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SUMMARY:Disorder-Order transitions in π-conjugated polymers and their imp
 act on device performance
DTSTART:20171204T131500
DTEND:20171204T141500
DTSTAMP:20260510T043124Z
UID:a8441fc9328faaeefb9f2ca3e1c496a33805bc6a49911b25c2ff4d62
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Anna Köhler\, University of Bayreuth\, Germany\nThe agg
 regation of p-conjugated materials significantly impacts on the photophysi
 cs\, and thus on the performance of optoelectronic devices. Nevertheless\,
  we know comparatively little about the laws governing aggregate formation
  of p-conjugated materials from solution. In this talk\, I shall compare\,
  discuss and summarize how aggregates form for three different types of co
 mpounds\, that is\, homopolymers\, donor-acceptor type polymers and low mo
 lecular weight compounds. To understand how aggregates form\, we employ te
 mperature dependent optical spectroscopy\, which is a simple yet powerful 
 tool for such investigations. I shall discuss how optical spectra can be a
 nalysed to identify distinct conformational states and to obtain quantitat
 ive information on changes in the inter-chain coupling\, the conjugation l
 ength and the oscillator strength upon aggregate formation. We find aggreg
 ate formation to proceed alike in all these compounds by a coil-to-globule
  like first order phase transition. Notably\, the chain expands before it 
 collapses into a highly ordered dense state. I will address the role of si
 de chains and the impact of changes in environmental polarization\, as wel
 l as the implications of short-range order for the performance of organic 
 electronic devices\, notably solar cells.\n \nRefs:\nF. Panzer\, H. Bäss
 ler\, A. Köhler\n„Temperature-induced order-disorder transitions in sol
 utions of conjugated polymers probed by optical spectroscopy“\nJ. Phys. 
 Chem. Lett. 2017\, 8\, 114\nM. Reichenberger et al.\n„The effect of inte
 rmolecular interaction on excited states in p-DTS(FBTTH2)2\nJ. Chem. Phys.
  2016\, 114\, 074904\nHeinz Bässler and Anna Köhler\n„Hot or cold: How
  do charge transfer states at the donor-acceptor interface of an organic s
 olar cell dissociate?”\nPhys. Chem. Chem. Phys. 2015\, 17\, 28451\nF. Pa
 nzer et al.\n“The impact of polydispersity and molecular weight on the O
 rder-Disorder Transition in Poly(3-hexylthiophene”\nJ. Phys. Chem. Lett.
  2014\, 5\, 2742\n\nBio: Professor Anna Köhler holds the Chair of Experim
 ental Physics II at the University of Bayreuth.\nHer research is concerned
  with photophysical processes in organic semiconductors. Her research grou
 p focusses in particular on the processes of energy and charge transfer in
  singlet and triplet excited states\, the exciton dissociation mechanism a
 nd intermolecular/interchain interactions. She has published more than 100
  papers\, several book chapter and one textbook.\nAnna Köhler received he
 r PhD in 1996 from the University of Cambridge\, UK\, where she continued 
 her research funded through Research Fellowships by Peterhouse and by the 
 Royal Society. In 2003 she was appointed Professor at the University of Po
 tsdam\, Germany\, from where she moved to the Department of Physics at the
  University of Bayreuth\, Germany\, in 2007.\n 
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
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