Electrochromic Device Assembly

To investigate the electrochromic performance, transparent devices were assembled similarly to Sect. 5.2.3 by capping the prepared NiO films with a FTO counter electrode using a precut thermoplastic gasket as spacer, infiltration with 1M KOH(aq) electrolyte, insertion of an Ag/AgCl wire as reference electrode, and finally sealing the device with epoxy glue. 

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PENNARUN, P.Y., JANNASCH, p., PAPAEFTHiMiou, s., et al.. High coloration performance of electrochromic devices assembled with electrolytes based on a branched boronate ester polymer and lithium perchlorate salt. Thin Solid Films, 2006,514,258-66. 

Sheng, K. Bai, H. Sun, Y. Li, C. Shi, G., Layer-by-layer assembly of graphene/polyaniline multilayer films and their application for electrochromic devices. Polymer 2011. 

In conclusion, this book is intended as an overview of the principles behind and state-of-the-art in interfacial supramolecular chemistry. The book is suitable for researchers and graduate students and focuses on assemblies that demonstrate at least the potential to produce useful devices such as solar cells, electrochromic devices, molecular wires, switches and sensors which are addressable by using electrochemical and optical stimuli. Molecular materials for nanoscale molecular devices remain an intriguing conceptual possibility. 

It is somewhat surprising that electrochromic devices have also been reported. TiC>2 is not electroactive at potentials where the molecular components are. However, electron transport to the underlying ITO surface through an electron-hopping process drives the electrochemical process. A very fast electrochromic device has been developed, further suggesting considerable potential of these assemblies for commercial applications. 

Fig. 5.3 Electrochromic cell assembly, a Schematic illustration of the layered device design based on a DG-structured electrode, b Functional electrochromic nano-device with the design pattern in the chromogenic double-gyroid film showing the crest of the University of Cambridge. The thickness of the vanadia deposit was measured to be around 1.1 p.m...

Nguyen, C.A., Argun, A.A., Hammond, P.T., Lu, X., Lee, P.S., 2011. Layer-by-layer assembled solid polymer electrolyte for electrochromic devices. Chem. Mater. 23,2142-2149. 

C. H. Yang, Y. K. Chih, W. C. Wu, C. H. Chen, Molecular assembly engineering of self-doped polyaniline film for application in electrochromic devices, Electrochemical and Solid State Letters 2006, 9, C5. 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

In this section, the constmction of electrochromic devices whose principle electrochromic materials are polythiophenes is discussed. 3-Substituted polythiophenes are the most popular electrochromic materials for such devices. A solid-state electrochromic device was assembled by using poly[3-[12-(p-methoxyphenoxy)dodecyl]thiophene] and poly(3,4-ethylenedioxythiophene) doped with poly(styrene-sulfonate), which showed a color variation from red in the reduced state to blue in the oxidized state during ca. 500 charge-discharge cycles [80]. 

Dual-type absorptive/transmissive polymer electrochromic devices based on poly[thiophen-3-ylacetic acid 4-pyrrol-1-ylphenyl ester (TAPE)-co-A -methylpyrrole (NMPy)] and PEDOT have been assembled, which exhibit good optical memory, stability with moderate switching times and light yellow and green colors upon doping and dedoping, respectively [82],... 

The differences in the final properties of the copolymer according to the monomer s feed ratio were also observed for P(DHQT-co-DNBP) (12) films electrodeposited onto ITO/glass. DHQT is a fluorescent thiophene oligomer usually applied as active layer for assemble of organic field effect transistors (OFETs)/ photovoltaic cells and electrochromic devices/ while the polymer PDNBP and its copolymer with EDOT have... 

Akhtar et al. [902(a)] were one of the first to describe completely assembled, sealed, solid-state electrochromic devices based on CPs. In one set of devices, the fairly common Li-triflate/Poly(ethylene oxide) (PEO)/acetonitrile formulation for nonaqueous solid electrolytes was used. However, in another set, the unique combination of poly(ethyleneimines) of different MWt and protonic acids such as hydrochloric, sulfuric, phosphoric, acetic and poly(styrene sulfonic) was used. Additionally, the films of the CP, P(ANi), were prepared electrochemically as well as by sublimation, and in one set of devices Fe-tungstate was used as a counter electrode to provide a definitive counter electrode reaction (Lithiation). While cyclabilities to several thousand cycles were claimed, the electrochromic dynamic range and other parameters were fairly poor, as seen in Figs. 20-3. Very rapid switching times have been claimed for many P(ANi)- or P(ANi)-derivative based devices. For example. Ram et al. [902(b)] claimed a 143 ms switching time for liquid-electrolyte devices based on poly(aniline-co-o-anisidine). 

PEDOT has been found to have useful electrochromic properties - and for a long time fed the hope of inexpensive electrochromic glazings made by simple coating techniques for architectural and automobile applications. At present it seems unlikely that PEDOT-based electrochromic glazings will appear on the market in the near future. However its potential has inspired numerous and continuing studies that intend to improve the properties of the electrochromic solid, the electrolyte, and the ion storage material and to assemble innovative electrochromic devices. 

D. DeLongchamp and P. T. Hammond. 2001. Layer-by-layer assembly of PEDOT/polyaniline electrochromic devices. Adv Mater 13(19) 1455-1459. 

Jain V, Yochum H, Wang H, Montazami R, Hurtado MAV, Mendoza-Galvan A, Gibson HW, Heflin JR (2008) Solid-state electrochromic devices via ionic self-assembled multilayers (ISAM) of a polyviologen. Macromol Chem Phys 209 150-157... 

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