The presentation shows how plastic electronics technology works.

1.
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Plastic
Logic
Technology
Overview
Beginnings
Over
the
last
three
decades
organic
electronics,
which
is
electronics
based
on
carbon
rather
than
silicon,
has
been
extensively
researched.
In
1998
Professor
Richard
Friend’s
group
at
the
University
of
Cambridge,
UK
published
a
seminal
work
using
an
organic
transistor
to
drive
an
organic
light
emitting
diode1.
Two
years
later
Plastic
Logic
was
founded
to
develop
and
commercialize
the
successes
of
the
work
done
by
Professor
Friend,
Professor
Henning
Sirringhaus
and
their
teams
at
the
Cavendish
Laboratory.
Plastic
Logic
soon
focused
its
activity
on
transistor
arrays
for
displays.
Organic
materials
are
typically
flexible,
lightweight
and
robust.
Plastic
Logic
decided
to
exploit
these
attributes
by
developing
its
arrays
on
a
plastic
base
which
would
then
allow
any
final
display
to
be
lighter
and
more
robust
than
equivalent
silicon-­‐based
products.
At
the
same
time,
teams
of
researchers
began
pushing
for
high-­‐quality
materials
that
would
meet
the
rigorous
demands
of
a
commercial
environment.
Several
leading
materials
companies
started
to
put
serious
effort
into
refining
their
materials
for
use
in
this
new
application
space
and
Plastic
Logic
developed
close
relationships
with
many
industrial
research
teams
to
guide
their
work
and
exploit
the
results
at
the
earliest
opportunity.
By
mid-­‐2004
Plastic
Logic
had
developed
small
area
displays
with
relatively
low
resolution
which
were
extremely
robust,
as
evidenced
by
the
photographs
in
Figure
1
a
.
Figure
1
b:
Demonstrating
the
robustness
of
Plastic
Logic’s
displays
–
note
the
small
bend
radius
Just
over
a
year
later,
in
late
2005,
the
company
had
progressed
its
technology
to
large
area
displays
with
much
higher
resolution
as
shown
in
Figure
2.
1
Sirringhaus
et
al,
Science
(1998)
Vol
280
page
1741-­‐1744
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Figure
2:
An
example
of
Plastic
Logic’s
displays
in
late
2005
By
early
2007,
Plastic
Logic
had
identified
a
site
for
its
manufacturing
facility
in
Dresden,
Germany
and
had
begun
the
factory
build.
Ideally
placed
in
the
heart
of
Silicon
Saxony,
Plastic
Logic
has
drawn
a
high-­‐caliber
team
with
extensive
manufacturing
experience
from
the
surrounding
region,
where
many
silicon
manufacturing
facilities
are
based.
The
teams
in
Dresden
and
Cambridge
worked
closely
together
to
ensure
that
the
transfer
of
the
technology
from
lab
to
fab
would
be
as
smooth
and
as
efficient
as
possible.
Only
eighteen
months
later
the
Dresden
manufacturing
facility
opened
its
doors
and
began
producing
flexible
displays
on
a
scale
never
seen
previously
in
the
organic
electronics
community.
a)
b)
Figure
3:
a)
Aerial
image
of
Plastic
Logic’s
manufacturing
facility
in
Dresden
Germany
and
b)
showing
the
size
of
the
motherplates
used
in
the
factory.
In
parallel
the
company
has
been
ramping
its
product
development,
marketing,
and
business
development
and
activities
in
the
US
to
ultimately
complete
the
transition
of
Plastic
Logic
from
a
small
R&D
company,
spun
out
of
academia,
to
a
product-­‐based
organization
with
the
facilities
and
know-­‐how
to
take
technologies
from
the
lab
bench
to
mass
market.
An
Introduction
to
Plastic
Logic
Technology
Now
that
the
field
of
organic
electronics
is
firmly
on
its
journey
to
industrial
maturity
it
is
important
to
step
back
and
recognize
the
key
components
in
taking
a
small
scale,
academic
activity
and
scaling
it
to
the
realities
of
a
commercial
environment.
A
balance
between
device
performance
and
ease
of
manufacture
must
be
struck
for
commercial
success.
