Electrical properties
- Bound charges in semiconducting organic materials can be thought of in different ways. Real materials are usually highly disordered.
- An exciton within a diffusion length of a percolation path can contribute to photocurrent in dye blends
The semiconductor properties of certain "conjugated" polymers have been the subject of intense research around the world. Charge transport is rather different to that encountered in more traditional semiconductors. Understanding the mechanisms of charge and exciton diffusion, and of charge separation, plays a key role in making efficient devices. Interfaces in polymer "blends", multilayer structures, and mixtures of polymers with inorganic nanomaterials are all actively studied.
We have considerable choice in fabrication techniques, and the performance of devices is dependent on a wide range of parameters.
Experimental techniques of particular interest are: applying high pressures, where the decrease in lattice constant is more likely to make electron orbitals overlap on neighbouring molecules; the use of pulsed techniques to investigate changes in population of excited species or trapped charge; and the study of surface potential in active FET devices using a high resolution Kelvin Probe.
X-ray Microscopy of Photovoltaic Polyfluorene Blends: Relating Nanomorphology to Device Performance
C.R. McNeill, B. Watts, L. Thomsen, H. Ade, N.C. Greenham, P.C. Dastoor
Macromolecules 40 (9) p3263-3270 [2007]
Morphological Dependence of Charge Generation and Transport in Blended Polyfluorene Photovoltaic Devices
H.J. Snaith, R.H. Friend
Thin solid Films 451-452 p567-571 [2004]
Semiconductor device model applied to electrically pulsed polymer LEDs
N. Tessler, D.J. Pinner, R.H. Friend
Synth. Met. 111 p269-272 [2000]
Correlation between Surface Photovoltage and Blend Morphology in Polyfluorene-Based Photodiodes
M. Chiesa, L. Bürgi, J.-S. Kim, R. Shikler, R.H. Friend, H. Sirringhaus
Nano Lett. 5 (4) p559-563 [2005]
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