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SUMMARY:Progress in making organic solar cells highly efficient and stable
  - Prof. Michael McGehee\, Department of Materials Science and Engineering
 \, Stanford University\, USA
DTSTART:20130531T133000Z
DTEND:20130531T143000Z
UID:TALK45589@talks.cam.ac.uk
CONTACT:Dr. Girish Lakhwani
DESCRIPTION:Some of the key questions regarding polymer solar cells are wh
 y certain bulkheterojunctions have internal quantum efficiencies higher th
 an 90%\, what is the optimal morphology and why fullerenes are by far the 
 best electronic acceptors. We will show that in several highly efficient s
 olar cells there is a three-phase morphology in which there are pure regio
 ns of polymer and fullerenes along with a mixed region. We will show that 
 there are energetic offsets that push electrons and holes out of the mixed
  region and into the pure region. One can control the size and composition
  of the phases by adjusting factors such as the regioregularity and molecu
 lar weight of the polymer\, the polymers sidechains\, the donor:acceptor r
 atio\, the choice of fullerenes\, the use of processing additives and anne
 aling conditions. We will show how one can decide what to adjust to get th
 e ideal morphology and thereby obtain high energy conversion efficiency in
  solar cells.  We will also discuss the mechanisms of degradation and poly
 mer solar cells and how the lifetime can be extended.
LOCATION:Kapitza Building Seminar Room\, Cavendish Laboratory\, Department
  of Physics
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