Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend.
Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend.
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DOI：
10.1038/srep26832
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发表时间：
2016-05-26
影响因子：
4.6
通讯作者：
Neher D
中科院分区：
文献类型：
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作者：
Kurpiers J;Neher D
自由电荷的减少是限制太阳能电池性能的关键过程。对于低迁移率材料，例如有机半导体，非成对复合（NGR）的动力学与电荷的运动密切相关。由于这些材料具有显著的无序性，光生载流子在非均匀加宽的态密度分布中的热化是不可避免的过程。尽管NGR具有普遍重要性，但有关NGR在完全有机太阳能电池中的动力学知识相当有限。我们采用时间延迟收集场（TDCF）实验研究高性能聚合物：富勒烯共混物PCDTBT：PCBM中光生电荷的复合。NGR在这种无定形共混物的散装被证明是高度分散的，在整个时间尺度上的重组系数的连续减少，直到所有的电荷载流子被提取或重组。快速，接触介导的复合被确定为一个额外的损失通道，如果没有适当考虑，将错误地建议一个明显的场依赖的电荷产生。这些发现与由有序共混物（例如P3HT：PCBM）制成的光伏器件上的TDCF实验的结果形成鲜明对比，其中非色散复合被证明在应用相关条件下主导电荷载流子动力学。
Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions.