TY - JOUR
T1 - Effects of counter ions on electrochromic behaviors of asymmetrically substituted viologens
AU - Pande, Gaurav K.
AU - Kim, Namhyeon
AU - Choi, Jin Hui
AU - Balamurugan, Gopal
AU - Moon, Hong Chul
AU - Park, Jong S.
N1 - Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/8/1
Y1 - 2019/8/1
N2 - We present effects of counter anions on electrochromic behavior of asymmetrically substituted viologens, 1-hexyl-1′-nonafluorohexyl viologens (HERFVs). For this purpose, two anions, hexafluorophosphate ([PF 6 ] – ) and bis(trifluorosulfonyl)imide ([TFSI] – ), were employed for both HERFVs and 1-butyl-3-methylimidazolium ([BMIM] + )-based ionic liquids. The HERFV-containing electrochromic devices (ECDs) exhibited apparent dependence on the counter ions in terms of optical contrast, switching speed, long-term cyclic stability, coloration efficiency, and memory effect. Specifically, the ECDs based on [HERFV][PF 6 ] 2 showed a redox response at −1.0 V with a color change from colorless to blue. Meanwhile, the coloration of [HERFV][TFSI] 2 appeared at −3.0 V, and a significantly long optical memory effect was observed with unstable cyclic repeatability. We attributed this discrepancy to the nature of counter ions, such as size and electronegativity, which may influence the electron transfer process during redox reactions. These results demonstrated that counter anions can exert a significant impact on the EC behaviors of asymmetrically substituted viologens. The presented approach suggests a potential tool for controlling EC properties of viologen derivatives for applications in transmissive windows and eye wear.
AB - We present effects of counter anions on electrochromic behavior of asymmetrically substituted viologens, 1-hexyl-1′-nonafluorohexyl viologens (HERFVs). For this purpose, two anions, hexafluorophosphate ([PF 6 ] – ) and bis(trifluorosulfonyl)imide ([TFSI] – ), were employed for both HERFVs and 1-butyl-3-methylimidazolium ([BMIM] + )-based ionic liquids. The HERFV-containing electrochromic devices (ECDs) exhibited apparent dependence on the counter ions in terms of optical contrast, switching speed, long-term cyclic stability, coloration efficiency, and memory effect. Specifically, the ECDs based on [HERFV][PF 6 ] 2 showed a redox response at −1.0 V with a color change from colorless to blue. Meanwhile, the coloration of [HERFV][TFSI] 2 appeared at −3.0 V, and a significantly long optical memory effect was observed with unstable cyclic repeatability. We attributed this discrepancy to the nature of counter ions, such as size and electronegativity, which may influence the electron transfer process during redox reactions. These results demonstrated that counter anions can exert a significant impact on the EC behaviors of asymmetrically substituted viologens. The presented approach suggests a potential tool for controlling EC properties of viologen derivatives for applications in transmissive windows and eye wear.
KW - 1-Hexyl-1′-nonafluorohexyl asymmetric viologen
KW - Anion exchange
KW - Counter ion
KW - Electrochromic behaviors
KW - Ionic liquid
UR - http://www.scopus.com/inward/record.url?scp=85064156917&partnerID=8YFLogxK
U2 - 10.1016/j.solmat.2019.04.004
DO - 10.1016/j.solmat.2019.04.004
M3 - Article
AN - SCOPUS:85064156917
SN - 0927-0248
VL - 197
SP - 25
EP - 31
JO - Solar Energy Materials and Solar Cells
JF - Solar Energy Materials and Solar Cells
ER -