Palmgren P, Yu S, Hennies F, Nilson K, Akermark B, Göthelid M
Materials Physics, MAP, ICT, Royal Institute of Technology, Electrum 229, SE-16440 Stockholm, Sweden.
J Chem Phys. 2008 Aug 21;129(7):074707. doi: 10.1063/1.2969081.
Surface modification of reactive oxide substrates to obtain a less strongly interacting template for dye adsorption may be a way to enhance performance in dye-sensitized solar cells. In this work, we have investigated the electronic and structural properties of 4,4(')-bipyridine (bipy) as modifier adsorbed on the TiO(2)(110) surface. The modified surface is then coated with iron phthalocyanine (FePc) and the properties of this heterostructure are investigated with synchrotron based photoelectron spectroscopy, x-ray absorption spectroscopy, and scanning tunneling microscopy. We find that a saturated monolayer consisting of standing bipy molecules with one nitrogen atom pointing outward is formed on the oxide surface. FePc adsorb in molecular chains along the [001] direction on top of bipy and ordered in a tilted arrangement with adjacent molecules partially overlapping. Already from the first layer, the electronic properties of FePc resemble those of multilayer films. FePc alone is oxidized on the TiO(2)(110) surface, but preadsorbed bipy prevents this reaction. The energy level lineup at the interface is clarified.
对活性氧化物基底进行表面改性以获得用于染料吸附的相互作用较弱的模板，可能是提高染料敏化太阳能电池性能的一种方法。在这项工作中，我们研究了作为改性剂的4,4'-联吡啶（bipy）吸附在TiO₂(110)表面的电子和结构性质。然后在改性表面上涂覆铁酞菁（FePc），并用基于同步加速器的光电子能谱、X射线吸收光谱和扫描隧道显微镜研究这种异质结构的性质。我们发现，在氧化物表面形成了由直立的bipy分子组成的饱和单层，其中一个氮原子向外。FePc沿着[001]方向在bipy顶部以分子链形式吸附，并以倾斜排列有序排列，相邻分子部分重叠。从第一层开始，FePc的电子性质就类似于多层膜的电子性质。单独的FePc在TiO₂(110)表面被氧化，但预先吸附的bipy可防止这种反应。界面处的能级排列得以阐明。
