High-contrast and fast electrochromic switching enabled by plasmonics

Ting Xu,Amit Agrawal,Erich C Walter,Christopher Bohn,A Alec Talin,Jeyavel Velmurugan,Wenqi Zhu,Henri J Lezec

doi:10.1038/ncomms10479

Abstract

With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. Here we achieve fast, high-contrast electrochromic switching by significantly enhancing the interaction of light—propagating as deep-subwavelength-confined surface plasmon polaritons through arrays of metallic nanoslits, with an electrochromic polymer—present as an ultra-thin coating on the slit sidewalls. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films, while maintaining the high optical contrast associated with thicker electrochromic coatings. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer.

Highlights

With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices
The working electrode designed for monochromatic operation incorporates an Au film patterned with a nanoslit array and conformally coated with a thin layer of PANI (‘Au-nanoslit’, Fig. 1a)
Light normally incident on the Au-nanoslit array couples to surface plasmon polariton (SPP) travelling both as surface waves along the illuminated Au surface and as guided modes in the nanoslits, with field maxima occurring at the Au-polymer interfaces

Summary

Introduction

With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. Slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer. A typical multi-colour electrochromic display requires at least three separate electrochromic materials to provide the colours necessary to make an additive, red–green–blue, or a subtractive, cyan–magenta–yellow, colour palette These three separate layers can require up to six layers of transparent conductors to operate, raising production complexity, cost and further limiting the switching contrast. The plasmonic electrochromic switchable configurations retain the advantages of both fast switching speed and high optical contrast

Methods

Results

Conclusion