Polythiophene -viologen bilayer for electro-trichromic device

• Published in: Solar energy materials and solar cells Vol. 188; pp. 249 - 254
• Main Authors: Chaudhary, Anjali, Pathak, Devesh K., Mishra, Suryakant, Yogi, Priyanka, Sagdeo, Pankaj R., Kumar, Rajesh
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-12-2018; Elsevier BV
• Subjects: Bias; Color; Coloration; Domains; Electrochromic; Electrochromic cells; Electrochromism; Ethylene oxide; Free radicals; Glass substrates; P3HT; Polarity; Polyethylene; Polyethylene oxide; Polythiophene; Smart materials; Switching; Viologen; Electrochromic; Viologen; P3HT
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2018.08.029

An electrochromic device, capable of three-level color switching, has been envisaged by exploiting different color switching properties of Ethyl viologen (EV) and Poly (3-hexylthiophene) (P3HT) to make them switch in congruence with each other. The device, consisting of an EV/P3HT bilayer in poly-ethylene oxide matrix, appears magenta, blue or transparent under an appropriate bias. The unbiased device shows magenta colored appearance and turns transparent at a bias of 1 V when P3HT layer is used as anode. The device turns blue on increasing the bias to 1.4 V without changing the polarity. The mechanism of multilevel switching has been identified using UV–Vis and Raman spectroscopic investigations which reveal that the 1 V bias converts the P3HT into polarons and 1.4 V converts the EV dications (EV2+) into free radical. The electrochromic device demonstrates better color contrast (~ 50%) in both the optical domains. The fabricated device shows better switching speeds of ~ 1.5 s and good stability and coloration efficiency along with three-level color switching. However the reported device uses ITO coated glass as substrate, it can be used for all-organic flexible electrochromic device.
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•Multistage electrochromic device by exploiting electrochromism of P3HT-viologen.•Enhancement in electrochromic performance parameters.•Electrolyte free electrochromic device designed for power efficient operation.•Paving way for all-organic flexible electrochromic device.