| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuE |
| Session: | Thin Film Synthesis & Characterization I |
| Presenter: | Yi Ren, Institute of Materials Research and Engineering, Singapore |
| Authors: | Y. Ren, Institute of Materials Research and Engineering, Singapore S.Y. Chiam, Institute of Materials Research and Engineering, Singapore J. Liu, Institute of Materials Research and Engineering, Singapore |
| Correspondent: | Click to Email |
Electrochromic (EC) thin films are important for enabling technologies such as smart windows and non-volatile displays. To date, various organic EC films have been shown to possess high coloration efficiency and many color variety, while inorganic films have demonstrated excellent optical modulation and cycling stability. In addition, flexible EC devices that are retrofittable to existing windows can also be achieved by utilizing organic or porous inorganic films, and this poses new challenges in device integration and performance enhancement. In this presentation, I will first talk about various synthesis methods used by us for EC thin film deposition. Solution-based methods which target for low-cost and large-scale fabrication will be emphasized. Besides chemical bath deposition and electroplating, an innovative dip coating method with better thickness control will be introduced. Materials covered range from inorganic metal oxides (such as nickel, tungsten, molybdenum and tantalum oxide) to organic polymer electrolytes. We found that different synthesis methods result in films with different structure, phase and defect density. These differences in turn significantly affect the electrochromic performance of the material. Therefore, in the second part of the presentation, I will focus on characterizing and correlating the physical and electrochromic properties of the synthesized films. As an example, layered nickel oxide/hydroxide will be discussed in details. With different synthesis methods and post treatments, we are able to investigate the electrochromic performance of films with different structures (compact, porous and nanostructured), phases (α and β phase), defect density (amount of Ni3+ sites) and intercalated species (water and anions). By changing electrolyte, we can also study the role of different ions in causing the color change, in particular, H+, OH- and Li+. Recently, we have successfully identified the causes of the activation and degradation phenomenon observed in oxide material. We have also proved the importance of having existing reaction sites such as defects for improved electrochromic reaction involving Li+. The above knowledge can be extended to other layered material such as tungsten and molybdenum oxides. Last but not least, our ongoing work also focuses on synthesizing and characterizing thin films that can be functioned as solid electrolyte in electrochromic device. Besides the organic polymer electrolyte, we also look at emerging inorganic metal oxide electrolyte such as tantalum oxide. Their synthesis and ion conducting properties play significant role in device integration and performance.