Organic Thin Film Transistors for Large Area Electronics

Organic semiconductors have been studied since the late 1940’s.1 However, until recently
they had failed to have a significant practical impact in optoelectronic applications, despite of the
fact that a very large number of experimental and theoretical studies have been published. Initial
industrial applications of organic semiconductors exploited their photoconductive properties in
xerography. The initial demonstration of organic electroluminescent diodes2,3 and organic thinfilm
field-effect transistors (OTFTs)4,5,6 based on either small organic molecules2,5 or conjugated
polymers3,4,6 and the impressive improvements in performance and efficiency of organic devices
during the last decade7,8,9,10 attracted the interest of industry and opened the way to practical
applications for organic semiconductors. In this review we will focus on the progress in the field
of organic thin-film field-effect transistors in recent years. We will restrict our review to
transistors in which the organic active layer is an approximately two-dimensional structure, such
as a thin film. It has been shown that only a few organic monolayers are sufficient for proper
transistor operation.11,12 We will make an effort to describe the broad spectrum of materials,
fabrication processes, designs, and applications of OTFTs, with an emphasis on papers published
during the last few years. Older papers that, in the authors’ opinion, played a pivotal role in
shaping the OTFT field are also reviewed, but the reader is encouraged to look up a number of
previously published review papers that cover that earlier period in more detail.[13,14,15, 16, 17,18,19].
Reported results from single crystal organic field effect transistors will be used to define the
upper limit of performance of OTFTs and to gain a better understanding of the underlying device
physics. Results from devices in which the active channel consists of a single organic molecule
or a more extended structure such as a carbon nanotube, will not be discussed, despite the strong
interest that recently has developed for such transistors. 20, 21, 22, 23, 24