Electrochromic polymers based flexible electrochromic devices have been sought after by industry for the manufacture of low-cost, low-waste and high performance products. Further, necessary colors are in demand for numerous applications. A neutral color is a color not associated with any single hue, provides an unmitigated view of the environment without distorting original colors. It minimizes eye fatigue and provides a calm, non-distractive atmosphere. ECDs that exhibit gray/black/neutral colors are of great interest in architectural/smart windows, automotive applications and eyewear. Following theoretical calculations of a number of combinations of electrochromic materials, two systems demonstrated military neutrality (a measure of the variability of absorption heights across the visible range, weighted to the sensitivity of the human eye, ≤12%) via single-lamination approach. In situ electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) and the copolymer of (2,2 dimethyl-3,4-propylenedioxythiophene) (ProDOT-Me2) and 1,3-di-tert-butyl-3,4-propylenedioxythiophene (ProDOT-tBu2) was used in system I, which switches between two neutral colors (light blue and gray). System II provides an alternative fabrication procedure by combining in situ electrochemical polymerization of 3,4-ethylenedioxythiophene (EDOT) and spray coating of 1,4-phenylene-3,4-propylenedioxythiophene (ProDOT-Ph), which switches among three colors (light blue, gray and orange). Both systems exhibit photopic contrasts of 41% without background correction when assembled with anti-reflection indium doped tin oxide glass. In addition, devices exhibit switching speeds of less than 2 seconds, and have good color uniformity. A 60cm2, defect-free flexible ECDs were fabricated and characterized, exceeding the size of small displays.

Neutral color tuning of flexible conjugated polymer electrochromic devices achieved by multi-component systems

253rd National Meeting (2017)

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