The morphology of the thin active layer is one of the main parameters that influence charge transport properties and thus the functioning of organic field-effect transistors (OFETs). To understand this relationship, it is desirable to have techniques able to locally probe the electronic properties along the channel of a working device. In this contribution we show that with Charge Modulation Microscopy (CMM) it is possible to optically map the charge density in a high-mobility n-type OFET with a lateral resolution of about 500 nm; this is achieved by measuring the local polaronic absorption and bleaching features in a laser scanning confocal microscope. Interestingly, the signal is sensible only to the few-nanometers thick accumulation layer, allowing the investigation of the properties of the electronic states at the semiconductor-dielectric interface involved in charge transport processes. By using a polarized light probe, we highlight the presence of a micrometric texture in the map of the charge induced features, which can be related to regions of preferential alignment of the polymeric backbones. These regions of preferential alignment could play a crucial role in the transport properties of polymeric semiconductors, especially in novel n-type high-mobility materials in which the influence of morphology at different scales is currently highly debated.

Correlation between local morphology and electronic states in organic field-effect transistors investigated by charge modulation microscopy

MARTINO, NICOLA;
2013

Abstract

The morphology of the thin active layer is one of the main parameters that influence charge transport properties and thus the functioning of organic field-effect transistors (OFETs). To understand this relationship, it is desirable to have techniques able to locally probe the electronic properties along the channel of a working device. In this contribution we show that with Charge Modulation Microscopy (CMM) it is possible to optically map the charge density in a high-mobility n-type OFET with a lateral resolution of about 500 nm; this is achieved by measuring the local polaronic absorption and bleaching features in a laser scanning confocal microscope. Interestingly, the signal is sensible only to the few-nanometers thick accumulation layer, allowing the investigation of the properties of the electronic states at the semiconductor-dielectric interface involved in charge transport processes. By using a polarized light probe, we highlight the presence of a micrometric texture in the map of the charge induced features, which can be related to regions of preferential alignment of the polymeric backbones. These regions of preferential alignment could play a crucial role in the transport properties of polymeric semiconductors, especially in novel n-type high-mobility materials in which the influence of morphology at different scales is currently highly debated.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/762879
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