Apertureless scanning near-field optical studies of energy and charge transfer in molecular materials for opto-electronic devices.

Lead Research Organisation: University of Sheffield
Department Name: Physics and Astronomy

Abstract

The development of highly efficient electronic devices is a major goal of molecular electronics. To achieve this we need to fully understand how energy is passed from one molecule to another. Theoretically this is a simple problem to understand for two small molecules. However, in electronic devices made from blends of semi-conducting polymers energy transfer occurs at the boundaries between different polymer domains. At these boundaries many processes that occur on length scales of several nanometres can play an important role in the efficiency of the energy transfer process. To study the effect these processes have on device efficiency, I aim to develop an apertureless scanning near field microscope (A-SNOM). This microscope will allow me to study the optical properties of a variety of materials at a resolution high enough to resolve individual molecules.Using the A-SNOM I will study a variety of opto-electronic systems based on conjugated polymers. Firstly I will study blends of conjugated polymers. These polymers can be blended with other polymers or small molecules and be used as the active material in light emitting diodes or photo-voltaic devices. This will lead to a greater understanding of energy transfer in these systems and can be used to improve the efficiency of devices based on blends of conjugated polymers. The second group materials I will study will consist of light harvesting complexes (LHC) derived from specialised bacteria combined with conjugated polymers, in order that the polymers protect the bacteria while facilitating energy transfer from the polymer to the bacteria. This will represent one of the first nanoscale studies of the use of bacterial compounds in molecular electronics. Finally the A-SNOM will be used to study small numbers of interacting molecules. The high resolution of A-SNOM will allow me to image the optical properties of single molecules acting as either (energy) donor or acceptor molecules. This can be used to improve our understanding in the electronic interactions between these molecules. Studying single molecules (or two interacting molecules) will be of interest to theoreticians and will shed light on processes that occur in real devices. This is not possible using other conventional measurement techniques. Finally it will also be possible to directly correlate a molecules morphology with its energy transfer ability. The A-SNOM will allow me to make simultaneous measurements of a molecules morphology and optical properties. The results from these studies will be used in conjunction with a model photovoltaic device which will permit me to understand fundamental process which limit device performance. The device will consist of patterned strips of alternating low and high bang-gap polymers. It will be possible to incorporate results obtained during the studies outlined above to increase device efficiency.
 
Description In this work we discovered new techniques to improve the optical resolution of optical microcopy. Specifically we can trace, with very high precision, the flow of energy through single nano wires.
Exploitation Route This work is now being applied to the study of energy transfer in light harvesting protein structures.
Sectors Electronics,Energy,Manufacturing, including Industrial Biotechology

 
Description Active Filter for tip enhanced Microscopy
Amount £40,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2012 
End 01/2013
 
Description Active Filter for tip enhanced Microscopy
Amount £40,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2012 
End 06/2013
 
Description Novel STORM microscope
Amount £75,000 (GBP)
Organisation Higher Education Funding Council for England 
Sector Public
Country United Kingdom
Start 01/2012 
End 05/2012
 
Description Novel STORM microscope
Amount £75,000 (GBP)
Organisation Higher Education Funding Council for England 
Sector Public
Country United Kingdom
Start 01/2012 
End 01/2013
 
Description Storm Force Microscopy
Amount £120,000 (GBP)
Funding ID BB/I023518/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 10/2011 
End 09/2012
 
Description Andor 
Organisation Andor Technology
Country United Kingdom 
Sector Private 
PI Contribution We have worked closely with Andor over a number of years. We have helped them informally process data and given them an understanding of the application of their technologies to the Bio-Physics community. I have spent time at Andor as part of an Industrial Sabbatical.
Collaborator Contribution Andor have provided us with extra cameras when needed and also given a couple of extra cameras to us.
Impact I have spent time at Andor as part of an Industrial Sabbatical.
Start Year 2009
 
Description Collaboration with Hamamatsu photonics 
Organisation PMT Hamamatsu Photonics K.K.
Country Japan 
Sector Private 
PI Contribution Working closely with Hamamatsu we aim to help define the meaning of resolution in high resolution microscopy techniques such as STORM, PALM and SNOM. Hamamatsu invested money in to Sheffield 45K and allowed us access to its engineers and technology, which we estimate to be worth 55K.
Start Year 2012