Liirò-Peluso Letizia, Wrigley James, Amabilino David B, Beton Peter H
The GSK Carbon Neutral Laboratories for Sustainable Chemistry, School of Chemistry, University of Nottingham, Triumph Road, Nottingham NG7 2TU, U.K.
School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, U.K.
ACS Appl Nano Mater. 2022 Oct 28;5(10):13794-13804. doi: 10.1021/acsanm.2c01399. Epub 2022 Jun 17.
The efficiency of organic bulk-heterojunction (BHJ) solar cells depends greatly on both the bulk and surface structure of the nanostructured bicontinuous interpenetrating network of materials, known as the active layer. The morphology of the top layer of a coated film is often resolved at the scale of a few nanometers, but fine details of the domains and the order within them are more difficult to identify. Here, we report a high-resolution atomic force microscopy (AFM) investigation of various stoichiometries of the well-studied poly(3-hexylthiophene):[6,6]-phenyl C butyric acid methyl ester (P3HT:PCBM) active layer mixture. Images of the surface were obtained using AC-mode AFM exciting higher-order resonance frequencies of a standard silicon probe, a promising technique for acquiring real-space images of organic-based thin films with nanoscale and even submolecular resolution. We provide firm evidence of the nanoscale organization of the P3HT polymer and of the P3HT:PCBM stoichiometric mixtures at the surface-air interface of the BHJ architecture. Our study shows the characteristic periodicity of the regioregular P3HT identified in the nanoscale domain areas with submolecular resolution. Such areas are then distorted in place when adding different quantities of PCBM forming stoichiometric mixtures. When the samples were exposed to ambient light, the morphologies were very different, and submolecular resolution was not achieved. This approach is shown to provide a precise view of the active layer's nanostructure and will be useful for studies of other materials as a function of various parameters, with particular attention to the role of the acceptor in tuning morphology for understanding optimum performance in organic photovoltaic devices.
有机本体异质结（BHJ）太阳能电池的效率在很大程度上取决于材料的纳米结构双连续互穿网络（即活性层）的本体结构和表面结构。涂膜顶层的形态通常在几纳米的尺度上得到解析，但畴的精细细节及其内部的有序性更难识别。在此，我们报告了对研究充分的聚（3-己基噻吩）：[6,6]-苯基丁酸甲酯（P3HT:PCBM）活性层混合物的各种化学计量比进行的高分辨率原子力显微镜（AFM）研究。使用交流模式AFM激发标准硅探针的高阶共振频率获得了表面图像，这是一种用于获取具有纳米级甚至亚分子分辨率的有机基薄膜实空间图像的有前景的技术。我们提供了P3HT聚合物以及P3HT:PCBM化学计量混合物在BHJ结构的表面-空气界面处纳米级组织的有力证据。我们的研究显示了在具有亚分子分辨率的纳米级畴区域中识别出的区域规整P3HT的特征周期性。当添加不同量的PCBM形成化学计量混合物时，这些区域会在原位发生变形。当样品暴露于环境光时，形态非常不同，并且未实现亚分子分辨率。结果表明，这种方法能够提供活性层纳米结构的精确视图，对于研究其他材料作为各种参数的函数将是有用的，尤其关注受体在调节形态以理解有机光伏器件的最佳性能方面的作用。
