Effects of Molecular Orientation in Acceptor-Donor Interfaces between Pentacene and C60 and Diels-Alder Adduct Formation at the Molecular Interface
Effects of Molecular Orientation in Acceptor-Donor Interfaces between Pentacene and C60 and Diels-Alder Adduct Formation at the Molecular Interface
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DOI：
10.1002/admi.201500452
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发表时间：
2016-04-08
影响因子：
5.4
通讯作者：
Witte, Gregor
中科院分区：
文献类型：
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作者：
Breuer, Tobias;Karthaeuser, Andrea;Witte, Gregor
并五苯和巴克敏斯特-富勒烯（C-60）之间的界面作为有机太阳能电池的低聚模型体系而备受关注。由于这种实现中的实际设备特性关键地由界面结构控制，因此必须在分子水平上对该界面进行详细研究。本研究分析了并五苯分子在高有序结晶底层的取向对这种内部界面特性的影响。结果表明，对于垂直取向的并五苯，界面结构是由温度控制的C-60分子向并五苯阶梯边缘的扩散驱动的。对于底层的并五苯，没有观察到阶梯边缘的装饰，但对并五苯层的润湿性增强。此外，利用NEXAFS光谱分析了界面对插层和重定向的稳定性，表明界面上并五烯分子的取向保持不变。相反，通过在C-60和并五烯之间形成Diels-Alder加合物，可以观察到分子实体发生化学修饰的强烈迹象。最后表明，C-60仅在垂直取向的五苯上形成较厚的结晶岛，而在横置的五苯上形成非晶膜。
Interfaces between pentacene and Buckminster-fullerene (C-60) have attracted interest due to their application as oligomeric model system for organic solar cells. As the actual device characteristics in such implementations are crucially controlled by the interface structure, detailed investigations of this interface on a molecular level are mandatory. In this study, the influence of the orientation of the pentacene molecules in highly ordered crystalline bottom layers on the characteristics of such internal interfaces is analyzed. It has been shown that the interface structure is driven by temperature-controlled diffusion of C-60 molecules to the pentacene step edges in the case of uprightly oriented pentacene. For lying pentacene in the bottom layer, no step-edge decoration is observed while the wetting of the pentacene layer is enhanced. Furthermore, the stability of the interface against intercalation and reorientation has been analyzed by means of NEXAFS spectroscopy, showing that the orientation of the pentacene molecules at the interface remains unchanged. Instead, strong indication for chemical modification of the molecular entities by the formation of Diels-Alder adducts between C-60 and pentacene is observed. Finally, it is shown that C-60 forms crystalline islands in thicker films only on top of uprightly oriented pentacene while rather amorphous films are formed on lying pentacene.