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SUMMARY:Towards a quantitative analysis of core-level and valence photoemi
 ssion spectra of dye-sensitized solar cell interfaces - Dr Feliciano Giust
 ino (University of Oxford)
DTSTART:20130314T141500Z
DTEND:20130314T151500Z
UID:TALK43352@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:Functional interfaces have acquired a primary role in many are
 as of science and technology\, ranging from photovoltaics and photocatalys
 is to electronics and biosensing. A fundamental property of functional int
 erfaces is the alignment of the quasiparticle energy levels between the tw
 o materials. Such alignment underpins a variety of complex phenomena such 
 as charge-transfer doping\, carrier injection\, and exciton dynamics. In t
 he context of solar energy technology the level alignment determines the a
 bility of the interface to transfer energy from a donor to an acceptor by 
 exchanging photoexcited charges. While the physics of the energy-level ali
 gnment at conventional semiconductor heterojunctions is currently well est
 ablished\, little is known about functional interfaces involving metal oxi
 des and soft materials such as polymers and light-harvesting complexes. He
 re I will review our recent activity in the computational modelling of TiO
 2 interfaces for dye-sensitized solar cells\, and of experimental probes s
 uch as X-ray photoemission spectroscopy and ultraviolet photoemission spec
 troscopy. In this area the first challenge that we have to face is to dete
 rmine the structure of the interface at the atomic scale. Standard optimiz
 ation techniques are inadequate for this task due to the large number of p
 ossible interfacial morphologies. I will argue that a possible way forward
  is to build interface models by reverse-engineering experimental data usi
 ng first-principles computational spectroscopy. This notion will be illust
 rated by discussing core-level photoemission spectra at the TiO2/N3 interf
 ace. The second challenge is the development of robust computational metho
 ds for studying the energy-level alignment at the interface. Standard dens
 ity-functional techniques are rarely in quantitative agreement with photoe
 mission data\, and in some cases they fail to correctly describe the inter
 facial charge transfer. In order to perform a quantitative comparison with
  experiment it is important to develop a comprehensive theory of electron 
 removal and addition processes in molecules and solids. Such theory needs 
 to capture the complex interplay of image charges\, thermal broadening\, a
 nd configurational disorder. Here I will discuss a recent proposal of our 
 group for addressing this challenge.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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