Octa-viologen substituted polyhedral oligomeric silsesquioxane exhibiting outstanding electrochromic performances

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 393; p. 124690
• Main Authors: Pande, Gaurav K., Choi, Jun Hong, Lee, Jung-Eun, Kim, Yea Eun, Choi, Jin Hui, Choi, Hye Won, Chae, Han Gi, Park, Jong S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2020
• Subjects: Coloration efficiency; Electrochromic property; Mechanical and thermal property; POSS-viologen; Switching speed; Electrochromic property; Mechanical and thermal property; POSS-viologen; Coloration efficiency; Switching speed
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2020.124690

•We synthesized octa-hexyl viologen substituted polyhedral oligomeric silsesquioxane (OHV-POSS).•Electrochromic devices were fabricated using OHV-POSS incorporated ion gel compositions.•The prepared device showed excellent electrochromic properties and switching stability.•Flexible electrochromic devices were fabricated on silver nanowire-PEDOT:PSS composite electrodes.•The fabricated device exhibited superb electrochromic performance with repeated bending cycles. We present a new strategy for improving the electrochromic properties of single-layered ion gels for electrochromic devices (ECDs) by incorporating octa-hexyl viologen substituted polyhedral oligomeric silsesquioxane (OHV-POSS). Newly synthesized OHV-POSS was included in ion gel compositions containing a poly(vinylidene fluoride) copolymer and ionic liquid to produce a freestanding film. When applied in single-layered ECDs, due to high ionic conductivity and fast charge transfer, the OHV-POSS film exhibited outstanding electrochromic performances with low redox potentials at −1.1 V, high transmittance changes (ΔT) of 56.1%, and a moderate coloration efficiency (CE) of 124.1 cm2/C. When combined with isooctyl polyhedral oligomeric silsesquioxane (IO-POSS), the device performances were remarkably enhanced, exhibiting a ΔT of 67.2% and CE of up to 307.8 cm2/C. In addition, the fabricated device maintained its switching stability for up to >12,000 cycles with a switching speed of 8.6 s. The electrochromic improvement is attributed to the presence of a POSS (Si-O-Si) cross-linkable cage structure featuring robust mechanical properties. In addition, flexible ECDs were fabricated on silver nanowire-PEDOT:PSS composite electrodes, and superb electrochromic performances were achieved with repeated bending cycles (>200 cycles). This study’s results present a promising tool for the material design of high-performance stable ECDs for long-term operation in displays, eyewear, and transmissive windows.