For
the
past
10
years,
Plastic
Logic
has
been
at
the
forefront
of
this
progression—
taking
its
own
organic
transistor
technology
from
a
lab
bench
to
a
high
tech
manufacturing
environment—
and
is
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3.
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therefore
well
placed
to
discuss
the
considerations
from
both
the
research
and
manufacturing
perspectives.
This
document
will
give
an
overview
of
the
key
considerations
which
frame
the
transistor’s
performance
and
manufacturing
considerations
based
on
Plastic
Logic’s
learnings.
Transistors
Transistors
are
formed
from
three
electrodes,
a
dialectric
and
a
semiconductor.
The
electrodes
control
the
current
flow
by
way
of
the
voltage
applied
to
them.
The
semiconductor
is
the
material
through
which
the
current
flows.
A
schematic
is
shown
in
Figure
4.
Figure
4:
A
generic
top-­‐gate
transistor
in
cross-­‐section.
A
good
transistor
is
analogous
to
a
good
water
tap.
1) When
you
turn
the
tap
on,
water
soon
starts
to
flow
and
as
you
turn
it
on
a
little
more
the
water
flows
faster
until
it
is
soon
flowing
very
fast.
Similarly
for
a
transistor,
the
current,
which
is
a
flow
of
electric
charge,
should
begin
to
flow
once
a
small
voltage
is
applied
and
as
you
increase
the
voltage
the
current
should
increase
until
you
have
a
surfeit
of
current
for
your
application.
2) When
you
turn
the
tap
off,
it
shouldn’t
allow
any
water
to
leak
out.
Similarly
a
transistor
should
not
allow
current
to
flow
when
it
is
off.
In
the
vast
majority
of
display
applications
the
transistors
use
silicon
as
the
semiconductor
because
it
is
a
well-­‐established
technology
that
can
provide
ample
current
to
drive
the
LCD,
OLED,
electrophoretic
or
whichever
other
screen
technology
is
being
used.
However,
silicon
has
its
drawbacks
in
terms
of
cost,
ease
of
device
manufacture
and
fragility.
In
these
areas
organic
electronics
offer
an
advantage.
Made
primarily
from
materials
which
can
be
processed
from
solution,
the
transistors
are
inherently
simpler
and
cheaper
to
manufacture.
Even
though
today
silicon
can
have
higher
performance
than
organic
semiconductors,
there
are
many
applications
where
the
performance
advantage
of
silicon
is
not
required
and
where
an
organic
electronics
solution
is
more
cost
effective.
The
key
metric
of
semiconductor
performance
is
mobility.
This
is
effectively
a
measure
of
the
speed
at
which
the
charge
can
flow
in
the
semiconductor.
The
required
mobility
is
dependent
on
the
application.
The
faster
the
application,
the
higher
the
mobility
needed.
For
a
television,
the
picture
changes
rapidly
and
hence
the
mobility
required
is
high.
Where
the
image
changes
more
slowly,
such
as
in
an
e-­‐reader,
the
mobility
can
be
much
lower.
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The
typical
mobility
of
crystalline
silicon
is
on
the
order
of
1000cm2/Vs
but
many
applications
use
poly-­‐crystalline
silicon
(mobility
>50cm2/Vs
)
or
amorphous
silicon
(mobility
~0.5cm2/Vs)
as
the
performance
is
still
adequate
but
the
cost
of
manufacture
is
greatly
reduced.
Within
organic
transistors
there
is
also
a
mobility
range
available.
Pentacene,
which
is
a
crystalline
material,
can
achieve
mobilities
of
10cm2/Vs
but
it
is
difficult
to
process
on
any
meaningful
scale.
At
the
other
end
of
the
spectrum,
fully
amorphous
polymer
devices
are
simple
to
manufacture.
They
can
be
made
and
driven
in
air,
without
encapsulation,
and
have
a
whole
host
of
attributes
which
are
extremely
desirable
in
a
manufacturing
context,
but
they
can
only
reach
mobilities
of
around
0.05cm2/Vs.
Nevertheless
this
is
still
sufficient
for
a
number
of
applications.
