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The role of the electrode configuration on the electrical properties of small-molecule semiconductor thin-films

Gomes, H.L.

Organic Electronics Vol. 49, Nº NA, pp. 107 - 113, October, 2017.

ISSN (print): 1566-1199
ISSN (online):

Scimago Journal Ranking: 1,09 (in 2017)

Digital Object Identifier: 10.1016/j.orgel.2017.06.041

Abstract
This paper presents a systematic analysis of the electrode configuration influence on the electrical properties of organic semiconductor (OSC) thin-film devices. We have fabricated and electrically characterized a set of planar two-terminal devices. The differences in I-V characteristics between the top and bottom contact structures are presented and analyzed. Top-contact configurations have a linear current vs. electric field behavior, while the bottom-electrode devices display a transition from ohmic to space-charge-limited conduction regime. The transition is temperature- and thickness-dependent. Finite-element calculations show that when the OSC film is connected using top electrodes, the current flows through the OSC bulk region. On the other hand, the bottom-electrode configuration allows most of the current to flow near the OSC/substrate interface. The current probes interfacial states resulting in a space-charge conduction regime. The results shed some light on the so-called “contact effects” commonly observed in organic thin-film transistors. The findings presented here have implications for both the understanding of the charge transport in OSC films and the design of organic semiconductor devices.