<s>
A	O
flexible	B-Algorithm
organic	I-Algorithm
light-emitting	I-Algorithm
diode	I-Algorithm
(	O
FOLED	B-Algorithm
)	O
is	O
a	O
type	O
of	O
organic	B-Device
light-emitting	I-Device
diode	I-Device
(	O
OLED	B-Device
)	O
incorporating	O
a	O
flexible	O
plastic	O
substrate	B-Architecture
on	O
which	O
the	O
electroluminescent	O
organic	B-Algorithm
semiconductor	I-Algorithm
is	O
deposited	O
.	O
</s>
<s>
Currently	O
the	O
focus	O
of	O
research	O
in	O
industrial	O
and	O
academic	O
groups	O
,	O
flexible	B-Algorithm
OLEDs	I-Algorithm
form	O
one	O
method	O
of	O
fabricating	O
a	O
rollable	B-Application
display	I-Application
.	O
</s>
<s>
An	O
OLED	B-Device
emits	O
light	O
due	O
to	O
the	O
electroluminescence	O
of	O
thin	O
films	O
of	O
organic	B-Algorithm
semiconductors	I-Algorithm
approximately	O
100nm	O
thick	O
.	O
</s>
<s>
Regular	O
OLEDs	B-Device
are	O
usually	O
fabricated	O
on	O
a	O
glass	O
substrate	B-Architecture
,	O
but	O
by	O
replacing	O
glass	O
with	O
a	O
flexible	O
plastic	O
such	O
as	O
polyethylene	O
terephthalate	O
(	O
PET	O
)	O
among	O
others	O
,	O
OLEDs	B-Device
can	O
be	O
made	O
both	O
bendable	O
and	O
lightweight	O
.	O
</s>
<s>
In	O
contrast	O
,	O
flexible	B-Algorithm
OLED	I-Algorithm
devices	O
can	O
be	O
fabricated	O
by	O
deposition	O
of	O
the	O
organic	O
layer	O
onto	O
the	O
substrate	B-Architecture
using	O
a	O
method	O
derived	O
from	O
inkjet	O
printing	O
,	O
allowing	O
the	O
inexpensive	O
and	O
roll-to-roll	O
fabrication	O
of	O
printed	O
electronics	O
.	O
</s>
<s>
Flexible	B-Algorithm
OLEDs	I-Algorithm
may	O
be	O
used	O
in	O
the	O
production	O
of	O
rollable	B-Application
displays	I-Application
,	O
electronic	O
paper	O
,	O
or	O
bendable	O
displays	O
which	O
can	O
be	O
integrated	O
into	O
clothing	O
,	O
wallpaper	O
or	O
other	O
curved	O
surfaces	O
.	O
</s>
<s>
Both	O
flexible	O
substrate	B-Architecture
itself	O
as	O
well	O
as	O
the	O
process	O
of	O
bending	O
the	O
device	O
introduce	O
stress	O
into	O
the	O
materials	O
.	O
</s>
<s>
There	O
may	O
be	O
residual	O
stress	O
from	O
the	O
deposition	O
of	O
layers	O
onto	O
a	O
flexible	O
substrate	B-Architecture
,	O
thermal	O
stresses	O
due	O
to	O
the	O
different	O
coefficient	O
of	O
thermal	O
expansion	O
of	O
materials	O
in	O
the	O
device	O
,	O
in	O
addition	O
to	O
the	O
external	O
stress	O
from	O
the	O
bending	O
of	O
the	O
device	O
.	O
</s>
<s>
Fracture	O
of	O
the	O
anode	O
can	O
occur	O
which	O
can	O
increase	O
the	O
sheet	O
resistance	O
of	O
the	O
ITO	O
or	O
disrupt	O
the	O
layered	O
structure	O
of	O
the	O
OLED	B-Device
.	O
</s>
<s>
Although	O
ITO	O
is	O
the	O
most	O
common	O
and	O
best	O
understood	O
anode	O
material	O
used	O
in	O
OLEDs	B-Device
,	O
research	O
has	O
been	O
undertaken	O
into	O
alternative	O
materials	O
that	O
are	O
better	O
suited	O
for	O
flexible	O
applications	O
including	O
carbon	O
nanotubes	O
.	O
</s>
<s>
Encapsulation	O
is	O
another	O
challenge	O
for	O
flexible	B-Algorithm
OLED	I-Algorithm
devices	O
.	O
</s>
<s>
The	O
materials	O
in	O
an	O
OLED	B-Device
are	O
sensitive	O
to	O
air	O
and	O
moisture	O
which	O
lead	O
to	O
degradation	O
of	O
the	O
materials	O
themselves	O
as	O
well	O
as	O
quenching	O
of	O
excited	O
states	O
within	O
the	O
molecule	O
.	O
</s>
<s>
The	O
common	O
method	O
of	O
encapsulation	O
for	O
regular	O
OLEDs	B-Device
is	O
to	O
seal	O
the	O
organic	O
layer	O
between	O
glass	O
.	O
</s>
<s>
Flexible	O
encapsulation	O
methods	O
are	O
generally	O
not	O
as	O
effective	O
a	O
barrier	O
to	O
air	O
and	O
moisture	O
as	O
glass	O
,	O
and	O
current	O
research	O
aims	O
to	O
improve	O
the	O
encapsulation	O
of	O
flexible	O
organic	B-Device
light	I-Device
emitting	I-Device
diodes	I-Device
.	O
</s>
