Norman Ferrer Valls
Iván López Lliberós
Introduction
Organic semiconductors
Electrochromic technologies
• Liquid crystal
• Liquid crystal display
• Viologen
• Viologen + TiO2
• WO3
Electrochromic applications
Conclusions
Introduction Semiconductors form the basis of electronic
devices.
Conventionally semiconductors:
• Silicon
• Germanium
• Selenium
• Aluminium
Great progress with organic and hybrid materials as
semiconductors.
Organic semiconductors
Polymers are naturally insulated.
Through the interaction of alternating single and
double bonds, is created a space between the
valence band and conduction band.
Doping: achieves the
creating of free carrier
Acting either oxidation or reduction
Radical cations or anions are formed
Doping -> Add or remove electrons in the polymer
chain through a redox reaction.
Conjugated polymers with delocalized -electron
systems behave as model organic semiconductors
Organic semiconductors
Examples:
Organic semiconductors
Apps
OSC
OLED
ELECTROCHROMIC
OFET
Organic semiconductors
Electrochromic devices • Is the reversibly ability of a material to change
its colour by an electrochemical oxidation or reduction reaction, caused by the application of an electrical potential.
Electrochromism
●“Thermochromism” and “photochromism” describe
changes of colour produced by heat and light.
Electrochromic devices
●Visible spectrum:
Transmittance (T) Reflectance (R)
Absorptance (A) Emittance (E)
When thin film of electrochromic materials are integrated in devices, it becomes possible to modulate
Electrochromic devices
●Goal -> Achieve different wavelengths associated
to variable potential.
Electrochromic devices
Electrochromic devices
Liquid crystal
Electrochromic devices
Liquid crystal display
Electrochromic devices
The image describes the synthesis
of aelectrochromic ionic liquid
(IL) based on a phosphonium core
tethered to a viologen moiety.
The electrochromic platform
exhibits a coloration efficiency of
10.72 cm2 C−1 and a varied
optical output as a function of the
incident current.
Viologen:
Electrochromic devices ● Viologen display functionalized with TiO2: an
electrochromic display based on an electrolyte
consisting of an aqueous solution of a dipositively
charged organic salt, containing a colourless cation
that undergoes a one-electron reduction process to
produce a purple radical cation, upon application of
a negative potential to the electrode.
Electrochromic devices
The device is made up of 5 layers, whose
composition is:
Plastic or glass
Conductive substrate +
Electrochromic layer
Electrolyte
Conductive substrate + Ion
storage layer
Plastic or glass
Electrochromic devices ●The nature of direct current preserves the relatively
unstable monocationic radical.
●This change in spectral features explains the
prolonged optical memory.
●This effect could be used to make a prolonged
darkened state.
Electrochromic devices
Electrochromic devices WO3 A metal cation ( Li+ normaly ) which intercalates WO3
grid when it is reduced by an applied external
voltage. Positive ions that were stored in the counter
electrode layer , cross the ion conductor layer to reach
the electrochromic material when it receives an
electrical current. This chemical reaction produces
changes in the UV - visible spectrum of WO3.
Electrochromic devices
Some applications…
Smart windows
Welding shields https://www.youtube.com/watch?v=OpZUN3dd51s
Rearview mirrors of
cars
Conclusion
ADVANTAGES DISADVANTAGES
Lifetime (cycles)
Refresh capacity
Technology
developing in
progress
Memory
Little potential for use
Pronounced optical
contrast
Reversibility
Improve the quality of
life of people in
different areas
Is everything clear or are you a little
chromic…?
Thank you!