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

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
(WO3), a representative electrochromic material, are demonstrated
with reflection-type and transmission-type optical devices. Thin WO3 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.