Electrochromic Electrodes with Enhanced Performance: Review of Morphology and Ion Transport Mechanism Modifications

The electrochromic (EC) performance of smart windows is highly dependent on the rate of ions insertion/extraction. A direct way to increase the ion exchange in EC device is to modify the structure of the EC electrodes. Structural changes also affect the electrical conduction between the transparent electrodes and the EC layers, leading to efficient smart windows. In more detail, modifying the structure of the EC electrodes results in an increase in the surface-to-volume ratio, which is combined with the increase in charge transfer reaction between the insertion and extraction of ions. The current review summarizes the enhancement in the EC performance due to the fabrication of nano/microstructures or hybrid structures on the surface of the EC electrodes to increase their surface area. Moreover, metal oxide thin films have poor electrical conduction, which leads to a high charge transport barrier. Accordingly, improving the electrical conductivity of the EC layer is considered another effective strategy to enhance the ion transport between the transparent conductor layer and the EC electrode. This behavior could be applied by combining the transition metal oxide with metallic nanoparticles or suitable organic/inorganic transparent conducting materials.