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Polaron traps are ubiquitous in organic semiconductors and recent evidence suggests they might be crucial for the large observed magnetic field effects (MFEs) in organic semiconductors. Here we measure MFEs in polymer thin-film devices with engineered, radiative trap sites in order to spectroscopically investigate the influence of the traps. Surprisingly, the luminescence at the trap sites and the polymer backbone is found to have an opposite response to a magnetic field. All our results are compatible with a mechanism in which spin mixing at the traps can create the large MFEs observed on the backbone. This scenario is quantitatively confirmed by numerical drift-diffusion modeling with magnetic-field-dependent exciton densities at the traps. These insights solve an outstanding controversy within the research field., Funding Agencies|Dutch Technology Foundation (STW), Netherlands Organization for Scientific Research (NWO)

The electron-injection capability of solution-processed cesium stearate films in organic light-emitting diodes is investigated. Cesium stearate, which is expected to exhibit good solubility and film formation due to its long hydrocarbon chain, is synthesized using a straightforward procedure. Light-emitting diodes are fabricated using orange-, yellow-, and blue-emitting conjugated polymers, comprising a cesium stearate electron-injection layer deposited from ethanol solution. It is demonstrated that these devices perform as well as benchmark devices using vacuum-deposited barium as electron-injection layer, without loss of color purity. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4790592]

A dual gate transistor was fabricated using a self-assembled monolayer as the semiconductor. We show the possibility of processing a dielectric on top of the self-assembled monolayer without deteriorating the device performance. The two gates of the transistor accumulate charges in the monomolecular transport layer and artifacts caused by the semiconductor thickness are negated. We investigate the electrical transport in a dual gate self-assembled monolayer field-effect transistor and present a detailed analysis of the importance of the contact geometry in monolayer field-effect transistors., Funding Agencies|Dutch Polymer Institute [624]; Dutch Technology Foundation STW