RGB-to-black multicolor electrochromic devices enabled with viologen functionalized polyhedral oligomeric silsesquioxanes

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 420; p. 130446
• Main Authors: Pande, Gaurav K., Heo, Jae Sang, Choi, Jun Hong, Eom, Yu Seon, Kim, Jaehyun, Park, Sung Kyu, Park, Jong S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.09.2021
• Subjects: Electrochromic device; Multi-stacked; Multicolor coverage; Polyhedral oligomeric silsesquioxane; RGB-to-black; Viologen; Multicolor coverage; Viologen; Electrochromic device; Polyhedral oligomeric silsesquioxane; RGB-to-black; Multi-stacked
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.130446

•We prepare octa-viologen functionalized POSS compounds.•POSS-viologen ECDs exhibit RGB electrochromic performances.•The secondary colors are produced by color mixing principle.•The multi-stacked ECDs produce RGB-to-black multicolor coverage.•The ECDs maintain high coloration efficiency and long-term switching stability. Here we demonstrate multicolor electrochromic transitions of viologen functionalized polyhedral oligomeric silsesquioxanes (POSS-viologens). Highly efficient RGB coverage, including black, was successfully achieved with POSS-viologen employed multi-stacked electrochromic devices (ECDs). We prepared octa-viologen functionalized POSS (OHV-POSS) with the insertion of thiophene (OTxHV-POSS) and phenyl (OPhHV-POSS) moiety. The single-layer ion gel ECDs exhibited outstanding electrochromic performances. OTxHV-POSS and OHV-POSS showed red (R) and blue (B) transitions, respectively, with high transmittance changes and superb coloration efficiency. Saturated green (G) was also obtained from the mixture of OPhHV-POSS and OHV-POSS. Furthermore, multi-stacked ECDs were implemented by combining the RGB coloration layers with multiple electrodes. The two-layer ECDs generated intermediate colors, which was fully translated into the color mixing theory. The three-layer device created real black with blackness L∗ of 6.99, covering 12.9% of the NTSC color gamut. The unprecedented RGB-to-black multicolor coverage, not reported elsewhere, is attributable to the reversible color-switching at a low redox potential for extended cyclic operations. Current findings imply that carefully designed POSS-viologens offer a universal route to high-performance and stable multicolor ECDs, offering compatibility with various pixelized color-changing displays and smart windows.