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SUMMARY:Prof. Natalie Banerji : Charge Carriers in Organic Semiconductors
DTSTART:20251205T140000
DTEND:20251205T150000
DTSTAMP:20261004T210020Z
UID:aa03b7a65b81de948cb472bddd367f09b4eb0c4801628c0e0f7d266c
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Natalie Banerji\,\nDpt of Chemistry\, Biochemistry and P
 harmaceutical\,\nUniversity of Bern\, CH\nAbstract : Doping of organic sem
 iconductor films (chemically\, electrochemically or by light absorption) e
 nhances their conductivity for applications in organic electronics\, photo
 voltaics\, thermoelectrics and bioelectronics. However\, much remains to b
 e learnt about the properties of the conductive charges in order to optimi
 ze the design of the materials. We use ultrafast spectroscopic techniques\
 , such as transient absorption (TA) and time-domain terahertz (TD-THz) spe
 ctroscopies\, to investigate charge carriers in organic semiconductors. Wh
 ile femtosecond TA measurements bring insights to the nature and evolution
  of photoexcited species\, we use TD-THz spectroscopy to gain information 
 about the charge transport properties at the nanoscale. Processes of inter
 est include charge generation in organic photovoltaics (OPVs)\, electroche
 mical doping in organic electrochemical transistors (OECTs) and generation
  of highly conductive polymer films by chemical doping. Recently\, anion-e
 xchange doping\, whereby the dopant counterion is replaced by inorganic an
 ions by exposure of a p-doped film\nto an electrolyte\, has been demonstra
 ted as an effective way to overcome the limitations of chemical dopants in
  terms of bulkiness\, stability and energetics. In parallel\, the success 
 of OECTs has fostered the development of better organic mixed ionic-electr
 onic conductors\, notably by replacing the commonly used alkyl sidechains 
 of conjugated polymers with more polar oligoether sidechains. Inspired by 
 the similar counterion nature of organic thin films doped either electroch
 emically or by anion exchange\, we combine here the two concepts and find 
 that anion exchange leads to enhanced conductivity in polythiophene and th
 ienothiophene polymers with oligoether side chains (over 2000 S cm-1). To 
 elucidate the origin of this high conductivity\, we combine spectroscopic 
 characterization with long-range (fourpoint-probe) and short-range (terahe
 rtz) conductivity measurements. We show that the highly\nconductive sample
 s sustain high charge densities without any drop in conductivity and witho
 ut any compromise on charge mobility. Moreover\, no loss in conductivity o
 ccurs when going from nanometer to millimeter distances\, demonstrating hi
 ghly effective charge transport over multiple length scales.\n\nBio : Prof
 essor Natalie Banerji is currently a Full Professor of Physical Chemistry 
 at the University of Bern. Her research interests include the study of org
 anic and hybrid materials\nusing ultrafast spectroscopic techniques\, in v
 iew of solar cell and bioelectronic applications. She studied Chemistry at
  the University of Geneva and obtained her Ph.D. in Physical Chemistry in 
 2009\, under the supervision of Prof. Eric Vauthey. She then moved to the 
 University of California in Santa Barbara (USA)\, to work on organic solar
  cells during a post-doctoral stay with Nobel Laureate Prof. Alan J. Heege
 r (2009-2011). In 2011\, she started her independent research career in Sw
 itzerland at the Ecole Polytechnique Férérale de Lausanne (EPFL) with an
  Ambizione Fellowship by the Swiss National Science Foundation (SNSF). She
  obtained an SNSF-Professorship at the University of Fribourg (Switzerland
 ) in 2014\, and was subsequently nominated tenured Associate Professor in 
 2015. She was President of the Chemistry Department in Fribourg form 2016-
 2017 and moved to Bern in 2017. In 2015\, she obtained the Grammaticakis-N
 eumann Prize (Swiss Chemical Society) and in 2016\, she was awarded an ERC
  Starting Grant. She is currently also part of the Swiss Research Council 
 (Chair of Project Funding Committee) and Associate Editor of ACS Materials
  Letters.\n 
LOCATION:Tseuzier https://plan.epfl.ch/?room==I17%204%20K2 https://epfl.zo
 om.us/j/65378030944
STATUS:CONFIRMED
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