Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 73: [DS] Organic Electronics and Photovoltaics III (jointly with CPP, HL, and O)

O 73.1: Talk

Thursday, March 17, 2011, 14:00–14:15, GER 38

Influence of the thickness dependent structural order on the electrical potential distribution in the channel of OFET’s — Richa Sharma, Benedikt Gburek, •Torsten Balster, and Veit Wagner — School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen

Soluble organic semiconductors often exhibit a charge carrier dependent mobility and energetic disorder, which typically vary with layer thickness. In this study, organic field effect transistors (OFET) with different thicknesses of regio-regular P3HT as semiconductor and PMMA as gate-insulator on PET foils are investigated and analyzed statistically.

The mobility, which is very low for layers up to 10 nm, increases with the thickness over two orders of magnitude and saturates after 30 nm. This behavior is analyzed according to the Vissenberg-Matters model (VM) of the charge carrier density dependent mobility µ = µ₀ ((V_GS−V_th)/V_aa)^γ, where the disorder parameter γ decreases from 1.7 to 0.8 over the examined thicknesses proving the higher energetic disorder for thinner films. Increasing domain sizes in phase contrast AFM pictures confirm these findings.

The potential distribution within the channel, which has been measured by additional sense electrodes, is used to determine the potential steps at source and drain contact applying the VM model. The influence of the disorder parameter on the potential distribution is elucidated.