<s>
Electrochromism	B-Algorithm
is	O
a	O
phenomenon	O
in	O
which	O
a	O
material	O
displays	O
changes	O
in	O
color	O
or	O
opacity	O
in	O
response	O
to	O
an	O
electrical	O
stimulus	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
a	O
smart	O
window	O
made	O
of	O
an	O
electrochromic	B-Algorithm
material	O
can	O
block	O
specific	O
wavelengths	O
of	O
ultraviolet	B-Application
,	O
visible	O
or	O
(	O
near	O
)	O
infrared	O
light	O
.	O
</s>
<s>
As	O
the	O
color	O
change	O
is	O
persistent	O
and	O
energy	O
need	O
only	O
be	O
applied	O
to	O
effect	O
a	O
change	O
,	O
electrochromic	B-Algorithm
materials	O
are	O
used	O
to	O
control	O
the	O
amount	O
of	O
light	O
and	O
heat	O
allowed	O
to	O
pass	O
through	O
a	O
surface	O
,	O
most	O
commonly	O
"	O
smart	O
windows	O
"	O
.	O
</s>
<s>
The	O
phenomenon	O
of	O
electrochromism	B-Algorithm
occurs	O
in	O
some	O
transition	O
metal	O
oxides	O
which	O
conduct	O
both	O
electricity	O
and	O
ions	O
,	O
such	O
as	O
tungsten	O
trioxide	O
(	O
WO3	O
)	O
.	O
</s>
<s>
This	O
is	O
a	O
redox	B-Operating_System
reaction	O
,	O
since	O
the	O
electroactive	O
metal	O
is	O
accepting	O
electrons	O
from	O
the	O
electrodes	O
,	O
forming	O
a	O
half-cell	O
.	O
</s>
<s>
Electrochromic	B-Algorithm
materials	O
,	O
also	O
known	O
as	O
chromophores	O
,	O
affect	O
the	O
optical	O
color	O
or	O
opacity	O
of	O
a	O
surface	O
when	O
a	O
voltage	O
is	O
applied	O
.	O
</s>
<s>
Among	O
the	O
metal	O
oxides	O
,	O
tungsten	O
oxide	O
(	O
WO3	O
)	O
is	O
the	O
most	O
extensively	O
studied	O
and	O
well-known	O
electrochromic	B-Algorithm
material	O
.	O
</s>
<s>
Viologens	O
are	O
a	O
class	O
of	O
organic	O
materials	O
that	O
are	O
being	O
intensively	O
investigated	O
for	O
electrochromic	B-Algorithm
applications	O
.	O
</s>
<s>
These	O
4	O
,	O
4′-bipyridine	O
compounds	O
display	O
reversible	O
color	O
changes	O
between	O
a	O
colorless	O
and	O
a	O
deep-blue	O
color	O
due	O
to	O
redox	B-Operating_System
reactions	O
.	O
</s>
<s>
Possible	O
advantages	O
of	O
viologens	O
include	O
their	O
optical	O
contrast	O
,	O
coloration	O
efficiency	O
,	O
redox	B-Operating_System
stability	O
,	O
ease	O
of	O
design	O
and	O
potential	O
to	O
scale	O
up	O
for	O
large-area	O
preparation	O
.	O
</s>
<s>
A	O
variety	O
of	O
conducting	O
polymers	O
are	O
also	O
of	O
interest	O
for	O
displays	O
,	O
including	O
polypyrrole	B-Algorithm
,	O
PEDOT	B-Algorithm
,	O
and	O
polyaniline	B-Algorithm
.	O
</s>
<s>
Many	O
methods	O
have	O
been	O
used	O
to	O
synthesize	O
tungsten	O
oxide	O
,	O
including	O
chemical	B-Algorithm
vapor	I-Algorithm
deposition	I-Algorithm
(	O
CVD	O
)	O
,	O
sputtering	O
,	O
thermal	O
evaporation	O
,	O
spray	B-Algorithm
pyrolysis	I-Algorithm
(	O
from	O
a	O
vapor	O
or	O
sol-gel	O
)	O
,	O
and	O
hydrothermal	O
synthesis	O
(	O
from	O
a	O
liquid	O
)	O
.	O
</s>
<s>
Multiple	O
layers	O
are	O
needed	O
for	O
a	O
functional	O
smart	O
window	O
with	O
electrochromic	B-Algorithm
characteristics	O
.	O
</s>
<s>
The	O
first	O
and	O
last	O
are	O
transparent	O
glass	O
made	O
of	O
silica	O
(	O
)	O
,	O
the	O
two	O
electrodes	O
are	O
needed	O
to	O
apply	O
the	O
voltage	O
,	O
which	O
in	O
turn	O
will	O
push	O
(	O
or	O
pull	O
)	O
ions	O
from	O
the	O
ion	O
storage	O
layer	O
,	O
through	O
the	O
electrolyte	O
into	O
the	O
electrochromic	B-Algorithm
material	O
(	O
or	O
vice	O
versa	O
)	O
.	O
</s>
<s>
Applying	O
a	O
high	O
voltage	O
(	O
4V	O
or	O
more	O
)	O
will	O
push	O
lithium-ions	O
into	O
the	O
electrochromic	B-Algorithm
layer	O
,	O
deactivating	O
the	O
electrochromic	B-Algorithm
material	O
.	O
</s>
<s>
By	O
applying	O
a	O
lower	O
voltage	O
(	O
2.5V	O
for	O
example	O
)	O
the	O
concentration	O
of	O
Li-ions	O
in	O
the	O
electrochromic	B-Algorithm
layer	O
decreases	O
,	O
thus	O
activating	O
(	O
N	O
)	O
IR-active	O
tungsten	O
oxide	O
.	O
</s>
<s>
Depending	O
on	O
the	O
electrochromic	B-Algorithm
material	O
used	O
,	O
different	O
parts	O
of	O
the	O
spectrum	O
can	O
be	O
blocked	O
,	O
this	O
way	O
UV	O
,	O
visible	O
and	O
IR	O
light	O
can	O
be	O
independently	O
reflected	O
at	O
the	O
will	O
of	O
a	O
user	O
.	O
</s>
<s>
Several	O
electrochromic	B-Algorithm
devices	O
have	O
been	O
developed	O
.	O
</s>
<s>
Electrochromism	B-Algorithm
is	O
commonly	O
used	O
in	O
the	O
production	O
of	O
electrochromic	B-Algorithm
windows	O
or	O
"	O
smart	O
glass	O
"	O
,	O
and	O
more	O
recently	O
electrochromic	B-Algorithm
displays	O
on	O
paper	O
substrate	O
as	O
anti-counterfeiting	O
systems	O
integrated	O
into	O
packaging	O
.	O
</s>
<s>
NiO	O
materials	O
have	O
been	O
widely	O
studied	O
as	O
counter	O
electrodes	O
for	O
complementary	O
electrochromic	B-Algorithm
devices	O
,	O
particularly	O
for	O
smart	O
windows	O
.	O
</s>
<s>
ICE	O
3	O
high	O
speed	O
trains	O
use	O
electrochromic	B-Algorithm
glass	O
panels	O
between	O
the	O
passenger	O
compartment	O
and	O
the	O
driver	O
's	O
cabin	O
.	O
</s>
<s>
Electrochromic	B-Algorithm
windows	O
are	O
used	O
in	O
the	O
Boeing	O
787	O
Dreamliner	O
,	O
allowing	O
crew	O
and	O
passengers	O
to	O
control	O
the	O
transparency	O
of	O
the	O
windows	O
and	O
prevent	O
glare	O
.	O
</s>
