Dr J Clark

Dorothy Hodgkin Research Fellow

Optoelectronics Group

Cavendish Laboratory

University of Cambridge

Research Interests:

Conjugated polymer-based solar cells are potentially an important and economically competitive alternative to energy generation from fossil fuels, as large areas are cheap to produce using standard printing technologies. A problem to overcome, however, is their low efficiency. It has been suggested that increased inter-chain interactions are key to increasing efficiencies, but no full understanding has yet emerged. We therefore use model systems and femtosecond pump-probe spectroscopy to perform systematic studies of the effect of inter-chain interactions on charge photogeneration mechanisms in conjugated polymers. This work is done in collaboration with Prof. Frank Spano, Temple University, Philadelphia.

Conjugated polymer-based photonic devices:

The high optical gain co-efficient of conjugated polymers - even in the solid state - make them attractive for a variety of photonic applications, such as compact, tuneable and cheap solid-state lasers and amplifiers. We study the optical loss and gain processes involved in such devices. In addition, we aim to exploit charge photogeneration in conjugated polymers to produce efficient ultrafast all-optical switching devices, with high on/off ratios and ultrafast (sub-100fs) response times. (Collaboration with Prof. Guglielmo Lanzani, Politecnico of Milan, Italy).

Biography

• 2007-2009: Postodoctoral Research Associate, Politecnico di Milano, Italy.
• 2007: PhD in Physics, University of Cambridge, UK.
• 2003: MSci in Physics, Imperial College, London, UK.

Selected Publications

• J. Clark, J-F. Chang, F. C. Spano, R. H. Friend and C. Silva. "Determining exciton bandwidth and film microstructure in polythiophene films using linear absorption spectroscopy." Appl. Phys. Lett. 94, 163306 (2009).
• J. Clark, L. Bazzana, D. D. C. Bradley, J. Cabanillas-Gonzalez, G. Lanzani, D. G. Lidzey, J. Morgado, A. Nocivelli, W. C. Tsoi, T. Virgili, and R. Xia. "Blue polymer optical fiber amplifiers based on conjugated fluorene oligomers" J. Nanophotonics 2, 023504 (2008).
• J. Clark, C. Silva, R. H. Friend and F. C. Spano. "Role of Intermolecular Coupling in the Photophysics of Disordered Organic Semiconductors: Aggregate Emission in Regioregular Polythiophene" Phys. Rev. Lett. 98, 206406 (2007).

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