Research Project Highlight

Minimal Cores for High Mobility N-Channel Transistor Semiconductors

minimal coresThere has been extensive effort toward developing new organic semiconductors for thin film transistors due to their applications in complementary circuits, flat-panel displays and sensors.

Since the report of naphthalenetetracarboxylic diimides as air stable n-channel materials with mobility up to 0.1 cm2/Vs, a large number of n-channel materials have been based on various rylene tetracarboxylic diimides (such as naphthalene, anthracene or perylene tetracarboxylic diimides). Best known as segments of highly insulating polyimide dielectrics, pyromellitic diimides have the simplest aromatic ring (benzene) in the center, and the tetracarboxylic diimides on both sides of the benzene ring.

In Prof. Katz’s group this simple structure was found to be a sufficiently conjugated core for the construction of n-channel organic semiconductors. Pyromellitic diimides with different fluorinated side chains can be easily synthesized by a one-step reaction. As an example, the electron mobility for the vacuum sublimed material [N, N’-bis(4-(trifluoromethyl)benzyl)] in a transistor was found to be as high as 0.074 cm2/Vs in vacuum. Pyromellitic diimides are more readily available than the higher rylenes already investigated, are highly transparent and chemically stable, and lead to processable and electronically tunable derivatives. These pyromellitic diimides offer great opportunity for both scientific exploration and utilization in organic and polymer-based devices.

Organic semiconductors for use in plastic electronic devices and other alternative active circuits such as display backplanes are generally hole-transporters. It is much more challenging to design electron transporters, which are often needed to complete a circuit or even a single device.

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