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Details of Grant 

EPSRC Reference: EP/J002305/1
Title: Charge Carrier Dynamics and Molecular Wiring in Hybrid Optoelectronic Devices
Principal Investigator: Barnes, Dr PRF
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Swiss Federal Inst of Technology (EPFL) Tata Steel University of Oxford
Weizmann Institute of Science
Department: Physics
Organisation: Imperial College London
Scheme: Career Acceleration Fellowship
Starts: 01 October 2011 Ends: 30 September 2016 Value (£): 722,816
EPSRC Research Topic Classifications:
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Related Grants:
Panel History:
Panel DatePanel NameOutcome
14 Jun 2011 Fellowships 2011 Interview Panel C Announced
Summary on Grant Application Form
Charge Carrier Dynamics and Molecular Wiring in Hybrid Optoelectronic Devices

In the past decade there has been an explosion of interest in electronic devices using alternative materials to silicon, the traditional 'workhorse' of the semiconductor and photovoltaic industry. These alternative materials such as conducting molecules, polymers, metal oxides and metal sulphides are attractive because they can be deposited in a wide range of shapes and sizes from solution or printed onto flexible substrates. This allows low temperature, cheaper and more versatile manufacturing. They can be used to make devices such as next generation sensitised solar cells (SSCs), hybrid organic/inorganic solar cells and light emitting diodes (LEDs). These promise higher performance/cost ratios than conventional semiconductor devices. However the cost and processing advantages typically come at the expense of poor electrical charge transport due to the nature and processing of the materials used. This can lead to relatively low power conversion efficiencies in solar cells and LEDs based on these materials. Additionally variations in the energy of electrons (workfunction) at the interface between phases such as polycrystalline metal oxides and conducting polymers can cause non-ideal device behaviour leading to poor transfer of charge between the components and a corresponding loss in performance.

My proposal will address these problems by exploiting an interesting phenomenon where electrical charge is transferred between neighbouring molecules in a single continuous layer attached to a surface. This concept, known as two dimensional molecular wiring, has recently been applied in new battery technology which contains components with very poor conductivity. It allows more efficient collection of charge from the interface between the two phases in the electrochemical cell, allowing more rapid charging/discharging and more space for the active ingredients. I will work with the leaders in this field (EPFL in Switzerland) to apply molecular wiring to SSCs and hybrid optoelectronic devices. I have a strong research background related to dye sensitised solar cells (DSSCs, a particular class of SSC), and have recently been involved in a study that demonstrated molecular wiring between dye molecules covering the surface of titanium dioxide nanoparticles in liquid electrolyte DSSCs.

By applying molecular wiring in solid state SSCs and hybrid cells I hope to increase the separation and collection of charge from regions within the devices which are electrically isolated. This would lead to improved photocurrents and power conversion efficiencies. Additionally molecular wiring at oxide electrode interfaces should help to reduce variation in electron energy at interfaces by allowing neighbouring regions to reach equilibrium. This would be very attractive for the plastic electronics industry.

At Imperial College I have developed a unique series of measurements that will allow me to test the effectiveness of different configurations of molecular wiring in the solar cells. I will also work with Prof. Nelson who has expertise in molecular, charge and energy transport modelling to develop a method to screen suitable molecular wiring candidates to incorporate into the devices. I will compare these theoretical calculations with direct measurements of the conductivity through of layers of the molecules using a conducting atomic force microscope coupled with steady state and transient light sources. The results will help to direct researchers at EPFL and elsewhere towards synthesising new functional molecules for these applications. This strategy will be combined with increases in the charge separation efficiency in SSCs leading to easy to manufacture, higher performance devices.
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