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Intrinsically stretchable polymer based electrochromic devices for soft electronic displays

University of British Columbia

In soft electronics technology, stretchable displays move away from conventional rigid devices to adopt mechanical properties more similar to organic materials while preserving function, leading to more conformable and biointegrable devices. Progress has been made on luminescent stretchable displays; however, electrochromic materials that change colour instead of emitting light provide key advantages of low power operation, stability and high contrast. Despite this, development of stretchable electrochromic displays has been limited. In this thesis we demonstrate the first intrinsically stretchable fully integrated electrochromic display device. A poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) conducting polymer and (1-butyl-3-methylimidazolium octyl sulfate) ionic liquid conductive composite is used as the intrinsically stretchable electrochromic electrodes, with a stretchable polyvinyl alcohol and phosphoric acid-based electrolyte and transparent styrene-based elastomer substrate to form a single pixel device. Both a transparent and reflective opaque version of the device are made. High contrasts up to ΔTmax=15% for transparent and ΔRmax=20% for opaque cells are shown, and optical modulation degradation as low as ΔT or ΔR=1-3% is shown when the samples are strained from 0% to 30% length. Under 30% strain they show fast switch times <7 s, high contrast for up to 500 electrochemical cycles, and low power operation. They perform comparably to other PEDOT based flexible electrochromics with the added benefit of stretchability. A 3×3 passive matrix display is fabricated and high contrast low cross talk single pixel activation addressability is demonstrated under 0% and 30% strain, the first intrinsically stretchable multi-pixel electrochromic display. Fabrication is performed using solution-processing techniques with low cost materials, enabling easy potential scale up. An optical and electrochemical characterization setup is developed to measure performance under strain. An electrochemical technique is newly demonstrated to investigate half cell potentials in the solid-state electrochromic cell as a method for investigating degradation. Overall, an advance is demonstrated in the direction of intrinsically stretchable displays based on electrochromics. Applications include compliant, low cost, visual display interfaces for conveying information, such as physiological monitoring patches, wearable electronics, camouflage coverings, multifunctional tactile platforms, or robotic skin.

Text

2020-08-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/75726

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/