Hot exciton dissociation in polymer solar cells
Hot exciton dissociation in polymer solar cells
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DOI：
10.1038/nmat3502
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发表时间：
2013-01-01
期刊：
影响因子：
41.2
通讯作者：
Lanzani, G.
中科院分区：
文献类型：
--
作者：
Grancini, G.;Maiuri, M.;Lanzani, G.
在全有机本体异质结太阳能电池中的光伏转换的标准图片预测初始激发在热化之后在供体/受体界面处解离（1 - 12）。因此，在带隙以上激发时，多余的光子能量通过内部耗散而迅速损失（2，3，11，13 - 16）。在这里，我们直接针对一个有效的低带隙聚合物/PC60BM系统的界面物理。激子分裂发生在第一个50 fs，创建界面电荷转移态（CTS）和极化子物种。在高能量激发下，较高的单重态转化为热的界面CTS，有效地促进了自由极化子的产生。我们合理化这些发现的热CTS相对于放松的，这提高了在第一个200 fs的电荷解离的概率的离域度较高。因此，热CTS解离产生电荷产生产率的总体增加。
The standard picture of photovoltaic conversion in all-organic bulk heterojunction solar cells predicts that the initial excitation dissociates at the donor/acceptor interface after thermalization(1-12). Accordingly, on above-gap excitation, the excess photon energy is quickly lost by internal dissipation(2,3,11,13-16). Here we directly target the interfacial physics of an efficient low-bandgap polymer /PC60BM system. Exciton splitting occurs within the first 50 fs, creating both interfacial charge transfer states (CTSs) and polaron species. On high-energy excitation, higher-lying singlet states convert into hot interfacial CTSs that effectively contribute to free-polaron generation. We rationalize these findings in terms of a higher degree of delocalization of the hot CTSs with respect to the relaxed ones, which enhances the probability of charge dissociation in the first 200 fs. Thus, the hot CTS dissociation produces an overall increase in the charge generation yield.