DEVELOPMENT OF HIGH PERFORMANCE ELECTROCHROMIC MATERIALS AND THEIR DEVICES

Abstract

This thesis focuses on electrochromic conjugated polymers – materials which exhibit reversible color and transmittance changes upon an electrical stimulus, and seeks to provide a deeper understanding on the fundamental chemistry and physics behind their operationality as well as to explore methods to optimize their performances. In this project, donor-acceptor type diketopyrrolopyrrole-based polymers in their fabricated devices are investigated. This includes the analysis of the influence of chemical compositions on the hues of the polymers, from which guidelines for color-tuning of such materials are developed and illustrated. Detailed structure-property relationship studies are also carried out, which examines how variations in the chemical makeup of the polymers in terms of length of side chains, molecular weight and donor-to-acceptor ratio affect their electrochromic performances. The critical role of the polymer film morphology is substantiated and efforts to enhance the electrochromic properties through morphological control strategies such as solvent vapor annealing and polymer nano-structuring are attempted.