For
example,
electrophoretic
displays,
which
are
used
to
make
e-­‐paper
and
use
reflected
light
rather
than
an
internal
backlight,
can
be
successfully
driven
with
mobilities
in
this
range.
The
mobility
values
of
various
semiconductors
are
summarised
in
Figure
5.
Source:
A.
Salleo
Figure
5:
Mobility
levels
of
various
semiconductors.
Much
is
made
in
the
academic
literature
about
high
mobility
devices
and
often
this
is
the
metric
which
denotes
whether
or
not
a
device
is
a
success.
However,
the
highest
mobility
devices
are
often
made
in
nitrogen
environments
using
toxic
or
expensive
solvents
and
using
processes
which
are
slow
and
inherently
small
scale.
Such
devices
are
of
no
use
in
commercial
products.
Consistent
devices
are
needed,
made
from
materials
which
are
easy
to
manufacture
on
a
large
scale,
at
a
sensible
cost,
with
good
reproducibility
and
which
are
easy
to
process
in
air.
This
is
often
forgotten
in
the
quest
for
headline
mobility
values.
Fortunately,
over
the
last
few
years
there
has
been
increasing
effort
on
parameters
other
than
mobility.
Now
that
materials
manufacturers
are
becoming
more
acclimated
with
industrial
requirements,
materials
are
starting
to
appear
which
are
closer
to
pentacene
in
performance
whilst
retaining
many
of
the
desirable
processing
attributes
of
the
amorphous
materials.
This
development
will
open
up
display
applications
beyond
electrophoretic
into
LCD
and
OLED
displays.
Additionally
this
advancement
will
enable
organic
electronics
use
in
a
number
of
non-­‐display
applications
such
as
logic.
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Mobility
isn’t
the
only
factor
which
determines
the
current
that
is
available.
The
size
of
the
transistor
is
also
important.
If
the
transistor
is
large
enough
then
a
high
current
can
be
achieved
even
with
a
low
mobility.
In
practice,
the
space
available
for
the
transistor
is
usually
limited.
For
example,
a
laptop
screen
is
backlit
and
the
light
must
pass
through
the
transistor
array
to
the
user.
The
transistor
is
not
transmissive
and
hence
needs
to
be
as
small
as
possible
if
the
front-­‐of-­‐screen
performance
is
not
to
be
impaired.
In
an
electrophoretic
application,
where
reflected
light
is
used,
the
size
of
the
transistor
will
not
affect
the
user
experience
and
this
substantially
relaxes
the
size
constraint,
allowing
the
devices
to
be
much
larger
and
consequently
allowing
the
transistor
mobility
to
be
much
lower.
There
are
still
limits
however.
For
example,
in
active
matrix
displays
at
least
one
transistor
is
required
to
drive
each
pixel.
Therefore,
in
a
display
with
a
resolution
of
200
pixels
per
inch
all
of
the
requirements
for
the
pixel
need
to
fit
within
a
space
127
µm
x
127
µm
in
size.
In
an
ideal
transistor
the
current
would
begin
to
flow
once
a
small
voltage
has
been
applied
to
the
device
to
turn
it
on.
Usually,
however,
there
is
a
resistance
preventing
current
flow
when
the
voltage
begins
to
be
applied.
This
resistance
is
caused
by
poor
physical
or
electrical
contact
between
the
semiconductor
and
the
electrode,
known
as
contact
resistance,
and/or
by
the
bulk
of
the
semiconductor
hindering
the
charge
as
it
travels
to
the
semiconductor/dielectric
interface
where
the
charge
flow
occurs.
In
order
for
current
to
flow
the
voltage
must
be
increased
to
overcome
the
resistance.
The
size
of
the
resistance
is
especially
important
in
mobile
applications
because
the
greater
the
voltage
that
is
required
to
obtain
a
useful
current,
the
quicker
the
battery
will
run
down.
It
is
therefore
desirable
to
minimize
any
resistance
as
far
as
possible,
by
appropriate
choice
of
materials
and
careful
consideration
of
the
cleaning
methods
and
device
processing
methods
employed.
It
is
also
wasteful
if
a
high
voltage
is
needed
to
turn
the
transistor
off
as
this
also
requires
power
which
will
shorten
the
battery
run
time.
