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WFU Physics Colloquium

TITLE: Enhancing the Electrical Performance of Organic Field-Effect Transistors Through Interface Engineering

SPEAKER: Jeremy W. Ward

Ph. D. Presentation
Mentor: Professor Oana Jurchescu

TIME: Thursday, April 30, 2015 at 2:00 PM

PLACE: Room 101 Olin Physical Laboratory

All interested persons are cordially invited to attend.


Recent decades have been witness to a fast transition into an era consumed with technology. A common thread among all electronic applications is the field-effect transistor (FET); a small electrical switch that can control the current flow. The most common material used in FETs today is silicon. Materials used in silicon-based electronics have now begun to be complemented by, and in some case replaced by, organic-based (i.e. carbon- based) materials. Due to weaker interactions between the molecules of organic materials, these compounds can be dissolved into a liquid to form an ink. This ink can then be deposited into a film by using low-cost, low- thermal budget methods such as roll-to-roll printing and spray-processing, thus significantly increasing the manufacturing versatility over the brittle silicon-based materials. Organic field-effect transistors (OFETs) fabricated from solution-based methods create pathways to fabricating electronic applications that are: flexible, transparent, large-area, low-power consuming, and/or even wearable.

In this presentation, I will discuss progress in addressing three challenges still associated with the incorporation of OFET devices into mainstream electronics:

  1. The environmental stability of organic semiconductors (OSC),
  2. The low device performance and high operating voltages;
  3. Insufficient understanding about the relation between organic semiconductor processing, microstructure, and its electrical properties.

In this work, we discovered a temperature-dependent phase transition in the commonly used organic semiconductor, diF-TES ADT, established additional design rules for the relationship between OSC and self- assembled monolayer (SAM) treated surfaces within an OFET structure, and explored how different processing parameters impact the OSC film morphology and resulting electrical properties. We employed the structural characterization techniques of grazing-incidence x-ray diffraction (GIXD) and microbeam grazing-incidence wide x-ray scattering (μGIWAXS) and compositional characterization techniques of polarization modulation- infrared reflection-adsorption spectroscopy (PM-IRRAS). The electrical properties of the films and devices were studied using Kelvin Probe measurements and both ambient and temperature-dependent FET measurements.

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100 Olin Physical Laboratory
Wake Forest University
Winston-Salem, NC 27109-7507
Phone: (336) 758-5337, FAX: (336) 758-6142