Ultrafast Long-Range Charge Separation in Organic Semiconductor Photovoltaic Diodes
Ultrafast Long-Range Charge Separation in Organic Semiconductor Photovoltaic Diodes
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DOI：
10.1126/science.1246249
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发表时间：
2014-01-31
期刊：
影响因子：
56.9
通讯作者：
Friend, Richard H.
中科院分区：
文献类型：
--
作者：
Gelinas, Simon;Rao, Akshay;Friend, Richard H.
了解有机光伏电池（OPV）中的电荷分离机制有助于优化其整体效率。在这里，我们报告的时间依赖性的光生电子-空穴对的分离跨越的施主-受主异质结的OPV模型系统。通过跟踪由于电荷之间产生的电场引起的光吸收的调制，我们在40飞秒激发内测量了类似于200毫电子伏的静电能量，该静电能量由电子-空穴分离产生，对应于至少4纳米的电荷分离距离。在这种分离下，电荷之间的剩余库仑吸引力等于或低于热能，使得电子和空穴自由分离。这种早期行为与通过在富勒烯受体材料的有序区域中获得离域π电子态的电荷分离一致。
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 similar to 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 pi-electron states in ordered regions of the fullerene acceptor material.