Thus
it
is
preferred
if
the
transistor
is
off
with
no
significant
current
flow
when
no
voltages
are
applied.
Additionally,
a
high
current
flow
with
only
minimal
voltage
increase
is
optimum
so
the
device
should
switch
from
off
to
on
with
only
a
small
applied
voltage.
The
materials
choice
for
each
of
the
components
of
the
transistor
(source,
drain,
gate,
semiconductor
and
dielectric)
can
have
significant
implications
for
its
performance
and
the
relative
ease
that
charge
can
flow.
The
source
and
drain
electrodes
must
be
chosen
so
that
charge
can
flow
easily
from
the
source
through
the
semiconductor
to
the
drain
when
the
transistor
is
on.
The
dielectric
must
also
be
carefully
chosen
as
the
wrong
dielectric
can
reduce
the
device
mobility
by
several
orders
of
magnitude
which
would
render
the
device
worthless.
Plastic
Logic
has
long
realized
the
importance
of
the
dielectric
choice
and
has
extensive
experience
in
matching
the
dielectric
to
the
semiconductor.
Materials
suppliers
are
now
also
seriously
investigating
the
dielectric
selection
to
provide
the
combination
of
dielectric
and
semiconductor
to
device
companies
rather
than
just
providing
the
semiconductor,
which
was
previously
the
case.
From
this
discussion
it
is
clear
that,
when
designing
a
transistor
for
the
mass
market,
mobility
is
only
part
of
the
story.
The
ease
at
which
the
device
can
be
turned
on
and
off
is
also
important
and
depends
on
the
choice
of
materials.
However,
there
are
yet
further
considerations
when
the
leap
is
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6.
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made
from
the
individual
transistor
to
the
active
matrix
array
for
a
display
application.
For
example,
in
arrays,
device
uniformity
is
key.
It
is
expected
that
devices
will
perform
similarly
to
one
another,
otherwise
visual
differences
may
be
observable
in
the
resultant
display.
Operational
stability
is
also
required
so
that
the
array
continues
to
function
predictably
throughout
its
life,
with
all
of
the
individual
devices
aging
consistently
regardless
of
how
they
have
been
driven.
Active
Matrix
Arrays
for
Display
Applications
Active
matrix
arrays
consist
of
a
series
of
transistors
laid
out
in
a
grid.
The
isolated
gate
line
shown
in
Figure
4
is
extended
to
connect
all
transistors
in
the
same
row
and
the
source
line
in
Figure
4
is
extended
to
connect
all
the
transistors
in
the
same
column.
This
allows
each
transistor
to
be
uniquely
addressed.
These
arrays
can
then
be
used
to
drive
display
media,
for
example,
electrophoretic
media
(such
as
E
Ink),
LCD
or
OLED.
In
the
simplest
architecture,
each
pixel
within
the
display
is
controlled
by
one
transistor
and
if
the
transistor
is
switched
on
then
the
pixel
will
switch
and
otherwise
will
not
switch.
A
schematic
is
shown
in
Figure
6a
with
the
display
pixels
overlaid
in
Figure
6b.
a)
b)
Figure
6:
a)
A
transistor
array
and
b)
Display
pixels
overlaying
the
transistor
array
Voltage
is
applied
to
the
first
gate
line
and
concurrently
each
source
line
in
parallel,
this
is
then
repeated
with
the
second
gate
line
and
so
on
until
all
the
transistors
have
been
addressed
and
all
the
pixels
are
on
or
off
as
required
for
the
image.
Because
the
millions
of
transistors
within
the
array
are
addressed
one
row
at
a
time,
any
one
transistor
is
only
addressed
for
a
very
short
period.
In
the
example
in
Figure
6b,
voltages
are
applied
to
turn
on
the
TFT
at
the
Source-­‐2
Gate-­‐2
intersection
(S2G2)
and
change
the
associated
pixel
to
its
on
state,
which
is
white,
and
then
applied
to
S4G3
and
finally
S2G4
to
change
their
pixel
colors
to
white.
The
remaining
transistors
are
left
in
their
off
state
and
the
pixels
remain
black.
LCD
color
displays
use
this
basic
principle
and
then
use
color
filters
distributed
in
a
pattern
across
the
display
to
give
red,
green
and
blue
pixels
as
well
as
white
ones.
