Department of Chemistry, University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland.
Photochemical Dynamics Group, Institute of Chemical Sciences &Engineering and Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne (EPFL), SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland.
Nat Commun. 2016 Sep 2;7:12556. doi: 10.1038/ncomms12556.
There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs-whether they will dissociate to free charges or geminately recombine-is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%.
在用于有机太阳能电池的施主-受主共混物中，自由电荷是如何产生的，这一直存在争议，而这些共混物通常具有复杂的相形态，其中施主和受主材料的混合相和纯相共存。在这里，我们基于在不存在和存在外加电场的情况下获得的斯塔克效应光谱数据解决了这个问题。我们结合文献中发现的相反观点，明确证明了光生电子-空穴对的命运——它们是否会解离成自由电荷或复合——是在超快时间内决定的，尽管它们的实际空间分离可能要慢得多。我们的见解对于进一步发展有机太阳能电池的合理材料设计和处理方法非常重要，有助于实现其作为无铅第三代能源技术的预期承诺，该技术可以达到超过 10%的效率。
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