Elimination of charge carrier trapping in diluted semiconductors.
In 1962, Mark and Helfrich demonstrated that the current in a semiconductor containing traps is reduced by N/Nt(r), with N the amount of transport sites, Nt the amount of traps and r a number that depends on the trap energy distribution. For r > 1, the possibility opens that trapping effects can be nearly eliminated when N and Nt are simultaneously reduced. Solution-processed conjugated polymers are an excellent model system to test this hypothesis, because they can be easily diluted by blending them with a high-bandgap semiconductor. We demonstrate that in conjugated polymer blends with 10% active semiconductor and 90% high-bandgap host, the typical strong electron trapping can be effectively eliminated. As a result we were able to fabricate polymer light-emitting diodes with balanced electron and hole transport and reduced non-radiative trap-assisted recombination, leading to a doubling of their efficiency at nearly ten times lower material costs.
Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.|Dutch Polymer Institute, PO Box 902, 5600 AX, Eindhoven, The Netherlands.
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0000-0003-1955-3492
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Abbaszadeh
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Kunz
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Wetzelaer
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
J J
JJ
Michels
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Crăciun
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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K
Koynov
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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I
Lieberwirth
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Blom