Polypyrrole electrochromic performance

Figure 29. (a) Evolution of the absorption spectra of an electro-chromic polypyrrole as a function of the oxidation potential obtained during voltammetry between -900 and 400 mV from a 2.5 M LiCI04 aqueous solution. The voltammetry was performed at a scan rate of 20 mV s 1. (From Ref. 161). (b) Evolution of the absorption spectra of an electrochromic polypyrrole as a function of the reduction potential obtained during voltammetry between 400 and -900 mV from a 2.5 M LiCI04 aqueous solution. The voltammetry was performed at a scan rate of 20 mV s 1. (From Ref. 161). 

Few reports on polypyrrole-based electrochromic devices have appeared due to air instability of the neutral undoped state of the polymer. A polypyrrole-based optical window performing in water has been proposed [423]. DePaoli et al. [424] have produced a device from electrochemically deposited polypyrrole dodecylsulfonate which results in improved properties over polypyrrole doped with perchlorate. 

Electrochromic devices using solid electrolytes have been produced more recently. A device [425] is based on poly(3-octylthiophene) or polypyrrole films with vanadium oxide as a counter-material and poly(ethylen-oxide) as a solid electrolyte. The poor performances (maximum 100 cycles of operation) of these early devices, due to the instability of the materials and the high operating temperature, have been greatly improved by the use of poly(3,4-ethylenedioxythiophene), provided with a low oxidation potential and optimum contrast, and of a poly(ethylenoxide)-poly(phospha-zene) solid electrolyte of high room temperature conductivity [153]. This device may be operated up to 1000 cycles without losses. 

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