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.基于精心设计的等离激元纳米结构的色彩生成技术，是一种极具应用前景的显示方案，可实现前所未有的高分辨率。然而该方案存在固有缺陷：一旦纳米结构确定，其光学响应便固定不变。因此，在保持纳米结构固定的前提下，实现具备可逆光学特性的高调制深度，是纳米光子学领域的一大挑战。本研究以具有代表性的电致变色材料三氧化钨（tungsten trioxide, WO3）为对象，通过反射式与透射式光学器件，实现了动态色彩调谐与色彩切换功能。采用简单堆叠结构制备的三氧化钨薄膜，可通过电致变色原理调控介电常数，进而实现动态色彩变化。反射式器件可在3.2 V的电化学偏置下，实现最大达107 nm的共振波长偏移。透射式器件则实现了色彩纯度提升的可开关色彩像素，其透射率调制比最高可达4.04:1。