[Todos] Seminario DQIAQF - INQUIMAE, lunes 23 y martes 24 de mayo - 13 hs.

[andrea en qi.fcen.uba.ar]

Seminario DQIAQF - INQUIMAE,  lunes 23 de Mayo - 13 hs.

Aula de Seminarios INQUIMAE - DQIAQF
Facultad de Ciencias Exactas y Naturales
Ciudad Universitaria - Pab. 2  -  Piso 3

Gerald Meyer
Professor of Chemistry
Department of Chemistry Johns Hopkins University

“ELECTRON TRANSFER IN DYE-SENSITIZED SOLAR CELLS”

Abstract
Recently an order of magnitude increase in solar energy conversion
efficiencies from dye-sensitized photovoltaic cells has been realized.
These solar cells are based upon mesoporous thin films of nanocrystalline
(anatase) TiO2 sensitized to visible light with inorganic coordination
compounds that serve as dyes.  Under simulated sunlight conditions,
solar-to-electrical power conversion efficiencies of 11.47% have been
confirmed. The sensitized materials have an enormous surface area, a long
effective pathlength, and a high photoconductivity that affords both
spectroscopic and photoelectrochemical characterization of interfacial
charge transfer processes.

In this presentation an overview of our recent experimental studies of
solar energy conversion, materials processing, chemical bond formation,
and interfacial charge transfer will be presented.   Specific topics
include excited state, interfacial and intermolecular electron transfer at
sensitized semiconductor interfaces.  Recent data on electric field
effects at molecular-semiconductor interfaces as well as the mechanisms of
I-I bond formation will be presented.  These studies were designed to
provide insights into the factors that control electron transfer at
semiconductor interfaces with implications that extend beyond electrical
power generation to the growing research field of solar fuel production.



Biographical

Professor Gerald Meyer received his Ph.D. in chemistry at the University
of Wisconsin at Madison in 1989 under the direction of Professor Arthur B.
Ellis.  He then worked as a post-doctoral research associate at University
of North Carolina at Chapel Hill working with Professor Thomas J. Meyer
before joining the faculty at Johns Hopkins University in 1991 where he is
now the Bernard N. Baker Professor of Chemistry.   His research interests
include inorganic coordination chemistry, electron transfer, excited
states, photocatalysis, photoelectrochemistry, and solar energy
conversion.














Seminario DQIAQF - INQUIMAE,  Martes 24 de Mayo - 13 hs.

Aula de Seminarios INQUIMAE - DQIAQF
Facultad de Ciencias Exactas y Naturales
Ciudad Universitaria - Pab. 2  -  Piso 3


Luisa De Cola
Physikalisches Institut, and CeNTech, University of Münster, Mendelstrasse
, D-48149 Muenster (decola en uni-muenster.de)

“LUMINESCENT SOFT AND HARD ASSEMBLIES”



Electroluminescent metal complexes have been widely investigated for their
potential use as dopant in Organig Light Emitting Devices, OLEDs, and when
charged in Light Emitting Electrochemical Cells, LEECs. In this we will
discuss the formation of soft [1,2] and hard crystalline luminescent
systems [3-5]. Tuning the design of the metal complexes based mainly on
iridium and platinum metal ions and containing phenylpyridine, pyridine,
and pyridine azoles, or dinegative tridentate N-N-N ligands we are able to
control the degree of intermolecular interactions leading to the formation
of fibers and gels, or crystalline materials. In particular the
possibility to promote aggregation and the new emission properties rising
from the formation of the assemblies, such as enhancement of the emission,
will be discussed in two examples. A non-luminescent platinum complex,
becoming extremely emitting (90% emission quantum yields) upon
aggregation, is described. The Pt(II) complex can assemble in fibers or
even form luminescent gels. The material has been used to construct
electroluminescent devices [1]. The aggregation can also be prevented and
other neutral Pt(II) complexes have been prepared and used for OLED
materials. Finally crystalline iridium complexes (left figure) will be
discussed and porous structures have been obtained with some of them. In
particular, in one of the described systems, two luminescent iridium
complexes, possessing different emission colors, and complementary charges
are employed to form complex salts and non covalent linked crystalline
porous photo- and electroactive framework [3]. The strategy described can
be extended to many photo- and electroresponsive ionic transition metal
complexes and could constitute the future generation of organometallic
zeolite-like structures. The modulation of their properties with
appropriate guests will be then discussed.

 [1]  C. A. Strassert, C.-H. Chien, M. D. Galvez Lopez, D. Kourkoulos, D.
Hertel, K. Meerholz, L. De Cola Angew. Chem. Int. Ed., 2011, 50, 946.
[2]  M. Mydlak, M. Mauro, F. Polo, M. Felicetti, J. Leonhardt, G. Diener,
L. De Cola, C.A. Strassert submitted.
[3]  M. Mauro, K. C. Schuermann, R. Prétôt, A. Hafner, P. Mercandelli, A.
Sironi, L. De Cola  Angew. Chem. Int. Ed., 2010, 49, 1222.
[4]  N. Darmawan, R. Fröhlich, L. De Cola, submitted.
[5]  E. Quartapelle Procopio, M. Mauro, M. Panigati, D. Donghi, P.
Mercandelli, A. Sironi, G. D´Alfonso, L. De Cola J. Am. Chem. Soc., 2010,
132, 14397.