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SUMMARY:Neither crystalline nor amorphous: Disorder\, microstructure and t
 ransport in organic semiconductors. - Alberto Salleo\, Materials Science a
 nd Engineering Stanford University\, USA.
DTSTART:20110513T090000Z
DTEND:20110513T100000Z
UID:TALK31398@talks.cam.ac.uk
CONTACT:Jenny Clark
DESCRIPTION:The promise of organic electronics is to dial in desirable pro
 perties (emission wavelength\, mobility\, chemical sensitivity) and use th
 e power of organic chemistry to rationally design new synthetic semiconduc
 tors without being limited by Nature and the periodic table.\n\nFrom the f
 undamental standpoint\, these materials are fascinating as they are neithe
 r crystalline nor amorphous and their microstructure plays a central role 
 in governing charge transport. We apply classical Materials Science concep
 ts towards understanding how organic semiconductors “work”. Using adva
 nced synchrotron-based X-ray characterization techniques we are able to de
 fine and measure structural order at different length-scales. I will show 
 that understanding disorder is the key to determining charge transport mec
 hanism. For instance\, static cumulative disorder (e.g. paracrystallinity)
  –which we devised how to measure quantitatively–provides a fundamenta
 l justification to using a mobility edge model with an exponential distrib
 ution of tail states in the gap. Furthermore\, we are able to provide a st
 ructural interpretation of these trap states\, which for instance manifest
  themselves as a broad sub-threshold region in transistors. Paracrystallin
 e disorder allows to rank organic semiconductors thereby allowing to\ndete
 rmine whether shallow traps or grain-boundaries limit transport this regar
 d\, I will show that engineering the microstructure of organic semiconduct
 ors leads to new insights in the role of grainboundaries in charge transpo
 rt. Understanding the relationship between microstructure and transport is
  of fundamental importance for the rational design of new synthetic semico
 nductors.
LOCATION:Kapitza Building Seminar Room\, Cavendish Laboratory\, Department
  of Physics
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