Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes

Understanding the charge-separation mechanism in organic photovoltaic cells (OPVs) could facilitate optimization of their overall efficiency. Here we report the time dependence of the separation of photogenerated electron hole pairs across the donor-acceptor heterojunction in OPV model systems. By t...

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Bibliographic Details
Published in:	Science (American Association for the Advancement of Science) Vol. 343; no. 6170; p. 512
Main Authors:	Gélinas, Simon, Rao, Akshay, Kumar, Abhishek, Smith, Samuel L, Chin, Alex W, Clark, Jenny, van der Poll, Tom S, Bazan, Guillermo C, Friend, Richard H
Format:	Journal Article
Language:	English
Published:	United States 31.01.2014
ISSN:	1095-9203, 1095-9203
Online Access:	Get more information
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Summary:	Understanding the charge-separation mechanism in organic photovoltaic cells (OPVs) could facilitate optimization of their overall efficiency. Here we report the time dependence of the separation of photogenerated electron hole pairs across the donor-acceptor heterojunction in OPV model systems. By tracking the modulation of the optical absorption due to the electric field generated between the charges, we measure ~200 millielectron volts of electrostatic energy arising from electron-hole separation within 40 femtoseconds of excitation, corresponding to a charge separation distance of at least 4 nanometers. At this separation, the residual Coulomb attraction between charges is at or below thermal energies, so that electron and hole separate freely. This early time behavior is consistent with charge separation through access to delocalized π-electron states in ordered regions of the fullerene acceptor material.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1095-9203 1095-9203
DOI:	10.1126/science.1246249