Resolving Donor-Acceptor Interfaces and Charge Carrier Energy Levels of Organic Semiconductors with Polar Side Chains
Resolving Donor-Acceptor Interfaces and Charge Carrier Energy Levels of Organic Semiconductors with Polar Side Chains
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DOI：
10.1002/adfm.202004799
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发表时间：
2020-09-06
影响因子：
19
通讯作者：
Havenith, Remco W. A.
中科院分区：
文献类型：
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作者：
Alessandri, Riccardo;Sami, Selim;Havenith, Remco W. A.
由带有极性侧链的分子组成的有机半导体由于其增强的介电常数而被提出作为克服有机光致变色的限制的潜在候选者。然而，在光伏器件中引入这样的极性分子尚未导致更高的效率。极性侧链对有机半导体的电子和结构性质的影响的微观理解是最重要的合理化他们的效果。在这里，这样的侧链上的整体异质结的整体形态，在施主-受体（DA）界面的分子构型，和电荷载流子的能级的影响进行了研究。所使用的多尺度建模方法可以解决DA接口与原子分辨率，同时考虑到大规模的自组织过程中发生的有机薄膜的处理。极性富勒烯为基础的共混物进行了比较，充分研究的参考系统，聚（3-己基-噻吩）（P3 HT）：苯基-C-61-丁酸甲酯（PCBM）。在类似的分子支架上引入极性侧链不影响DA界面处的分子取向;然而，发现这种取向受加工条件和聚合物分子量的影响。相反，发现极性侧链对有机共混物的电荷载流子能级有相当大的影响，导致这些能级的静电诱导加宽。
Organic semiconductors consisting of molecules bearing polar side chains have been proposed as potential candidates to overcome the limitations of organic photovoltaics owing to their enhanced dielectric constant. However, introducing such polar molecules in photovoltaic devices has not yet resulted in higher efficiencies. A microscopic understanding of the impact of polar side chains on electronic and structural properties of organic semiconductors is paramount to rationalize their effect. Here, the impact of such side chains on bulk heterojunction overall morphology, molecular configurations at donor-acceptor (DA) interfaces, and charge carrier energy levels is investigated. The multiscale modeling approach used allows to resolve DA interfaces with atomistic resolution while taking into account the large-scale self-organization process which takes place during the processing of an organic thin film. The polar fullerene-based blends are compared to the well-studied reference system, poly(3-hexyl-thiophene) (P3HT):phenyl-C-61-butyric acid methyl ester (PCBM). Introduction of polar side chains on a similar molecular scaffold does not affect molecular orientations at the DA interfaces; such orientations are, however, found to be affected by processing conditions and polymer molecular weight. Polar side chains, instead, are found to impact considerably the charge carrier energy levels of the organic blend, causing electrostatic-induced broadening of these levels.