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Franco Cacialli

London Centre for Nanotechnology, London, and Department of Physics and Astronomy, University College London, UK
Organic light-emitting and photovoltaic devices: basic structure, fundamental processes and their optimisation

I will review the fundamentals of organic light-emitting and photovoltaic devices with particular emphasis on light-emitting diodes, LEDs, light-emitting electrochemical cells (LECs), and excitonic solar cells. The lecture will be structured in 4 parts covering respectively: a) Organic LEDs: after a brief introduction to their historical development and the general device architecture, I will introduce the fundamental processes taking place during electroluminescence (EL). This will be followed by a description of the physical parameters used to characterise such devices (e.g. max luminance and efficiencies) and of the strategies used for the optimisation of the device performance. This will include a section dedicated to the use of supramolecularly engineered materials, and in particular threaded molecular wires (TMWs) for the increase of the luminescence efficiency via suppression of detrimental intermolecular interactions. b) LECs: this part will cover the fundamental idea at the basis of LECs and after reviewing the most important differences with LEDs, will cover briefly the different interpretations for the behaviour of different complex devices whose commercial exploitation is still hampered by stability problems. c) Electrodes engineering: A special part of the lecture will be dedicated to the issue of electrodes engineering that is crucial to all polymer devices, not only light-emitting, but also photovoltaic diodes, PVDs, and field-effect transistors, FETs. The use of electroabsorption spectroscopy for the analysis of the energy level line-up at metal-semiconductors interfaces will be illustrated. d) Organic photovoltaic diodes, PVDs. The final part of the lecture will be dedicated to the introduction of the fundamentals of organic photovoltaic cells, and to the processes that are at the basis of their operation.