Thermal Cross-Linking preparation of Aqueous-Based cathodic films for enhanced stability in organic electrochromic devices

Abstract

Four derivatives of naphthalene diimide (NDI) small molecules with different polar functional side chains were designed and synthesized. The corresponding polymers, PNDI-5C/8C/DC/TC, were further prepared by thermal cross-linking method and utilized to fabricate organic electrochromic films. All of the PNDI-5C/8C/DC/TC films exhibit solvent resistance characteristics in commonly used organic solvents and water, and they possess varied surface energies, reduction voltages and electrochemical stabilities in aqueous electrolytes. The PNDI-TC film, which has the highest hydrophilicity, has a high optical contrast of 43.3 % with a short coloring time of 1.9 s and bleaching time of 0.6 s. Most importantly, the performance of the organic electrochromic device based on PNDI-TC can maintain almost 100 % contrast after 1000 cycles, showing great potential in the application of aqueous-based organic electrochromic device.