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Electrolyte for Phthalocyanine Based Electrochromic Displays

IP.com Disclosure Number: IPCOM000050389D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Collins, GCS: AUTHOR

Abstract

It has been observed that when phthalocyanine-based electrochromic displays are cycled through a large number of color changes, the color intensity gradually decreases until it is no longer observable. We have found that this is due to the use of a predominantly aqueous electrolyte, typically a solution of NaCl in water.

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Electrolyte for Phthalocyanine Based Electrochromic Displays

It has been observed that when phthalocyanine-based electrochromic displays are cycled through a large number of color changes, the color intensity gradually decreases until it is no longer observable. We have found that this is due to the use of a predominantly aqueous electrolyte, typically a solution of NaCl in water.

The color loss can be avoided by using as electrolyte a conductivity salt dissolved in a solvent which is predominantly non-aqueous and contains no other source of hydroxyl ions. An example is a solution of NaCl in ethylene glycol with up to 25 percent water.

The use of an NaCl/glycol electrolyte was investigated for three electrochromic phthalocyanines- erbium phthalocyanine, gadolinium phthalocyanine and ytterbium phthalocyanine- and compared with the results using a conventional NaCl-water electrolyte. The phthalocyanines were in the form of thin films several thousand angstroms thick and subjected to rapid potential step cycling from 0 V to + 1,000 mV. In each case substantially improved lifetime was obtained with the NaCl-glycol electrolyte, as indicated below: NaCl-water NaCl-glycol

Er(Pc(2)) 200,000 cycles 1.5 x 10/6/ cycles No color left No color loss observed

Gd(Pc(2)) 175,000 cycles 2 x 10/6/ cycles No color left No color loss observed

Yb(Pc(2)) 400,000 cycles 1.3 x 10/6/ cycles Severe fading No color loss observed.

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