Abstract
The interface between the semiconductor and the dielectric layer plays a crucial role in organic field-effect transistors (OFETs) because it is at the interface that charge carriers are accumulated and transported. In this study, four zwitterionic benzoquinonemonoimine dyes featuring alkyl and aryl N-substituents were used to cover the dielectric layers in OFET structures. The best interlayer material, containing aliphatic side groups, increased charge carrier mobility in the measured systems. This improvement can be explained by the reduction in the number of the charge carrier trapping sites at the dielectric active layer interface from 1014 eV−1 cm−2 to 2 × 1013 eV−1 cm−2. The density of the traps was one order of magnitude lower compared to the unmodified transistors. This resulted in an increase in charge carrier mobility in the tested poly [2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPPDTT)-based transistors to 5.4 × 10−1 cm2 V−1 s−1.
Highlights
The interface between semiconductors and dielectrics has attracted much attention due to its effects on the morphology of organic semiconductors (OSCs) and charge transport in organic field-effect transistors (OFETs) [1]
The presence of alkyl chains borne by OSC molecules implies arrangements in which the long axes of the OSC molecules are parallel to the substrate surface
The quality of the semiconductor–gate dielectric interface is critical for the performance of OFETs [8,9,10]
Summary
The interface between semiconductors and dielectrics has attracted much attention due to its effects on the morphology of organic semiconductors (OSCs) and charge transport in organic field-effect transistors (OFETs) [1]. Important parameters for the semiconductor–insulator interface include insulator surface roughness, surface energy, surface polarity, and the dielectric constant [3] These parameters can combine to produce several effects, such as changes to the morphological structure of the semiconductor thin film and improved charge transport performance, with strong dependence on the hydrophobicity of the substrate surface. The most favorable stacking of OSC involves face-to-face π-π interactions [4], which generate the shortest intermolecular distances and very good π-electron delocalization This enables improved charge carrier transport between molecules by hopping [5]. The protocol for such modification requires the use of high temperatures, oxygen plasma treatment, or piranha acid (i.e., an aqueous H2SO4/H2O2 solution) In this context, the quality of the semiconductor–gate dielectric interface is critical for the performance of OFETs [8,9,10]. A series of zwitterionic BQMIs (1–4) used as modifiers of the dielectric surface, and the schematic structure of the DPPDTT organic semiconductor
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