Electronic properties of polymers and organic crystals (EPPOC)

Lead Research Organisation: University of Cambridge
Department Name: Physics

Abstract

Organic semiconductors are becoming a very powerful electronic technology for applications in flexible displays and low-cost printed circuits. Their charge transport physics and ultimate performance limits are however not well understood. The objective of the proposed project is to establish an intense collaboration between the Osaka and Cambridge organic electronic groups in order to arrive at an in-depth understanding of the relationship between the device physics of conjugated polymers and molecular crystals. We will perform a broad range of directly comparable experiments on the two systems using techniques that are already available in the Osaka and Cambridge groups to understand similarities and differences in the charge transport physics of the two systems. This will include performing the first Hall effect and magnetoresistance measurements on high-mobility polymer semiconductors to compare with measurements already performed in Osaka on molecular crystals. A particularly interesting question is that of polaronic relaxation processes in molecular crystals, and we will perform the first spectroscopic measurements of charge-induced optical absorptions in molecular crystals and compare with those already performed on polymers in Cambridge. The core of the research work outlined above will be carried out by two PhD students, one registered in Cambridge, the other one registered in Osaka. Both students will interact with each other very closely, and will spend significant time during their PhD working in the other location. The two PhD students working on the project will have available the widest possible spectrum of experimental characterisation techniques, and the project will provide an excellent training environment for them to become leaders in future UK-Japan research collaborations.
 
Description The grant allowed us to develop Hall effect meausurements as a key experimental technique to characterise the charge transport physics of high mobility molecular semiconductors. The technique allows probing the degree of charge delocalisation in these materials and how it is affected by thermal motions that cause dynamic disorder in the intermolecular transfer integrals. The technique has become one of our standard tools for probing the charge transport physics of these materials and continues to be in active use.
Exploitation Route The insight gained as part of the project has already led to an appreciation in the scientific community of the importance of dynamic disorder in the transport physics of molecular semiconductors. It has led to a number of follow-on studies, in particular has motivated more recently the development of a novel electron microscopy technique, that allows quantitative determination of the amplitude of the thermal motions (Eggeman et al., Nature Materials 12, 1045 (2013)) and that has inspired a novel molecular design approach for suppressing these fluctuations (Illig, et al., Nature Communications 7, 10736 (2016)).
Sectors Electronics
 
Description This has been a highly successful project based initially on a collaboration with the group of Prof. Jun Takeya at Osaka University. The methodology developed together with Osaka based on combining Hall effect measurements with optical spectroscopy has provided new insight into the charge transport physics of high mobility molecular semiconductors, in particular the role of dynamic disorder and molecular lattice fluctuations. It has led to at least one concrete follow-on project (an industrial case studentship funded by Merck Chemicals) and has provided inspiration for multiple ongoing projects in the group, such as a project to measure directly such lattice fluctuations by electron microscopy. The project has also provided new molecular design guidelines for high mobility molecular semiconductors and is informing the molecular design and materials development activities of academic and industrial chemistry groups around the world.
 
Description Merck Ltd
Amount £63,789 (GBP)
Funding ID 8000953 
Organisation Merck 
Department Merck UK
Sector Private
Country United Kingdom
Start 10/2009 
End 03/2013
 
Description Merck Ltd
Amount £63,789 (GBP)
Funding ID 8000953 
Organisation Merck 
Sector Private
Country Germany
Start 10/2009 
End 03/2013