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SUMMARY:Highly Efficient Organic Devices - Professor Karl Leo\, Institut f
 ür Angewandte Photophysik\, Technische Universität Dresden\, 01062 Dres
 den\, Germany
DTSTART:20100128T150000Z
DTEND:20100128T160000Z
UID:TALK22473@talks.cam.ac.uk
CONTACT:Dr. Z Chen
DESCRIPTION:Organic semiconductors with conjugated electron system are cur
 rently intensively investigated for optoelectronic applications. This inte
 rest is spurred by novel devices such as organic light-emitting diodes (OL
 ED)\, and organic solar cells. For both devices\, high efficiency is a key
  parameter for many applications. I this talk\, I will discuss some of the
  recent progress on highly efficient OLED and solar cells\, in particular 
 results using doped transport layers /1/: Surprisingly\, doping (for raisi
 ng the conductivity) has been largely ignored till now in organic devices\
 , in contrast to classical silicon technology where controlled n- and p-ty
 pe doping has always been a standard technique needed for virtually all de
 vices.\nThe concept of molecular doping allowed to realize green OLED devi
 ces with the highest efficiencies reported so far /2/\, well exceeding the
  efficiency of current inorganic GaN LED! The devices were pin-devices whe
 re the emitting layer is embedded between a p-doped hole transport layer a
 nd an n-doped electron transport layers. It has been shown that these pin-
 structures can also achieve extremely long lifetimes. White OLED have rece
 ntly achieved very high efficiencies of 90lm/W /3/\, significantly higher 
 than fluorescent tubes\, opening the path to a new form of high-efficiency
  area lighting devices.\nThe doping concepts can be applied in organic sol
 ar cells as well. Here\, the use of electrically doped transport layers is
  helpful for an optimized optical design since it yields large freedom in 
 the choice of window layer thickness\, this making it easy to put the abso
 rber layers in the electric field maximum in the cavity. Also\, doped laye
 rs are a key point in efficient charge recombination junctions for tandem 
 solar cells: It has been shown that a pn-junction is an excellent recombin
 ation contact causing very small voltage loss. Recently\, we have achieved
  solar cells with certified efficiency exceeding 6% on larger area.\n/1/ K
 . Walzer\, B. Maennig\, M. Pfeiffer M\, K. Leo\, Chem. Rev. 107\, 1233 (20
 09)\n/2/ G. He\, M. Pfeiffer\, K. Leo\, M. Hofmann\, J. Birnstock\, R. Pud
 zich\, J. Salbeck\, Appl. Phys. Lett. 85\, 3911 (2004).\n/3/ S. Reineke\, 
 F. Lindner\, G. Schwartz\, N. Seidler\, K. Walzer\, B. Lüssem\, Nature 4
 59\, 234 (2009).\n*: I would like thank Jan Blochwitz-Nimoth\, Torsten Fri
 tz\, Kentaro Harada\, Gufeng He\, Qiang Huang\, Björn Luessem\, Rico Meer
 heim\, Martin Pfeiffer\, Sebastian Reineke\, Moritz Riede\, Rico Schüppe
 l\, Gregor Schwartz\, Karsten Walzer\, Ansgar Werner\, Xiang Zhou\, and ma
 ny others for their participation in this work.
LOCATION:Small Lecture Theatre\, Cavendish Laboratory\, Department of Phys
 ics
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