This
methodology
can
also
be
used
for
reflective
technologies
although
there
are
also
other
device
architectures
that
can
be
employed.
The
gate
lines
and
source
lines
running
across
and
down
the
transistor
array
can
form
transistors
other
than
those
in
the
array
if
the
array
is
poorly
constructed.
These
unwanted
transistors,
called
parasitics,
can
cause
the
display
pixels
to
turn
on
when
they
should
be
off.
It
is
important
that
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7.
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careful
consideration
is
given
to
where
connections
are
routed
and
how
the
devices
are
built
up
so
that
parasitic
devices
are
avoided.
Plastic
Logic
has
extensive
knowledge
in
array
design
to
minimize
the
impact
of
parasitic
devices.
Parasitic
transistors
are
not
the
only
source
of
unwanted
current.
Transistors
within
the
array
can
also
leak
current
to
one
another
so
it
is
important
to
ensure
there
is
no
path
for
the
current
to
travel
between
neighboring
devices.
While
we
have
focused
on
transistors,
these
are
not
the
only
devices
within
the
array
and
the
other
components
must
not
be
neglected.
During
the
time
that
the
transistor
is
not
being
addressed
the
charge
it
produced
during
the
address
time
needs
to
be
retained
until
it
is
next
addressed.
This
is
achieved
by
the
use
of
a
storage
capacitor
which
comprises
two
plates
separated
by
a
dielectric.
The
drain
pad
of
the
transistor
makes
up
one
of
the
plates
of
the
capacitor.
The
cross-­‐section
is
shown
in
Figure
7.
Figure
7:
Cross-­‐section
of
TFT
and
capacitor
combination
The
metric
for
the
capacitor
is
known
as
capacitance.
The
capacitance
is
a
measure
of
the
ability
of
the
capacitor
to
store
charge
and
is
determined
by
the
capacitor’s
area,
the
separation
of
the
plates,
and
a
measure
of
the
dielectric
known
as
the
dielectric
constant.
For
any
given
capacitance
the
area
of
the
capacitor
can
be
reduced
if
the
dielectric
constant
is
increased.
As
space
is
at
a
premium
within
the
array
it
would
be
ideal
to
have
a
dielectric
with
a
high
dielectric
constant
so
that
the
capacitor
can
be
as
small
as
possible.
Unfortunately
most
organic
transistors
have
relatively
small
dielectric
constants,
when
compared
to
inorganic
transistors,
and
consequently
the
capacitor
structure
is
often
larger
than
would
ideally
be
the
case.
The
competing
requirements
of
the
transistor
and
the
capacitor
present
one
of
the
problems
that
has
to
be
addressed
for
success
in
the
displays
market.
There
are
several
routes
to
solve
the
problem,
all
of
which
present
challenges.
1) The
transistor
could
be
shrunk
to
allow
more
space
for
the
capacitor,
although
this
will
increase
the
mobility
requirement.
2) The
dielectric
used
could
have
a
high
dielectric
constant
so
that
the
capacitor
can
be
small,
but
this
will
impair
transistor
performance.
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8.
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3) A
capacitor
and
the
transistor
could
be
processed
such
that
they
use
different
dielectrics
from
one
another,
although
this
will
certainly
add
complexity
and
consequently
cost
to
the
system.
As
was
previously
stated,
materials
suppliers
have
recently
started
to
realize
that
the
dielectric
must
also
be
carefully
optimized
to
match
the
semiconductor
and
in
so
doing
maximize
the
transistor
mobility.
Materials
manufacturers
also
need
to
extend
this
thinking
and
realize
that
the
transistor
is
not
the
only
component
in
the
array
and
that
developing
a
semiconductor
that
could
work
with
high
dielectric
constant
materials
would
be
very
desirable.
The
array
structure
is
complicated
further
because
the
bottom
capacitor
plate
(the
drain
pad)
needs
to
be
in
direct
contact
with
the
display
media.
As
shown
in
Figure
7,
the
drain
pad
is
underneath
all
of
the
other
layers
so
it
therefore
has
to
be
brought
to
the
top
of
the
stack.
