16-05-2012, 04:13 PM
Recent Progress in Organic Electronics
[attachment=22176]
Introduction
Organic electronics as a field of study has come a long
way in the past 10 years. From a literature search
covering many of the available R&D materials databases,
and using the search terms “organic thin film
transistor,” 12 publications were found for 1993, but well
over 300 were found for 2003! If the search is broadened
to include organic thin film electronic devices such as
memory, photovoltaics, and organic light-emitting diodes
(OLEDs), over 40,000 publications are found for
the period of 1998-2003. This implies a very active
research subject spanning many areas, including materials
development, device design, deposition processes,
and modeling. More researchers continue to join the
field, with few dropping out each year, even though, as
a community, we still await the key applications that
may drive organic electronics toward mature industrial
persistence.
Semiconductors
Pentacene has continued to be the most widely used
small molecule semiconductor primarily due to routinely
obtainable thin film transistor hole mobilities in excess
of 1 cm2/Vs. Researchers are beginning to investigate
long-term and operational stability in pentacene
devices,4c,12 but pentacene still remains the most reliable
benchmark material for vapor-deposited thin film transistors
(TFTs). Recent reports have increased awareness
that charge carrier mobility is not the only device
parameter to consider, and for some applications, may
not even be the most important. For RFID applications,
mobility and threshold voltage may be critically important,
but for display backplanes, threshold voltage
stability and off current may be the key parameters.13
Many reports have been made using pentacene in thin
film devices,9a,14 but several other materials have also
shown promise, deposited from either the vapor phase
or through solution delivery routes.
Tetracene-Bithiophene
We also report here our latest synthetic effort, tetracene-
bithiophene, and its device performance and
morphology as a function of substrate temperature. A
Stille coupling between 2-chlorotetracene and 5-tributylstannyl-
2,2¢-bithiophene 31 was used to prepare 5-(2-
tetracenyl)-2,2¢-bithiophene (tetracene-bithiophene),
which was then purified to device quality by gradient
sublimation. Approximately 50 mg of the purified material
was charged in a crucible and placed in a vacuum
chamber with test substrates comprised of silicon wafers
with alumina sputtered on the front and Al sputtered
on the back (Silicon Valley Microelectronics, 1500 Å
sputtered alumina, 5000 Å Al backside gate).
[attachment=22176]
Introduction
Organic electronics as a field of study has come a long
way in the past 10 years. From a literature search
covering many of the available R&D materials databases,
and using the search terms “organic thin film
transistor,” 12 publications were found for 1993, but well
over 300 were found for 2003! If the search is broadened
to include organic thin film electronic devices such as
memory, photovoltaics, and organic light-emitting diodes
(OLEDs), over 40,000 publications are found for
the period of 1998-2003. This implies a very active
research subject spanning many areas, including materials
development, device design, deposition processes,
and modeling. More researchers continue to join the
field, with few dropping out each year, even though, as
a community, we still await the key applications that
may drive organic electronics toward mature industrial
persistence.
Semiconductors
Pentacene has continued to be the most widely used
small molecule semiconductor primarily due to routinely
obtainable thin film transistor hole mobilities in excess
of 1 cm2/Vs. Researchers are beginning to investigate
long-term and operational stability in pentacene
devices,4c,12 but pentacene still remains the most reliable
benchmark material for vapor-deposited thin film transistors
(TFTs). Recent reports have increased awareness
that charge carrier mobility is not the only device
parameter to consider, and for some applications, may
not even be the most important. For RFID applications,
mobility and threshold voltage may be critically important,
but for display backplanes, threshold voltage
stability and off current may be the key parameters.13
Many reports have been made using pentacene in thin
film devices,9a,14 but several other materials have also
shown promise, deposited from either the vapor phase
or through solution delivery routes.
Tetracene-Bithiophene
We also report here our latest synthetic effort, tetracene-
bithiophene, and its device performance and
morphology as a function of substrate temperature. A
Stille coupling between 2-chlorotetracene and 5-tributylstannyl-
2,2¢-bithiophene 31 was used to prepare 5-(2-
tetracenyl)-2,2¢-bithiophene (tetracene-bithiophene),
which was then purified to device quality by gradient
sublimation. Approximately 50 mg of the purified material
was charged in a crucible and placed in a vacuum
chamber with test substrates comprised of silicon wafers
with alumina sputtered on the front and Al sputtered
on the back (Silicon Valley Microelectronics, 1500 Å
sputtered alumina, 5000 Å Al backside gate).