Kirchhuebel Tino, Gruenewald Marco, Sojka Falko, Kera Satoshi, Bussolotti Fabio, Ueba Takahiro, Ueno Nobuo, Rouillé Gaël, Forker Roman, Fritz Torsten
Institute of Solid State Physics, Friedrich Schiller University Jena , Helmholtzweg 5, 07743 Jena, Germany.
Institute for Molecular Science , Myodaiji, Okazaki 444-8585, Japan.
Langmuir. 2016 Mar 1;32(8):1981-7. doi: 10.1021/acs.langmuir.5b04069. Epub 2016 Feb 19.
Tetraphenyldibenzoperiflanthene (DBP) is a promising candidate as a component of highly efficient organic photovoltaic cells and organic light-emitting diodes. The structural properties of thin films of this particular lander-type molecule on Ag(111) were investigated by complementary techniques. Highly ordered structures were obtained, and their mutual alignment was characterized by means of low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) images reveal two slightly different arrangements within the first monolayer (ML), both describable as specific herringbone patterns with two molecules per unit cell whose dibenzoperiflanthene framework is parallel to the surface. In contrast, single DBP molecules in the second ML were imaged with much higher intramolecular resolution, resembling the shape of the frontier orbitals in the gas phase as calculated by means of density functional theory (DFT). Further deposition leads to the growth of highly ordered bilayer islands on top of the first ML with identical unit cell dimensions and orientation but slightly inclined molecules. This suggests that the first ML acts as a template for the epitaxial growth of further layers. Simultaneously, a significant number of second-layer molecules mainly located at step edges or scattered over narrow terraces do not form highly ordered aggregates.
四苯基二苯并苝（DBP）作为高效有机光伏电池和有机发光二极管的组成部分是一个很有前景的候选材料。通过互补技术研究了这种特殊的着陆器型分子在Ag(111)上的薄膜结构特性。获得了高度有序的结构，并通过低能电子衍射（LEED）对它们的相互排列进行了表征。扫描隧道显微镜（STM）图像显示在第一单层（ML）内有两种略有不同的排列，两者都可描述为特定的人字形图案，每个晶胞中有两个分子，其二苯并苝骨架与表面平行。相比之下，第二个ML中的单个DBP分子以更高的分子内分辨率成像，类似于通过密度泛函理论（DFT）计算的气相前沿轨道的形状。进一步沉积导致在第一个ML顶部生长出高度有序的双层岛，其晶胞尺寸和取向相同，但分子略有倾斜。这表明第一个ML作为后续层外延生长的模板。同时，大量主要位于台阶边缘或散布在狭窄台面上的第二层分子不会形成高度有序的聚集体。
