Regensburg 2007 – wissenschaftliches Programm

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 6: Transport in Organics Materials

SYOE 6.1: Hauptvortrag

Dienstag, 27. März 2007, 14:30–15:15, H32

Theory of polymer devices: OFETs and OLEDs — •Reinder Coehoorn — Philips Research Laboratories, High Tech Campus 4, 5656 AE, Eindhoven, The Netherlands

The main challenge in the development of microscopic transport models and device models for polymer organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs) is to properly include the effects of structural and energetic disorder of the materials used. In this talk, first an overview is given of the various methods for modelling the mobility in disordered organic materials on a microscopic scale, using numerical Monte Carlo, Master Equation (ME), and analytical percolation models. From ME modelling, it is shown that disorder leads to a carrier concentration dependence of the effective steady state, and has important consequences for the frequency dependence of the complex impedance. Furthermore, it leads to a filamentary, rather then uniform current density, as quasi-3D-visualized in the talk. This is expected to affect the device efficiency and (potentially) the lifetime. Subsequently, recent experimental evidence will be presented that proofs the important role of disorder in polymer LEDs and FETs, including recent results on dual gate and ambipolar light emitting OFETs, and on blue polymer OLEDs. In the final part of the talk, an overview will be given of the various challenging questions to be solved, including the question below which (sub)layer thickness the "mobility" concept is no longer meaningful.

The results presented in this talk have been obtained in collaboration with D.M. de Leeuw (Philips Research), S.L.M. van Mensfoort, B. Ramachandhran and P.A. Bobbert (Eindhoven University of Technology) and E.C.P.Smits (University of Groningen).