|M.Sc Student||Buchbinder Lotem|
|Subject||Hybrid Electrochromic Materials|
|Department||Department of Materials Science and Engineering||Supervisor||Professor Gitti Frey|
|Full Thesis text|
Electrochromic materials change their optical properties reversibly and persistently while undergoing an electrochemical process. Such materials are utilized in a variety of energy-saving applications including smart windows and display devices.
The main objective of this research was to design, prepare and study electrochromic hybrid materials by synergistically combining organic and inorganic electrochromic materials. The hybrid system should allow multicolor functionality and attain improved chemical and environmental stability .
In this context, electrochromic conjugated polymers or small organic electrochromic molecules were combined with inorganic electrochromic tungsten oxide. The structure and composition of the hybrid films were characterized using scanning electron microscopy, while the optical and electrochromic performance were studied through cyclic voltammetry and optical spectroscopy under applied bias.
In the hybrid materials we developed the tungsten oxide was a porous scaffold that incorporated the organic electrochromic species, either perylene diimide (PDI) or a conjugated polymer of the polythiophene family: PMeT, PEDOT or PEDOT_C6.
The tungsten oxide/Br2PDI system showed multicolor functionality in aqueous solution, but was unstable due to the solubility of the diimide dianion is the solution. In the case of the polymers, the organic character of PMeT limited its monomer infiltration into the tungsten oxide porous scaffold and its activity in acidic solutions. Hence, the hydrated tungsten oxide/PMeT device was fabricated by positioning both materials side by side, and showed multicolor functionality in organic solutions. The PEDOT and PEDOT_C6 were successfully incorporated into the tungsten oxide scaffold and showed electrochromic performance in acidic solutions. However, the color states and redox potentials of PEDOT are similar to those of tungsten oxide so that only two colors, blue and transparent, were obtained. Finally, multi (3) color-changes in an acidic solution and enhanced stability was achieved in the PEDOT_C6/WO3 system. Hence, we have demonstrated that, judicious selection of organic and inorganic electrochromic materials allows their synergistic combination to attain hybrid multi-color electrochromic materials.