Avoiding Voltage-Induced Degradation in PET-ITO-Based Flexible Electrochromic Devices.

Area of Science:

• Materials Science
• Electrochemistry
• Device Engineering

Background:

• Flexible electrochromic devices (ECDs) are promising for various applications.
• Cycling stability of flexible ECDs is limited by indium tin oxide (ITO) degradation under humid conditions.
• ITO reduction leads to device failure through dissolution and metallic indium formation.

Purpose of the Study:

• To develop and test a strategy to enhance the cycling stability of flexible ECDs under humid atmospheres.
• To investigate the degradation mechanism of ITO in flexible ECDs.
• To optimize device configuration to prevent ITO reduction.

Main Methods:

• Fabrication of model ECDs using a sidechain-modified poly(3,4-ethylene dioxythiophene) (PEDOT) derivative and Prussian blue (PB).
• Utilized ECDs with an auxiliary reference electrode to monitor actual electrode potentials.
• Adjusted the electrode charge density ratio to control the overall cell voltage window.

Main Results:

• ITO degradation is dependent on applied electrode potentials and moisture ingress.
• Adjusting the electrode charge density ratio effectively narrowed the cell voltage window, preventing ITO reduction.
• Optimized ECDs demonstrated significantly improved cycling stability under 90% relative humidity without performance impairment.

Conclusions:

• A novel strategy of adjusting electrode potentials prevents irreversible ITO reduction in flexible ECDs.
• The proposed method enhances device durability under humid conditions, paving the way for commercialization.
• Optimized flexible ECDs maintain performance while achieving superior long-term stability.