Optoelectronics Group, Cavendish Laboratory

The research in semiconducting polymers for use as transistors is focused on the charge transport physics of organic semiconductors, and their application in field-effect transistor devices fabricated by solution- processing and direct printing techniques. This research is carried out within the Field Effect Transistor group.

Many properties of polymer semiconductor depend on the transport of charges along the polymer backbone and from one polymer chain to another polymer chain. Field-effect transistors are a convenient tool for studying these charge transport processes in conjugated polymers. Charges in polymers experience a strong electron-phonon coupling and tend to form so-called polarons. The transport of these polarons is in many respects similar to the electron transfer processes that occur in biological processes such as photosynthesis, and we have developed a number of experimental techniques to study these processes on a molecular scale.

Major areas of current research include:

• Charge transport and device physics of organic semiconductors
• Scanning probe characterization of nanoscale charge transport
• High resolution and self-aligned printing for micro- and nano-fabrication
• Study of n-type and ambipolar transport in organic semiconductors and recombination in light-emitting field-effect transistors

The devices constructed using the printing technology have resulted in high performance organic transistors on a length scale of 100 nm. These innovations are being exploited by the successful spin-off company Plastic Logic.

Observation of electron behavior in ambipolar polymer-based light-emitting transistor by optical second harmonic generation
Y. Ohshima, E. Lim, T. Manaka, M. Iwamoto and H. Sirringhaus
Journal of Applied Physics 110(1): 013715 [2011]

Efficient charge injection from a high work function metal in high mobility n-type polymer field-effect transistors
M. Caironi, C. Newman, J. R. Moore, D. Natali, H. Yan, A. Facchetti and H. Sirringhaus
Applied Physics Letters 96(18): 183303 [2010]

Device Physics of solution-processed organic FETs
H. Sirringhaus
Adv. Mat. 17 p2399 [2005]

General observation of n-type field-effect behaviour in organic semiconductors
L.L. Chua, J. Zaumseil, J.-F. Chang, E.C.W. Ou, P.K.H. Ho, H. Sirringhaus, R.H. Friend
Nature 434 p194-199 [2005]

For more information, follow the links on the left hand side, visit the FET group web pages, or the spin-off company Plastic Logic's web site.