Contacts in Organic Field-Effect Transistors

Organic semiconductors are versatile materials for emerging low-cost, lightweight, flexible devices, but their incorporation in consumer applications is delayed by inadequate performance. Inefficient charge injection at the electrode/semiconductor interface represents a significant hurdle in the pursuit of the promised potential of organic semiconductors. Moreover, with increasing the effective mobility of organic semiconductor layer and reducing the channel dimensions, this problem becomes even more prevalent. In this talk, I will focus on describing the origin and characterization of contact effects in organic field-effect transistors and their impact on device performance and accuracy in extraction of charge carrier mobility. Several types of manifestations of contact effects will be presented, as well as their impact on the device characterization. I will discuss methods for reducing contact resistance and will emphasize on a simple strategy consisting of developing high workfunction surface domains at the surface of the injecting electrodes to promote channels of enhanced injection [1]. This led to contact resistances of 200 Ωcm and device charge carrier mobilities of 20 cm²/Vs independent of the applied gate voltage. The proposed approach is efficient for both small molecule and polymeric thin-film transistor devices, and can be generally applied in all common processes and device architectures. In addition to allowing the demonstration of high-mobility transistors with near ideal current-voltage characteristics, the use of this method leads to accurate measurement of the charge carrier mobility, a critical step in a rational material design.

[1] Zachary A. Lamport, Katrina J. Barth, Hyunsu Lee, Eliot Gann, Sebastian Engmann, Hu Chen, Martin Guthold, Iain McCulloch, John E. Anthony, Lee J. Richter, Dean M. DeLongchamp and Oana D. Jurchescu, Nat. Commun (2018) DOI: 10.1038/s41467-018-07388-3