteristics of indium tin oxide after chlorine electro-chemical treatment

• We investigated the influence of chlorine surface treatment on ITO properties.
• Chlorination induced the change of the electro-static potential in the outer surface.
• Chlorine electro-chemical treatment of ITO is a simple, fast and effective technique.

In this work, we investigate the influence of a chlorine-based electro-chemical surface treatment on the characteristics of indium tin oxide (ITO) including the work function, chemical composition, and phase transition. The treated ITOs were characterized using X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS), 4-point probe measurements, and grazing incidence X-ray diffraction (GI-XRD).We confirmed a change of the chemical composition in the near-surface region of the ITO and the formation of indium-chlorine (In-Cl) bonds and surface dipoles (via XPS). In particular, the change of the electro-static potential in the outer surface was caused by chlorination.Due to the vacuum-level shift after the electro-chemical treatment in a dilute hydrochloric acid, the ITO work function was increased by ∼0.43 eV (via UPS); furthermore, the electro-negativity of the chlorine anions attracted electrons to emit them from the hole transport layer (HTL) to the ITO anodes, resulting in an increase of the hole-injection efficiency.

The presence of Chlorine in the outer surface resulted in a highly electro-negative surface states and an increase in the vacuum energy level.Figure optionsDownload as PowerPoint slide