This
is
achieved
by
adding
an
interlayer
dielectric,
making
a
hole
in
the
stack
of
layers
and
adding
a
metal
or
polymeric
conductor
on
top
to
effectively
move
the
bottom
capacitor
plate
from
the
bottom
of
the
stack
to
the
top.
A
generic
repeat
unit
in
the
active
matrix
array
would
therefore
be:
a)
b)
Figure
8:
a)
Plan
view
of
a
generic
repeat
unit
in
an
active
matrix
array,
b)
cross-­‐section
of
repeat
unit.
Thus
once
the
transistors
are
incorporated
into
a
real-­‐world
application
there
are
many
aspects
which
must
be
considered
and
not
just
the
design
and
performance
of
the
transistor
itself.
This
is
true
not
only
in
displays
but
also
in
non-­‐display
applications
such
as
sensors
or
RFID.
Non-­‐Display
Applications
Transistors
can
either
be
p-­‐type
or
n-­‐type
depending
on
whether
they
are
turned
on
by
applying
negative
voltages
or
positive
ones.
For
display
applications
an
active
matrix
array
can
be
produced
using
transistors
which
are
either
all
p-­‐type
or
all
n-­‐type.
Logic
circuits,
however,
are
most
efficient
if
both
n-­‐type
and
p-­‐type
transistors
are
available.
To
date
the
vast
majority
of
organic
transistors
are
p-­‐type
because
p-­‐type
semiconductors
are
the
most
advanced
in
terms
of
our
understanding
and
also
in
terms
of
the
key
performance
metrics
such
as
mobility.
However
n-­‐type
transistors
would
bring
many
advantages
even
into
the
displays
space.
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9.
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A
display
requires
drivers
in
order
to
address
the
pixels
correctly
and
in
Plastic
Logic’s
case
all
of
the
driving
electronics
which
surround
the
active
matrix
array
are
made
from
silicon.
Some
of
this
could
be
replaced
by
organic
transistors
if
both
p
and
n-­‐type
materials
were
available.
This
would
allow
the
advantages
of
organic
materials,
namely
ease
of
processing,
cost
and
robustness
to
be
utilized
in
more
of
the
system.
Some
companies
are
beginning
to
seriously
develop
n-­‐type
materials
and
Plastic
Logic
is
actively
engaged
in
the
testing
and
development
of
these
materials
to
ensure
they
reach
commercial
viability
as
soon
as
is
practicable.
In
addition
to
n-­‐type
devices,
Plastic
Logic
has
also
given
significant
consideration
into
how
the
devices
are
constructed
so
that
unwanted
capacitances
and
currents
can
be
removed.
Plastic
Logic’s
IP
portfolio
extends
broadly
over
high-­‐resolution
printing
methods,
where
sub-­‐micron
channel
lengths
have
been
demonstrated,
and
fine-­‐feature
patterning
techniques,
both
of
which
help
to
reduce
parasitics
and
improve
the
device
speed.
As
the
transistor
mobility
improves
for
commercially
viable
devices
in
both
p
and
n-­‐type
devices,
and
deposition
methods
enable
fine
features
and
low
parasitics,
it
becomes
possible
for
organic
electronics
to
move
into
other
application
areas
such
as
RFID,
Sensors,
ASIC,
and
smartcards.
Reliability
Of
paramount
importance
when
discussing
any
commercial
application
is
the
reliability
of
the
electronic
components
in
the
product
and
the
reliability
of
the
process
used
to
make
them.
The
product
will
not
be
a
commercial
success
if
the
transistors
stop
working
when
they
are
exposed
to
heat,
light,
water,
or
wear
out
after
being
operated
for
a
few
weeks.
In
the
case
of
displays
this
would
create
‘dead’
pixels
which
remain
permanently
off
and
in
logic
circuits
it
would
prevent
the
circuit
from
operating
correctly
and
cause
the
product
to
fail.
While
it
would
be
desirable
for
the
transistors
to
always
perform
the
same
way
in
all
environments
and
all
operating
conditions
this
is
unrealistic.
Temperature
and
moisture
will
change
the
device
behaviour
not
only
in
organic
devices
but
in
silicon
and
other
semiconductors
too.
