A Low-cost, Versatile Method for Fabricating Thin Films to Generate High-performance Organic Thin Film Transistors

This novel method results in the production of high performance organic thin film transistors (OTFTs) having a field effect mobility (µ) approximately equivalent to those produced from organic single crystals at a fraction of the cost. This method is inexpensive to implement, allows for very efficient power consumptions (0.7V threshold voltage), delivers high-throughput at low cost and better uniform reproducibility than other organic thin film coating techniques. This technology can be easily transferred to the fabrication of other electronic devices requiring high carrier mobility from organic materials.

Invention Summary

Researchers at Wake Forest University have developed a novel method for controlling the crystallization of the organic semiconductor channel material in organic thin film transistors. The measured device performance approaches the fundamental limits of the material, as determined from single crystal measurements. The significant OTFT performance boost obtained by this method is due to the substantial reduction in trap density (Nit) at the organic/dielectric interface as a result of improved crystalline order. The Nit estimated for these OTFTs is about a factor of two lower than that determined for all other OTFTs obtained by solution deposition methods. This novel method allows the materials to establish potential energy minima, characterized by reduced fluctuations in molecular spacing and overlap.

Competitive Benefits

  • Field-effect mobility (µ) of poly-crystalline organic thin film transistors (obtained using the Wake Forest method) is similar to single crystal OFETs
  • Method produces OTFTs that operate at low voltages and hence efficient power consumption
  • The OTFTs fabricated by the Wake Forest method outperform all OTFTs obtained by other solution deposition methods
  • Substantial capital equipment not necessary to implement this method
  • Relatively inexpensive method to adopt
  • Method is easily transferred to the fabrication of other organic devices, such as organic photovoltaics and sensors

Application Fields

Flexible displays, electronic paper, sensors, disposable and wearable electronics, and medical devices

Stage of Development

  • Demonstrated the efficiency of the method using four separate small molecule organic semiconductors
  • Validated the performance and operation at low voltage for efficient power consumption
  • Design has been recognized in Nature and Nature Materials (see other side)

Background

  • Thin film transistors (TFTs) made of inorganic semiconductor materials, such as silicon or compound semiconductors, have dominated the mainstream electronics industry.
  • Unfortunately, processing methods for fabricating these inorganic semiconductor devices are becoming increasingly complex, resulting in higher production costs.
  • While single crystal organic field-effect transistors (OFETs) are used as model systems, industry has embraced solution-deposited organic thin film transistors (OTFTs) because they offer significant processing advantages, flexibility of organic materials, application diversity and lower cost.
  • However, although solution-deposited OTFTs are significantly less tedious to manufacture than single crystal OFETs, the solution-deposition process has not been readily adopted by industry due to insufficient device performance and poor reproducibility.
  • The development of this novel Wake method now allows for the manufacture of solution-deposited OTFTs that are significantly easier to manufacture and can be scaled up for use in large area electronics, yet have performance characteristics matching, or exceeding, single crystal OFETs.

Inventors

Oana Jurchescu, PhD
Department of Physics

Peter Diemer
Department of Physics

Patents

PCT/US2013/061463

Licensing Contact

Charlie Shaw, PhD
chshaw@wakehealth.edu
+1.336.716.3729

Reference #: WFU 12-52

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