How to Stabilize Organic Semiconductors in Atmospheric Conditions (2010.8.23)
Electronic displays that can be rolled up like newspapers, televisions that can be hung on walls like calendars, or computers that can be put on like clothes are fascinating ideas still to be realized. But technology certainly has evolved in this direction. A research team led by Professor Chan Eon Park of POSTECH’s Chemical Engineering Department has come forth with a breakthrough with organic electronics.
The team’s work focuses on a specific type of Organic Thin- Film Transistor (OTFT) called n-type organic semiconductors. The ‘n’ stands for negative, indicating the fact that negative electrons, instead of ‘holes,’ are the carriers of electricity. Generally, they are combined with positive-type semiconductors to become an inverter or semiconductor diode.
But n-type OTFTs had the drawback of being low in their performance, especially when compared to silicon semiconductors. Also, because of their low durability, it was very difficult to produce a sustainable complementary inverter, which is a necessary element for organic electronic devices. This is particularly why Professor Park’s recent development is gaining attention.
His work with Jaeyoung Jang, a Ph.D. candidate in his lab, enabled the current technology to increase the ‘gain’ of complementary inverters as high as 50, in atmospheric conditions. A gain can be understood as a numerical value that represents the performance of an inverter, which measures the ability of a circuit to increase the power or amplitude of a signal from the input to the output.
Furthermore, the team succeeded in stabilizing the performance of n-type semiconductors for more than 120 days. Their success has been marked extraordinary by the worldrenowned journal of material sciences, Advanced Functional Materials, and was introduced as the cover paper on the August 23rd version.
The n-type OTFT they developed is made of ring-shaped olefin macromolecules, which has a high thermal stability with a glass transition temperature of 181°C. Olefins, also known as alkenes, are unsaturated hydrocarbon chemical compounds that have at least one carbon-to-carbon double bond. Professor Park revealed that his team modified the olefin macromolecule to be more heat-resistant without undergoing any change in its essential property. They also used an n-type organic semiconductor with a self-assembling property at a temperature lower than glass transition temperature.
As the newly discovered OTFT can perform well for more than 120 days without any special shield, commercialization may be probable with a relatively short period for production. Consequently, experts are expecting a cut in production costs. Professor Park commented that “we hope to expedite the commercialization of organic electronic circuits by ameliorating the capacity and longevity of this n-type OTFT, which may allow us an advantage in acquiring the core technology in the field.”