Additionally,
as
with
most
things,
extensive
use
will
cause
degradation
over
time.
When
designing
a
product
it
is
important
to
investigate
the
operation
of
the
devices
in
a
range
of
environments
and
under
a
range
of
operating
conditions
which
are
specific
to
the
application
in
question.
The
changes
to
the
device
performance
caused
by
varying
these
factors
can
then
be
accounted
for
in
the
design
of
the
devices
such
that
it
doesn’t
cause
a
difference
in
the
visual
performance
of
the
display
or
the
operation
of
the
logic
circuit.
When
completing
such
a
design
it
is
important
to
remember
that
it
is
the
performance
of
the
worst
transistor
that
is
of
most
interest.
The
worst
transistor
in
the
display
must
still
be
functional
at
the
end
of
the
product
life
and
therefore
the
worst
transistor
dictates
the
pixel
design.
If
the
product
is
to
reach
its
full
potential
and
thereby
maximize
revenue
for
the
manufacturer,
uniformity
across
all
the
devices
within
the
display
is
key.
The
importance
of
uniformity
is
also
clear
when
considering
how
the
products
will
be
tested
to
ensure
they
are
fit
for
purpose.
It
is
impossible
to
fully
test
every
device
in
every
product
and
therefore
it
is
important
that
the
transistor
behaviour
is
consistent
and
predictable
such
that
a
basic
test
will
show
whether
the
product
will
work
as
expected.
Again
this
highlights
the
importance
of
using
materials
which
can
be
easily
mass-­‐produced
and
are
well
understood
so
that
the
variability
between
devices
is
minimized.
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10.
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It
is
not
only
variability
in
the
materials
which
can
cause
variation
in
the
device
performance.
Variability
in
the
process
can
have
the
same
effect
and
hence
the
manufacturing
process
needs
to
be
robust
and
repeatable.
An
unreliable
process
will
reduce
yield,
increase
cost
and
make
forecasting
product
availability
difficult.
This
needs
to
be
considered
at
the
outset,
in
the
initial
device
design,
as
a
complicated
and
intricate
process
will
be
harder
to
maintain
than
a
straightforward
and
simple
one.
Manufacturing
The
requirements
and
intricacies
of
manufacturing
are
worthy
of
a
document
in
their
own
right.
Here,
a
couple
of
examples
are
used
to
give
a
flavor
of
some
of
the
considerations
involved
in
the
transition
from
a
lab-­‐based
environment
to
a
manufacturing
one.
When
moving
from
an
R&D
environment
to
manufacturing
every
minutia
has
to
be
validated
and
understood.
Issues
that
affect
a
couple
of
displays
in
the
lab
could
wipe
out
whole
batches
of
displays
in
a
factory,
which
would
be
extremely
costly.
Thus
it
is
important
to
understand
all
the
parameters
so
that
issues
can
be
rectified
quickly
with
minimal
impact
on
production.
As
an
example,
one
major
consideration
is
display
build
time.
In
a
lab,
where
displays
are
being
processed
one
at
a
time,
tight
time
constraints
can
be
accommodated.
For
example,
if
one
layer
cannot
be
exposed
to
air
for
more
than
an
hour
or
one
clean
or
treatment
process
wears
off
after
ten
minutes,
then
displays
can
be
moved
from
one
station
to
another
quickly
in
order
to
accommodate
this
criterion.
In
a
manufacturing
facility
however,
such
tight
time
constraints
cause
complexity
because
displays
are
usually
processed
in
relatively
large
batches
using
automated
equipment,
meaning
that
any
one
display
must
wait
for
all
the
other
displays
ahead
of
it
before
it
goes
through
a
particular
process.
Any
delay
could
potentially
push
large
numbers
of
displays
beyond
the
allowable
time
between
process
steps.
Consequently
any
time
criticalities
need
to
be
fully
understood,
not
only
so
batches
are
processed
through
genuinely
critical
steps
within
the
allotted
time
but
also
so
perfectly
good
batches
are
not
scrapped
for
failing
to
meet
an
arbitrary
time
constraint.
A
second
issue
in
moving
from
the
lab
to
manufacturing
is
how
to
scale
the
processing
of
flexible
substrates
to
a
size
not
previously
used
in
industry.
