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the mobility of the material. In addition, highly order structures and arrangements may

facilitate the intermolecular hopping process, by bringing closer the coupling of

π bonding system and increase carrier mobility. The upper limits of carrier mobility in

organic semiconductor fall between 1-10 cm2 V–1 s–1. 1 This is because intermolecular

interaction in organic semiconductor is via van der Waal force which is quite weak. Van

der Waal interaction account for bonding energy smaller than 10 kcal mol–1 and sets the

upper limit for mobility because the vibrational energy of the molecules reaches a

magnitude close to that of the intermolecular bond energies at or above room

temperature.3 One of the most exciting things about organic semiconductors is that their

electric performance has increased dramatically in the past decade and that makes them

competitive in electronic devices that do not need high speed switching. Although their

mobility is still three order of magnitude smaller compare to inorganic semiconductor,

they have the ability to enable applications that are not achievable using current silicon

technology by taking advantage of their unique processing characteristics. Some of the

characteristics include low temperature deposition on large substrate area, low cost

manufacturing using printing and spin-coating. Organic semiconductors enable displays

to be fabricated on a plastic substrate which currently is not possible because of the high

processing temperature of amorphous silicon. Organic semiconductors will allow devices

such as OTFTs to be processed at room temperature, thus making it compatible with

flexible electronics.

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