Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 65: Poster: Organic electronics and photovoltaics (CPP; jointly with HL, O)

HL 65.2: Poster

Mittwoch, 13. März 2013, 16:30–18:30, Poster C

Solution processing of self-assembled monolayers as charge injection layers in organic FETs. — •Milan Alt^{1, 4}, Janusz Schinke^{2, 4}, Kaja Deing^{3, 4}, Uli Lemmer¹, and Norman Mechau^{1, 4} — ¹Karlsruher Institute of Technology — ²TU Braunschweig — ³Merck KGaA, Darmstadt — ⁴InnovationLab, Heidelberg

All-solution processed organic field effect transistors (OFETs) are expected to play a key role in the mass production of organic electronic devices via high throughput printing techniques. In this study we focus on solution processing of self-assembled monolayers (SAMs) for enhancement of charge carrier injection at the metal-semiconductor interface. One necessity in order to make SAMs printable is an understanding of molecular assembly in dependency to process parameters like accumulation time and molecular concentration in the solution. We used well established benchmark materials to investigate the functionality of different benzyl-mercaptan and alkanethiol SAMs in OFETs. The methodic evaluation of OFET devices, in which the transistor effectively serves as a characterization tool, revealed an expected correlation between metal work function shift and device threshold voltage. More interestingly, an optimum ratio of accumulation time/SAM concentration has been identified. In contrast, investigations of SAM isle accumulation on crystalline Au 111 surfaces in literature reveal a saturation of work function shift when approaching a closed monolayer. This demonstrates that understanding of SAM growth mechanisms gained on single crystalline surfaces cannot naturally be transferred to assembly on printed or evaporated metal contacts.