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Details of Grant 

EPSRC Reference: EP/J009938/1
Title: Fixing the odds: Measuring electrical randomness to improve organic electronic devices
Principal Investigator: Groves, Professor C
Other Investigators:
Researcher Co-Investigators:
Project Partners:
PETEC University of Sheffield
Department: Engineering and Computing Sciences
Organisation: Durham, University of
Scheme: First Grant - Revised 2009
Starts: 18 June 2012 Ends: 17 October 2013 Value (£): 99,788
EPSRC Research Topic Classifications:
Electronic Devices & Subsys.
EPSRC Industrial Sector Classifications:
Manufacturing Electronics
Related Grants:
Panel History:
Panel DatePanel NameOutcome
07 Dec 2011 EPSRC ICT Responsive Mode - Dec 2011 Announced
Summary on Grant Application Form
Electronic devices are ubiquitous in modern life. Transistors allow computers of all kinds to process information; a laser is at the heart of every CD and DVD player to read the information on the disk; solar panels convert the light produced by the sun directly into useful electrical energy; while light-emitting diodes are finding increasing use in lighting and displays of all kinds. Despite the diversity of the types of electronic devices and their uses, they are almost universally made from inorganic semiconductors. Inorganic materials require energy-intensive processing and careful handling during a production process that itself often results in toxic by-products. Organic materials, by contrast, offer ways of making electronic devices that are potentially much less energy-intensive and cheap. The organic materials of particular note are so-called 'conjugated polymers', that is, strings of largely carbon-containing molecules that have been specially designed to carry the electrons that constitute an electrical current. The key advantage of these polymers is that one can form an 'ink' by dissolving them in organic solvents and then manufacturing electronic devices using cheap, scalable roll-to-roll printing techniques like you would print a newspaper.

The problem with organic materials that is currently prohibiting their widespread use is the speed with which electrons can navigate their way through the material. If one had a powerful enough microscope, the electronic device made of polymers would look like a tangled mess of cooked spaghetti - with each sphagetti strand representing the backbone of a polymer chain. Electrons trying to move through this tangle can find it hard to move over the kinks of the polymer chain, and between chains. These sluggish electrons harm the performance of organic electronic devices to, instead levels below which they cannot find widespread commercial use. In order to remedy this we must understand the link between performance of the device and its structure, i.e. how the tangles of spaghetti are arranged. Defining this structure-performance relationship is especially difficult because, like in a bowl of cooked spaghetti, the arrangement of polymer chains is different everywhere. This randomness in the positions and orientations of the chains leads to randomness in the behaviours of the electrons. While this randomness in structure is well known, there are few techniques that specifically measure the electrical randomness that results, and exploit the information it contains.

In this proposal, we will pioneer the use of measurements of randomness in electrical current, or noise as it is sometimes called, produced by organic electronic devices. Noise can be understood quite well by the analogy of watching cars pass you whilst waiting at a bus stop - where electrons are the cars and the current is the number of cars that pass you in a given time. If you were to count the number of cars that pass you in successive minute intervals you will get a range of car flow rates. This fluctuation in the rate of cars passing you depends to some extent on the cars' history, i.e. what route they have taken. It is very similar for the case of electrons and current, only here the fluctuations in current inform you about the polymer chains the electrons have had to travel through en-route. For example if the current fluctuates quickly, it means the processes that are controlling the current also fluctuate quickly. Hence noise provides detailed information about what processes determine the electrical current. In the proposed research we will apply this powerful measurement to link the randomness in the behaviour of electrons with the structure of organic devices. In doing this we can make links between how the polymers and devices are made and their eventual performance, allowing chemists and device engineers to make better informed decisions, and enabling organic devices to fulfil their promise.
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