Pentacene-based organic field-effect transistors

Abstract

Organic field-effect transistors (FETs) have attracted considerable attention because of their potential for realizing large-area, mechanically flexible, lightweight and low-cost devices. Pentacene, which is a promising material for organic FETs, has been intensely studied. This article reviews the basic properties of pentacene films and crystals, and the characteristics of pentacene FETs fabricated under various conditions, including our recent achievement of low-voltage operating high-mobility FETs. The basic properties include the crystal polymorph, the band structure and the effective mass. These data have been used for discussion of carrier transport and mobility in pentacene films. The characteristics of pentacene FETs generally depend on the conditions of the pentacene film and the gate-dielectric surface. The dependences are summarized in the article. In addition, liquid-crystal displays and organic light-emitting device arrays using pentacene FETs are reviewed as applications of organic FETs, and complementary metal–oxide–semiconductor circuits using our low-voltage operating FETs are also shown.

Theoretical study of stability and charge-transport properties of coronene molecule and some of its halogenated derivatives: A path to ambipolar organic-based materials?

“…For instance, functionalization of the molecule with active electron-withdrawing groups is a recurrent strategy, be these groups cyano, imide, or halogen atoms, as well as heteroatom replacements of the carbon atoms within the molecular backbone. [7][8][9][10] For instance, the pentacene molecule, taken this case as an illustrative example, is considered a prototype p-type material, 11 whereas its per-fluorination allowed to obtain electron mobilities as high as 0.11 cm 2 V −1 s −1 compared to hole mobilities of 0.45 cm 2 V −1 s −1 under the same experimental conditions, showing thus comparable mobilities and ambipolar behavior. 12 Another strategy currently pursued in hydrocarbons as 2,6 :2 ,6 -terazulene revealed an asymmetrical distribution of the frontier molecular orbitals leading to (in this case) a preferred n-type behavior.…”

Electron and spin transport studies of gated lateral organic devices

“…We obtained very stable drain currents, reflecting the ordered morphology of the crystal. Figure 6 shows the current-voltage characteristics at temperatures from 7 to 300 K; the non-linear electrical characteristics indicate that injection is via field-assisted thermionic emission over an interface barrier, with an extracted activation voltage of around 1.6 V. The interface barrier at the organic-metal contact originates from the mismatch of the work function of the metal and pentacene, 37,38 along with surface adsorption 29 and the likely presence of a vacuumgap at the contact area (due to the terraced morphology of the crystal surface). The application of a gate electrode enhanced the conductivity (Figure 7), raising the signal to noise ratio; the effect was actually not very pronounced, with on/off ratio of about 5, presumably due to the geometry of the device in which the crystal is not in direct contact with the dielectric surface giving rise to the formation of surface electric dipoles.…”

Electron spin resonance observation of charge carrier concentration in organic field-effect transistors during device operation

“…This can be ascribed to the highly sophisticated design of the semiconductor materials as well as the development of fabrication techniques such as chemical treatment of the device interface by using self-assembled monolayers (SAMs). [5][6][7][8][9][10][11][12][13][14][15] On the other hand, understanding of the basic physical processes, such as charge injection or transport, as well as the electronic state of charge carriers at the semiconductor/insulator interface is still under progress. Thus the microscopic observation of charge carriers during the device operation is an essential subject in understanding the operation principle of the device, which may also contribute to design highly efficient devices.…”