Investigation of Ag-TiO<sub>2</sub> Interfacial Reaction of Highly Stable Ag Nanowire Transparent Conductive Film with Conformal TiO<sub>2</sub> Coating by Atomic Layer Deposition

The atomic layer deposition (ALD) technique is applied to coat Ag nanowires (NWs) with a highly uniform and conformal TiO<sub>2</sub> layer to improve the stability and sustainability of Ag NW transparent conductive films (TCFs) at high temperatures. The TiO<sub>2</sub> layer can be directly deposited on Ag NWs with a surface polyvinylpyrrolidone (PVP) coat that acts a bed for TiO<sub>2</sub> seeding in the ALD process. The ALD TiO<sub>2</sub> layer significantly enhances the thermal stability at least 100 fold when aged between 200–400 °C and also provides an extra function of violet-blue light filtration for Ag NW TCFs. Investigation into the interaction between TiO<sub>2</sub> and Ag reveals that the conformal TiO<sub>2</sub> shell could effectively prevent Ag from 1D-to-3D ripening. However, Ag could penetrate the conformal TiO<sub>2</sub> shell and form nanocrystals on the TiO<sub>2</sub> shell surface when it is aged at 400 °C. According to experimental data and thermodynamic evaluation, the Ag penetration leads to an interlayer composed of mixed Ag–Ag<sub>2</sub>O-amorphous carbon phases and TiO<sub>2–<i>x</i></sub> at the Ag–TiO<sub>2</sub> interface, which is thought to be caused by extremely high vapor pressure of Ag at the Ag–TiO<sub>2</sub> interface at a higher temperature (e.g., 400 °C).