The
manufacturing
of
organic
electronic
devices
on
flexible
substrates
is
still
in
its
infancy.
Equipment
suppliers
are
used
to
sheet
fed,
glass
based
products
and
their
tools
are
designed
with
rigid,
inflexible
substrates
in
mind.
Plastic
Logic
addressed
this
conundrum
by
laminating
its
flexible
substrate
to
glass
so
that
it
could
be
processed
as
if
it
were
glass.
This
minimized
the
equipment
modifications,
and
removed
the
challenge
from
each
and
every
tool
supplier,
who
might
each
have
different,
and
potentially
mutually
exclusive,
ways
of
addressing
the
issue,
and
moved
it
squarely
back
to
Plastic
Logic.
This
allowed
Plastic
Logic
to
develop
unrivalled
expertise
and
competency
in
the
handling
and
processing
of
flexible
substrates
and
their
lamination
to
glass
and
facilitated
a
deep
understanding
of
how
the
substrate
is
affected
by
factors
such
as
temperature,
chemicals
and
humidity,
which
is
invaluable
information
not
only
at
the
lamination
stages
but
for
all
of
the
other
processing
steps.These
examples
help
to
show
that
to
successfully
progress
out
of
the
lab
and
into
a
factory
there
are
not
only
scientific
considerations,
such
as
how
the
transistor
degrades
or
whether
devices
are
uniform,
but
also
practical
considerations,
which
are
every
bit
as
important
and
which
must
also
be
addressed.
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11.
WHITE
PAPER
Conclusion
In
a
commercial
environment
it
is
not
enough
to
design
a
transistor
purely
on
the
basis
of
high
mobility.
The
optimum
transistor
is
the
one
which
can
be
processed
simply,
affordably,
consistently,
and
which
has
a
performance
that
is
sufficient
for
the
task
in
hand.
Additionally
the
requirements
of
the
other
components
of
the
system,
for
example
the
capacitor
in
the
display,
must
also
be
accounted
for
right
at
the
outset
of
the
design.
This
ensures
that
the
design
optimizes
the
system
rather
than
any
individual
component.
In
designing
a
system,
Plastic
Logic
understands
the
balance
that
must
be
struck
between
the
myriad
of
influencing
factors,
and
this
is
critical
to
commercial
success.
Plastic
Logic
has
unrivalled
expertise
in
developing
organic
electronics
for
consumer
products
and
in
such
a
rapidly
changing
technology
environment
it
is
vital
to
remain
at
the
forefront
of
research
and
development
for
early
integration
of
new
features
and
hence
is
a
competitive
advantage.
Plastic
Logic
is
devoting
significant
resources
to
the
integration
of
a
compatible
color
technology
and
optimum
front-­‐of-­‐screen
performance.
Plastic
Logic
is
also
focused
on
the
continued
development
of
the
p-­‐type
transistors
in
its
array,
using
materials
with
similar
performance
to
amorphous
silicon.
For
further
cost
benefit
and
feature
enhancement
it
is
also
developing
n-­‐type
transistors
which
will,
when
integrated
successfully,
expand
the
functionality
of
organic
electronics
beyond
the
transistor
array
and
into
the
surrounding
logic
circuits.
In
Plastic
Logic
the
research
teams
are
highly
aligned
with
the
manufacturing
engineers
to
procure
suitable
equipment
that
can
meet
the
challenges
of
mass
manufacture,
both
in
Dresden
and
in
Plastic
Logic’s
planned
second
manufacturing
facility
in
Russia.
Close
alignment
ensures
rapid
inclusion
of
new
advances
into
the
end
product.
This
work
will
ensure
that
Plastic
Logic
continues
to
advance
its
technology
platform
for
the
future.
Plastic Logic Inc. Headquarters 650 Castro Street, Suite 500 Mountain View, CA 94041
USA Phone: +1 (650) 584-2100 Fax: +1 (650) 584-2101
© 2011
PLASTIC
LOGIC.
ALL
RIGHTS
RESERVED.
THIS
DOCUMENT
IS
PLASTIC
LOGIC
PUBLIC
INFORMATION
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