Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 110: Molecular Films: Morphology, Electronics, Photovoltaics
O 110.8: Vortrag
Freitag, 24. März 2017, 12:30–12:45, GER 38
Diffusion Properties of Molecular Dopants in Organic Semiconducting Polymers — Patrick Reiser1,3, Vipilan Sivanesan2,3, •Sebastian Beck2,3, Wolfram Jaegermann1,3, and Eric Mankel1,3 — 1Institute for Materials Science, Technische Universität Darmstadt — 2Kirchhoff-Institut für Physik, Universität Heidelberg — 3InnovationLab GmbH, Heidelberg
In this study we investigate the diffusion of a solution-processable metal-organic molybdenum complex (Mo(tfd-CO2Me)3) acting as p-dopant in Poly(3-hexylthiophen) (P3HT) thin films. In general, doping of organic semiconductors significantly increases the charge carrier concentration and improves transport and injection at contacts. However, in photo-active layers and at donor-acceptor interfaces a molecular dopant can act as exciton quencher. Therefore the diffusivity of molecular dopants is of interest for device stability and lifetime. Here, the dopant diffusion is measured at room temperature in 50nm polymer films using long-term Photoemission Electron Spectroscopy (PES) measurements. Molar surface fractions are derived from characteristic core-level emission lines. A simple analytical model can be employed to determine diffusion coefficients from time-dependent changes in surface doping ratios. We observe an exponential concentration dependency of the diffusion constant, which gives insight into the specific diffusion mechanism.