Regensburg 2010 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 44: Organic Thin Films I

DS 44.1: Vortrag

Freitag, 26. März 2010, 10:15–10:30, H8

Charge Transport Investigation in Organic Semiconductors by Electro-Reflectance — •Steve Pittner and Veit Wagner — School of Engineering, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany

Organic semiconductors have proven to be suitable materials for electronic devices, such as organic solar cells, organic field effect transistors (OFET), and organic light emitting diodes. Generally organic semiconductors exhibit rather low charge mobility and it is crucial to understand the details of charge transport within organic material for further improvements. Disordered organic materials often exhibit a charge carrier density dependent mobility (see e.g. Vissenberg/Matters) and the aim of this work is to analyse the contribution of carriers with different mobilities during the electrical charge transport between electrodes. For this purpose the spectral fingerprint of the charge carriers under investigation is detected locally by electro-modulation spectroscopy. This is done in an OFET-like geometry with an applied alternating voltage. Clear changes of the fingerprint spectrum with the DC gate voltage as well as with the lateral distance to an electrode are detected. The changes occur at a photon energy around 1.9 eV for a poly(3-hexylthiophene) (P3HT) semiconducting layer. The depletion of the high energy shoulder clearly reflects the charge carrier population modification with gate voltage and/or distance to the injecting electrode. The changes are interpreted as time-dependent settling of the injected charge carriers to lower energy polaronic states related to the band tails of the material.