made by

EXAFS Spectroscopy Laboratory
Institute of Solid State Physics (ISSP)

Kengaraga street 8, LV-1063 Riga, Latvia

An Electrochromic Element (ECE) is able to change its optical properties in reversible manner when a voltage is applied across it: the color can be changed from nearly transparent to deep-blue (caused by absorption band at about 1.3 eV).

The ECE maintains the optical properties in the absence of voltage.

The ECE can be used for Smart Windows (Variable Transmittance Devices) and Variable Reflectance Mirrors.

Principal Scheme

A       

Glass Support

B       

Transparent Conductor

C       

Ion Storage Film

D       

Ion Conductor (Electrolyte)

E       

Electrochromic Film

 

CE    

Counter Electrode

WE    

Working Electrode

Real Implementation

A       

Glass Support

B       

Transparent Conductor

C       

Ion Storage Film

D       

Ion Conductor (Electrolyte)

E       

Electrochromic Film

 

CE    

Counter Electrode

WE    

Working Electrode

We use:^*

  ITO (In₂O₃:SnO₂) or SnO₂ as Transparent Conductor

  IrO_x as Ion Storage Film

  WO₃ as Electrochromic Film

  Propylene Carbonate (PC) + 1M LiClO₄ + 1% Acrylic Acid as Liquid Electrolyte

Coloration



The ECE can be colored by applying negative potential (-2.4 < U < 0 V) to the working electrode (WE) for a time t < 60 sec.

Bleaching



The ECE can be bleached by applying positive potential (0 < U < +1.5 V) to the working electrode (WE) for a time t < 60 sec.

The color intensity depends on (i) the value of the potential U and (ii) the time t. The ECE maintains the color after removing the potential for a long period of time (up to several days and more).

N.B. Applied potential is measured versus Counter Electrode !

Maximum Bleaching/Coloration Time	< 60 sec (usually about 10-20 sec)
Working Potential	from -2.4 V (coloration) to +1.5 V (bleaching)
Working Temperature (tested)	from 13 to 25 °C
Working area	about 50 mm x 50 mm
Thickness	< 10 mm