Regensburg 2007 – scientific programme

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

SYOE 5: Organic Devices

SYOE 5.2: Talk

Tuesday, March 27, 2007, 12:00–12:15, H1

Ambipolar transport and light emission in polymer field-effect transistors in top gate geometry — •Jana Zaumseil, Carrie Donley, Ji-Seon Kim, Chistopher McNeill, Richard Friend, and Henning Sirringhaus — Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom

We have recently demonstrated that ambipolar charge transport is a generic feature of a wide range of polymer field-effect transistors (FETs) when appropriate injecting electrodes and trap-free dielectrics are used. An intriguing feature of ambipolar FETs with simultaneous hole and electron accumulation is the radiative recombination of opposite charge carriers within the channel, and thus light emission. Here we demonstrate ambipolar light-emitting FETs based on electroluminescent conjugated polymers in bottom contact/top gate geometry using gold electrodes and polymer gate dielectrics. We observe light emission from a narrow recombination zone whose position is controlled by the applied gate and source-drain voltages and depends on the ratio of hole to electron mobility and contact resistance. The light output is proportional to the drain current with quantum efficiencies comparable to those of polymer LEDs despite very high current densities. Width and intensity distribution of the emission zone were found to depend strongly on the microstructure of the polymer film. Light-emitting FETs thus allow insight into the transport properties of organic field-effect transistors that are not obvious from current-voltage characteristics alone.