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SYOH: Organic and Hybrid Systems for Future Electronics

SYOH 3: Electronic Structure and Transport Properties

SYOH 3.3: Vortrag

Donnerstag, 11. März 2004, 16:30–16:45, H37

Influence of Defect States on the Electronic Transport of Pentacene Thin Film Transistors — •Pravesh Kumar¹, Dietmar Knipp^1,2, Armin R. Volkel², and Veit Wagner¹ — ¹International University Bremen, School of Science and Engineering, Germany — ²Palo Alto Research Center, Palo Alto, USA

The influence of acceptor and donor like defect states on the current voltage characteristics of polycrystalline pentacene thin film transistors (TFTs) were explored. The thermally evaporated pentacene films were prepared on organic and inorganic dielectrics. Careful control of the preparation conditions leads to TFTs with very similar mobility of 0.4 cm²/Vs and on/off ratio > 10⁸ on thermal oxide, silicon nitride and poly-vinyl phenol (PVP) dielectrics. To gain insides in the electronic transport behavior of the organic TFTs we used a one-dimensional transistors model. The model assumes an exponential distribution of defect states in the bandgap [1]. The experimental data can be described by a steep exponential distribution of donors close to the valence band and a shallower distribution of acceptors deeper in the bandgap. The influence of different preparation conditions of the pentacene film and the organic dielectric PVP will be discussed in greater detail by a comparison of experimental and simulation data. Dihexylquaterthiophene (DH4T) was also used to fabricate the thin film transistors. The mobility and the on/ off ratios for pentacene and DH4T thin film transistors were compared. [1] A.R. Volkel, R.A. Street, D. Knipp, Phys. Rev. B66, 195336 (2002).