Regensburg 2010 – scientific programme

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DS: Fachverband Dünne Schichten

DS 3: Organic Electronics and Photovoltaics I (Joint Session DS/CPP/HL/O)

DS 3.4: Talk

Monday, March 22, 2010, 11:00–11:15, H8

Spatially resolved, polarization dependent absorption and photocurrent measurements of pentacene based OFETs — •Christian Westermeier, Matthias Fiebig, and Bert Nickel — Department für Physik and CeNS, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München

Pentacene is a promising candidate for organic electronics and optoelectronic applications due to its high charge carrier mobility and strong absorption properties. Forming a triclinic herringbone structure, its optical properties are highly anisotropic [1]. Pentacene films show a thin-film-phase texture. The grains inducing the texture should absorb linear polarised light depending on their orientation with respect to the direction of polarisation.

Here we use local illumination of the transistor channel in a confocal laser scanning setup with a spatial resolution in the submicron regime [2]. The pentacene grains in the channel of our OFETs exhibit a size of a few microns in diameter. The absorption of separate grains is found to be strongly dependent on the polarisation of the incident light, as expected. Thus, the scanning technique allows for imaging of grain orientation with a submicron resolution over large areas.

Absorption being the initialising step to generate excitons is important for optoelectronic devices like solar cells and the photoresponse of transistors. The influence of polarisation on the spatially resolved photocurrent of pentacene OFETs will be discussed.

[1] M. Dressel, et al., Opt. Express 16, 19770-19778 (2008)

[2] M. Fiebig, et al., Appl. Phys. A 95, 1, 113-117 (2009)