Identifying the Nature of Charge Recombination in Organic Solar Cells from Charge‐Transfer State Electroluminescence |
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| Authors: | Gert‐Jan A. H. Wetzelaer Martijn Kuik Paul W. M. Blom |
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| Affiliation: | 1. Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands;2. Dutch Polymer Institute, PO Box 902, 5600 AX Eindhoven, The Netherlands;3. TNO/Holst Centre, High Tech Campus 31, 5605 KN Eindhoven, The Netherlands |
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| Abstract: | Charge‐transfer (CT) state electroluminescence is investigated in several polymer:fullerene bulk heterojunction solar cells. The ideality factor of the electroluminescence reveals that the CT emission in polymer:fullerene solar cells originates from free‐carrier bimolecular recombination at the donor‐acceptor interface, rather than a charge‐trap‐mediated process. The fingerprint of the presence of nonradiative trap‐assisted recombination, a voltage‐dependent CT electroluminescence quantum efficiency, is only observed for the P3HT:PCBM system, which is explained by a reduction of the competing bimolecular recombination rate. These results are in agreement with measurements of the illumination‐intensity dependence of the open‐circuit voltage. |
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| Keywords: | charge‐carrier recombination charge‐transfer states electroluminescence organic solar cells |
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