Controlling Charged State Colors in Triphenylamine-Based Anodically Coloring Electrochromes

Area of Science:

• Materials Science
• Electrochemistry
• Organic Electronics

Background:

• Anodically coloring electrochromic (ACE) molecules are crucial for advanced display and smart window technologies.
• Controlling the color palette and switching stability of ACE materials remains a key challenge.

Purpose of the Study:

• To design and synthesize novel EDOT-TPA molecules with systematically varied electronic properties.
• To investigate the impact of substituent position and electron richness on molecular geometry, electrochemistry, and optoelectronic properties.
• To demonstrate precise control over successive charge states and their corresponding colors in ACE systems.

Main Methods:

• Synthesis of thioalkyl-substituted 3,4-ethylenedioxythiophenes coupled to triphenylamine units (EDOT-TPA).
• Electrochemical characterization (cyclic voltammetry) to determine redox potentials and stability.
• Spectroscopic analysis (UV-Vis-NIR) of electrochemically generated cation radical and dication states.
• Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations for theoretical validation.

Main Results:

• Successfully modulated first and second oxidation potentials (0.03–0.18 V and 0.32–0.46 V vs Fc/Fc+).
• Achieved tunable color generation for cation radical and dication states by controlling electrochemical potential separation.
• Demonstrated selective control over successive charge states using an optically transparent thin layer electrode (OTTLE).
• Correlated substituent effects on electron richness and steric interactions with optical transitions using TD-DFT.

Conclusions:

• The designed EDOT-TPA molecules offer unprecedented control over electrochromic properties.
• Modulating substituents provides a powerful strategy for tuning redox potentials and color generation in ACE materials.
• This work advances the development of molecular systems for vibrant and stable electrochromic applications.