Cakewalk for conducting polymers
doi:10.1038/nindia.2009.151 Published online 8 June 2009
An Indo-US research team has invented a new field-effect transistor (FET) modified with a layer of liquid crystalline semiconducting polymer1. The transistor works wonders over a wide range of temperatures and voltages. Such addition of the polymer layer to FET will have potential applications in electronic devices like flat-panel displays and photovoltaic cells.
Semiconducting polymers combine novel semiconducting electronic properties with the scope for easy shaping and manufacture of plastics. The researchers took a field-effect transistor and laid layers of silicon substrates. On top of it, they smeared a 30nm-thick layer of poly (2, 5-bis (3-tetradecylthiophen-2-yl) thieno [3, 2-b] thiophene) (PBTTT), the semiconducting polymer.
Then they applied different voltages and exposed the transistor to magnetic field. For high voltage, conductivity decreases with decreasing temperature. Measurements at low temperatures showed no change in resistance during exposure to magnetic fields up to 15 Tesla. The insensitivity to high magnetic fields confirms that transport in PBTTT is confined to one dimension.
The transport observed in PBTTT persists over a large range of charge carrier concentrations and over a large temperature range. The rigid backbone of PBTTT enables the formation of highly crystalline films with chain alignment within randomly oriented domains spanning hundreds of nanometres.
The research is very significant as semiconducting polymers like PBTTT can be used in making a wide range of electronic devices such as transistors, light-emitting diodes, solar cells and even lasers.
The authors of this work are from: Center for Polymers and Organic Solids, University of California at Santa Barbara, Santa Barbara, California, USA, Department of Physics, Indian Institute of Science, Bangalore, India, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA.
- Yuen, D. J. et al. Nonlinear transport in semiconducting polymers at high carrier densities. Nat. Mater. doi: 10.1038/nmat2470 (2009)