Full-Color-Tunable Nanophotonic Device Using Electrochromic Tungsten Trioxide Thin Film.

Lee, Yohan; Yun, Jeongse; Seo, Minjee; Kim, Sun-Je; Oh, Jaehyun; Kang, Chung Mu; Sun, Ho-Jung; Chung, Taek Dong et al. · Nano Lett · 2020

basic_science · Level V

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Abstract

Color generation based on strategically designed plasmonic nanostructures is a promising approach for display applications with unprecedented high-resolution. However, it is disadvantageous in that the optical response is fixed once the structure is determined. Therefore, obtaining high modulation depth with reversible optical properties while maintaining its fixed nanostructure is a great challenge in nanophotonics. In this work, dynamic color tuning and switching using tungsten trioxide (WO<sub>3</sub>), a representative electrochromic material, are demonstrated with reflection-type and transmission-type optical devices. Thin WO<sub>3</sub> films incorporated in simple stacked configurations undergo dynamic color change by the adjustment of their dielectric constant through the electrochromic principle. A large resonance wavelength shift up to 107 nm under an electrochemical bias of 3.2 V could be achieved by the reflection-type device. For the transmission-type device, on/off switchable color pixels with improved purity are demonstrated of which transmittance is modulated by up to 4.04:1.