Redox behavior of PEDOT, including its neutral, undoped state

3 Redox behavior of PEDOT, including its neutral, undoped state 

PEDOT salts such as p-toluenesulfonate or tetrachloroferrate and PEDOTiPSS can also be reduced to some extent with strong reducing agents such as hydrazine and hydroxylamine [60]. However, residual charged moieties, easily detectable by IR spectroscopy [61], cannot be removed completely. 

The modification of the redox state of PEDOT will change its morphology [35, 64, 65] and absorption spectrum. Hence its absorption can be tuned electrochemlcally. PEDOT and other PEDOT-type polymers therefore exhibit electrochromic properties, which can be utilized in appropriate devices [62, 66, 67]. Conductivity will change simultaneously and may be used to switch the area between source and drain in a transistor-like structure [68]. 

It has been proposed to modify the redox state of PEDOT to tune the hole injection properties of PEDOT in polymeric LEDs and organic photovoltaic cells [69-72]. However, in most cases the effort associated with tuning the oxidation state results in additional processing expense and therefore PEDOT is preferred in the pristine state. 

Undoped, neutral PEDOT has been made by organometallic means, but differs from a truly undoped, linear PEDOT in its insolubility [61] or its residual halogen end groups [73, 74], 

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