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SUMMARY:Self-assembling Organic Nanostructures for Solar Energy Conversion
  - Professor Michael R. Wasielewski\, Northwestern University
DTSTART:20180315T160000Z
DTEND:20180315T170000Z
UID:TALK100612@talks.cam.ac.uk
CONTACT:Sharon Connor
DESCRIPTION:Self-assembly of small electron donor-acceptor (D-A) molecules
  into discrete and monodisperse nanostructures provides geometrically defi
 ned platforms to emulate the photo-induced electron transfer processes in 
 photosynthesis. Organization of molecules by this thermodynamically driven
  method can result in architectures with unique inter-chromophore relation
 ships that are otherwise difficult to realize by conventional covalent syn
 thesis. In particular\, -stacked D-A dyads and triads can afford ordered a
 nd segregated D/A domains through which photo-generated holes and electron
 s can be further separated and rapidly transported to electrodes in photov
 oltaics or to catalysts for solar fuels formation. We have developed assem
 bly strategies based on controlled -stacking and bio-inspired guanine quad
 ruplexes\, which demonstrate that photo-induced charge separation can take
  place within covalent chromophoric redox partners followed by transport o
 f photo-generated holes and electrons independently through well-ordered\,
  segregated molecular charge conduits (Figure 1).\n\n\n\n\nWe are also dev
 eloping robust organic chromophores that undergo singlet fission (SF)\, th
 e spontaneous down-conversion of a singlet exciton to two triplet excitons
  (Figure 2)\, using guidance from electronic structure calculations to ass
 ure the requisite relationships between molecular singlet and triplet exci
 ton energies. We are preparing hierarchical assemblies of these chromophor
 es\, starting from covalent dimers\, then developing supramolecular assemb
 lies\, and engineered crystalline materials to investigate SF in bulk\, or
 dered organic materials. We are using time-resolved optical and EPR spectr
 oscopy to characterize the SF mechanism and the factors that determine its
  efficiency. We will present results on the role of charge transfer and qu
 intet states in enabling SF in organic materials.
LOCATION:Pfizer Lecture Theatre\, Department of Chemistry\, Lensfield Road
 \, Cambridge
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