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Abstract The fabrication of diodes by inkjet printing has been hampered by difficulties in printing low work function metals required to establish Schottky barriers with organic semiconductors. This limitation has been a major roadblock in the use of inkjet printing technology for the development of organic rectifying diodes. This paper presents the fabrication and characterization of a novel inkjet-printed metal- organic insulator- organic semiconductor diode on flexible plastic substrates. The structure consists of a polymeric insulator/semiconductor interface sandwiched between two silver electrodes. It is proposed that the rectification properties are due to a voltage controlled leakage current across the insulator/semiconductor interface. The current across the insulator is caused by the formation of a semiconductor brush-like morphology into the underneath porous insulator layer. The carrier injection into the insulator follows a thermionic emission model. Temperature dependent measurements reveal an interfacial barrier height between 0.97 eV and 0.36 eV depending on the morphology and type of insulator layer used. Metal- organic insulator- organic semiconductor based diodes show rectification ratios up to 150 at |10V| and a current density up to approximately 1 μAcm−2. The simple fabrication process of the diodes also makes it advantageous for scaling up to roll-to-roll production. Graphical abstract Image 1 Highlights • The organic Metal-Insulator-Semiconductor (MIS) based diodes show a rectification ratios of 150 at |10V| and a current density of 1 μAcm−2. • It is shown that inkjet printing can be used to fabricate rectifying diodes using a MIS structure and ohmic metal contacts. • The semiconductor-polymer intermixing creates a polymer brush-like morphology that thinner the insulating polymer layer. • The physical model proposed for MIS diodes is only dependent on the insulator morphology and independent of the type of polymer used. [ABSTRACT FROM AUTHOR]

A flexible, biological field-effect transistor (BioFET) for use in biosensing is reported. The BioFET is based on an organic thin-film transistor (OTFT) fabricated mainly by inkjet printing and subsequently functionalized with antibodies for protein recognition. The BioFET is assessed for label-free detection of a model protein, human immunoglobulin G (HIgG). It is characterized electrically to evaluate the contribution of each step in the functionalization of the OTFT and to detect the presence of the target protein. The fabrication, structure, materials optimization, electrical characteristics, and functionality of the starting OTFT and final BioFET are also discussed. Different materials are evaluated for the top insulator layer, with the aim of protecting the lower layers from the electrolyte and preserving the BioFET electrical performance. [ABSTRACT FROM AUTHOR]