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Color combination of conductive polymers for black electrochromism
Haijin Shin1, Yuna Kim, Thiruvelu Bhuvana
1Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Korea.
ACS Applied Materials & Interfaces
|December 14, 2011
Summary
Researchers developed black electrochromic devices using conducting polymers that absorb red, green, and blue light, combined with a yellow polymer. This RGBY device achieves black color and maintains its state for 200 hours.
Area of Science:
- Materials Science
- Electrochemistry
- Polymer Science
Background:
- Electrochromic devices (ECDs) are crucial for smart windows and displays.
- Achieving a true black color in ECDs requires broad absorption across the visible spectrum.
- Current ECDs often struggle with achieving deep black hues and long-term stability.
Purpose of the Study:
- To engineer a black electrochromic device (ECD) by combining red, green, and blue (RGB) absorbing polymers with a yellow electrochromic polymer (Y).
- To achieve a broad absorption spectrum in the visible range for a near-perfect black color.
- To evaluate the colorimetric properties and memory effect of the developed RGBY ECD.
Main Methods:
- Fabrication of a complementary ECD by coating RGB-absorbing polymers (poly(3-hexylthiophene) for red, poly(3,4-ethylenedioxythiophene) for blue, poly(aniline-N-butylsulfonate) for green) on one electrode.
- Coating a yellow electrochromic polymer (poly{[1,3-bis(9 elevant',9 elevant'-dihexylfluoren-20-yl)azulenyl]-alt-[2",7"-(9",9"-dihexylfluorenyl]}) on the opposing electrode.
- Characterization of the ECD's colorimetric properties (CIE L*, a*, b*) and memory effect over 200 hours.
Main Results:
- The yellow electrochromic polymer (PDHFA) effectively compensated for absorption gaps in the RGB electrode below 450 nm and above 600 nm.
- The resulting RGBY ECD exhibited a black color with CIE values L*=32, a*=-1.1, and b*=3.7, indicating broad visible light absorption.
- The black state of the ECD was stably maintained for 200 hours after power removal, demonstrating a significant memory effect.
Conclusions:
- The strategic combination of RGB and yellow electrochromic polymers enables the creation of high-performance black ECDs.
- The developed RGBY ECD offers excellent colorimetric properties and long-term stability, suitable for advanced display and smart window applications.
- This approach provides a viable pathway for engineering spectrally broad electrochromic devices with memory capabilities.
