Baek, Kyungnae Kim, In Soo Eum, Yejin Moon, Cheon Woo Hyun, Jerome K. 2025-03-21T08:30:10Z 2025-03-21T08:30:10Z 2025-03-19 2025-06 2195-1071 https://pubs.kist.re.kr/handle/201004/151957 The degree of optical modulation per unit charge per area, known as the coloration efficiency, is a crucial figure of merit for evaluating the performance of electrochromic devices. Typically, the coloration efficiencies of most organic and inorganic electrochromic materials have lagged behind those of liquid crystal devices, reaching values in the range of one to two orders of cm(2)/C. As reflective electrochromics gain importance in applications like colored e-paper and smart labels, enhancing their coloration efficiency becomes essential. Here, a wide range of vibrant colors is demonstrated resulting from birefringent mechanisms in a WO3 nanograting and achieve reflective coloration efficiencies exceeding 2100 cm(2 )C(-1) upon lithiation. The lithiation reduces the grating birefringence, dramatically enhancing the blackness, which results in superior coloration efficiencies beyond improvements from engineering the intrinsic properties of WO3. Additionally, unlike other strategies based on resonant cavities that display changing colors during intensity variations due to the modified refractive index upon lithiation, the approach ensures consistent hues over all intensity levels as the colors are primarily determined by the fixed period rather than the shifting refractive index. These results suggest new pathways for achieving high-performance reflective electrochromic devices. English John Wiley and Sons Inc. Superior Coloration Efficiencies in Reflective Multicolor Electrochromics with Birefringent WO3 Nanogratings Article 10.1002/adom.202500319 1 Advanced Optical Materials, v.13, no.18 Advanced Optical Materials 13 18 N scie scopus 001443959600001 Materials Science, Multidisciplinary Optics Materials Science Optics Article PLASMONIC METASURFACES high contrast switching WO3 Li ion intercalation color efficiency electrochromics