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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 / N t r , with N the amount of transport sites, N t the amount of traps and r a number that depends on the trap energy distribution. For r > 1, the possibility opens that trapping effects...

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Bibliographic Details
Published in:Nature materials 2016-06, Vol.15 (6), p.628-633
Main Authors: Abbaszadeh, D., Kunz, A., Wetzelaer, G. A. H., Michels, J. J., Crăciun, N. I., Koynov, K., Lieberwirth, I., Blom, P. W. M.
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Language:English
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Summary:In 1962, Mark and Helfrich demonstrated that the current in a semiconductor containing traps is reduced by N / N t r , with N the amount of transport sites, N t 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 N t 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. By diluting conjugated polymers in high-bandgap host matrices it is shown that electron trapping effects can be significantly reduced. This approach is used to fabricate polymer LEDs with enhanced efficiency and reduced fabrication costs.
ISSN:1476-1122
1476-4660
DOI:10.1038/nmat4626