Oleamide as a self-assembled cathode buffer layer for polymer solar cells: the role of the terminal group on the function of the surfactant
Oleamide as a self-assembled cathode buffer layer for polymer solar cells: the role of the terminal group on the function of the surfactant
复制标题
油酰胺作为聚合物太阳能电池自组装阴极缓冲层：端基对表面活性剂功能的影响
DOI：
10.1039/c2jm35199d
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发表时间：
2012-10
影响因子：
--
通讯作者：
Yang, Shangfeng
中科院分区：
文献类型：
--
作者：
Zhang, Wenfeng;Wang, Haitao;Chen, Boxue;Bi, Xianghong;Venkatesan, Swaminathan;Qiao, Qiquan;Yang, Shangfeng
通过在 P3HT:PCBM 光敏层中掺杂，然后进行自组装，首次将两亲性表面活性剂油酰胺作为新型阴极缓冲层 (CBL) 纳入 P3HT:PCBM 本体异质结聚合物太阳能电池 (BHJ-PSC) 中。在最佳油酰胺掺杂比例为 2.5% 时，退火后的 P3HT:PCBM/油酰胺 BHJ-PSC 器件的功率转换效率 (PCE) 提高了约 28%，这主要是由于填充因子 (FF) 增加了约 22%。通过透射电子显微镜（TEM）、原子力显微镜（AFM）和扫描开尔文探针显微镜（SKPM）研究了掺有油酰胺的 P3HT:PCBM 光活性薄膜的表面形貌，揭示了最初掺杂在 P3HT:PCBM 层中的油酰胺分子可能会发生自组装并迁移到 P3HT:PCBM 层的顶面，从而形成作为界面偶极层的阴极缓冲层（CBL）位于光活性层和Al阴极电极之间。这种油酰胺界面偶极层降低了Al的功函数，因此Al的功函数与PCBM受体的LUMO能级之间的能级偏移减小，有利于Al阴极的电子提取。此外，根据 X 射线衍射 (XRD) 表征，我们发现掺入油酰胺后 P3HT 的结晶度几乎没有变化。值得注意的是，这种现象与之前报道的类似表面活性剂油酸的情况完全不同，油酸掺杂在P3HT:PCBM光活性层中，由于P3HT结晶度的增加而导致效率提高，这表明表面活性剂的端基对其在P3HT:PCBM BHJ-PSC器件中的功能产生了强烈影响。
An amphiphilic surfactant oleamide was incorporated into P3HT:PCBM bulk heterojunction polymer solar cells (BHJ-PSCs) as a novel cathode buffer layer (CBL) for the first time by doping in the P3HT:PCBM photoactive layer followed by self-assembly. The power conversion efficiency (PCE) of the annealed P3HT:PCBM/oleamide BHJ-PSC device is enhanced by ∼28% at the optimum oleamide doping ratio of 2.5%, which is primarily due to the increase of fill factor (FF) by ∼22%. The surface morphologies of the oleamide-incorporated P3HT:PCBM photoactive films were studied by transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning Kelvin probe microscopy (SKPM), revealing that oleamide molecules initially doped in the P3HT:PCBM layer may undergo self-assembly and migrate to the top surface of the P3HT:PCBM layer, leading to the formation of a cathode buffer layer (CBL) as an interfacial dipole layer between the photoactive layer and Al cathode electrode. Such an oleamide interfacial dipole layer lowers the work function of Al, thus the energy level offset between the work function of Al and the LUMO level of the PCBM acceptor is decreased, facilitating the electron extraction by the Al cathode. Furthermore, we found that the crystallinity of P3HT upon the incorporation of oleamide was almost unchanged according to X-ray diffraction (XRD) characterization. It is noteworthy that, this phenomenon is completely different from the case of the previously reported analogous surfactant oleic acid, which was doped in the P3HT:PCBM photoactive layer and led to the efficiency enhancement as well due to the increased crystallinity of P3HT, suggesting the strong influence of the terminal group of the surfactant on its function in P3HT:PCBM BHJ-PSC devices.