Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University , 200241 Shanghai, P.R. China.
Division of Surface Physics and Chemistry, IFM, Linköping University , SE-58183 Linköping, Sweden.
ACS Appl Mater Interfaces. 2018 Feb 21;10(7):6491-6497. doi: 10.1021/acsami.7b17368. Epub 2018 Feb 7.
The energy offset between the electrode Fermi level and organic semiconductor transport levels is a key parameter controlling the charge injection barrier and hence efficiency of organic electronic devices. Here, we systematically explore the effect of in situ oxygen exposure on energetics in n-type conjugated polymer P(NDI2OD-T2) films. The analysis reveals that an interfacial potential step is introduced for a series of P(NDI2OD-T2) electrode contacts, causing a nearly constant downshift of the vacuum level, while the ionization energies versus vacuum level remain constant. These findings are attributed to the establishment of a so-called double-dipole step via motion of charged molecules and will modify the charge injection barriers at electrode contact. We further demonstrate that the same behavior occurs when oxygen interacts with p-type polymer TQ1 films, indicating it is possible to be a universal effect for organic semiconductors.
电极费米能级和有机半导体输运能级之间的能量偏移是控制电荷注入势垒的关键参数，进而影响有机电子器件的效率。在这里，我们系统地研究了原位氧暴露对 n 型共轭聚合物 P(NDI2OD-T2) 薄膜中能态的影响。分析表明，一系列 P(NDI2OD-T2)电极接触中引入了界面位垒，导致真空能级的近恒定下位移，而真空能级与电离能之间保持恒定。这些发现归因于通过带电分子的运动建立了所谓的双偶极位垒，这将改变电极接触处的电荷注入势垒。我们进一步证明，当氧气与 p 型聚合物 TQ1 薄膜相互作用时，也会发生相同的行为，这表明它可能是有机半导体的一种普遍效应。
