Organic electronics: A faster way to move electrons
A low-cost molecule boosts the stability and amplification characteristics of solution-based polymer semiconductors
Replacing traditional rigid silicon wafers with semiconductors made from flexible polymers would herald an age of advanced, ‘wearable’ electronics. Switching to these semiconductors, known as organic field-effect transistors (OFETs), would also reduce manufacturing costs significantly. However, most plastic materials have trouble moving electrons and their polar opposites — positively charged empty ‘holes’ inside semiconductor lattices — with sufficient speed for electronic amplification.
Prashant Sonar and co-workers from the A*STAR Institute of Materials Research and Engineering in Singapore have now developed a polymer for solution-based OFET processing that has inherently high carrier mobility and extraordinary air stability1. Unlike silicon, polymers are difficult to pack into crystalline structures containing regular pathways for charge carriers. The team’s polymer, however, has specifically designed hydrogen bond interactions that create ordered networks for transporting electrons and holes.
Most polymers used in OFETs have a ‘donor–acceptor’ arrangement of conjugated molecules to enhance the mobility of charge carriers. Using special catalysts, chemists can link together small units of electron-rich and electron-poor aromatic molecules to form an alternating chain of ‘block’ co-polymers. Sonar and co-workers investigated whether fluorenone — an inexpensive and chemically stable molecule with three fused aromatic rings and a central carbonyl unit — could act as a new type of acceptor block for OFET polymers.
The researchers anticipated that the unusual polarity of fluorenone's carbonyl unit might help it stick to aromatic hydrogen atoms and improve solid-state packing. To test this concept, they made a co-polymer consisting of fluorenone and an aromatic donor known as diketopyrrolopyrrole (DPP), a compound designed to be compatible with large-scale solution processing. The resulting block co-polymer had exceptional thermal stability: it melted only at external temperatures over 300 °C.
When Sonar and co-workers used a technique called spin-coating to convert the fluorenone–DPP co-polymer into an OFET device, they observed impressive amplification characteristics and one of the highest hole mobilities ever recorded for solution-processed transistors. Their tests also showed that this material retained its valuable electronic attributes without decomposing in air — a problem that plagued earlier generations of OFETs. Optical measurements revealed the basis of this high stability: the fluorenone units make electrons in the co-polymer’s highest energy states less accessible and therefore less susceptible to air-based impurities.
“Fluorenone is a commercially available, cheap starting material, which has never been studied for OFET use before,” says Sonar. The team is now investigating how to utilize it as a novel building block for high-performance organic electronic applications by carefully ‘engineering’ chemical improvements onto its molecular framework.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering
Sonar, P., Ha, T.-J. & Dodabalapur, A. A fluorenone based low band gap solution processable copolymer for air stable and high mobility organic field effect transistors. Chemical Communications 49, 1588–1590 (2013)
A*STAR Research | Research asia research news
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....