New design strategies for tuning electrode properties by SAMs

化学锚定自组装单分子膜(SAM)在有机和分子电子学领域发挥着至关重要的作用。它们通常被用来改变界面的电学性质或作为纳米器件的活性元件。在这方面特别感兴趣的是结合到金属电极上的自组装膜，当它们在其尾部被极性单元取代时，改变了电荷载流子注入。在这种情况下的一个复杂情况是，由于偶极-偶极排斥，在这种层中形成SAM成为一个挑战。为了解决这个问题，我们将设计新型的自组装膜，通过分布偶极单元来减少偶极-偶极斥力，或者通过在形成自组装膜的分子之间诱导氢键来稳定层。为了实现后一种方法，我们将研究与染料分子相关的系统，如Indigo或Quinacrione。对于这样的分子，例如通过硫酸盐锚定结合到金属表面，我们预计会有新的性质，比如前所未有的功函数修改，以及由于层内化学和静电耦合而产生的特殊电子特性。为了实现计划中的研究的全部潜力，我们将结合六个研究小组的理想互补的专门知识：A.Terfort(Univ.他们将利用分布的偶极矩或形成染料的氢键网络来合成所需的分子。M.Zharnikov(大学Heidelberg)和他的团队将设计出在金属衬底上生长这种自组装膜的优化策略，表征它们的结构电子性质，并将与R.Resel(TU Graz)的团队一起研究有机半导体在修饰电极上的生长。E.Zojer(TU Graz)和他的同事将使用原子建模来确定指导合成努力的最有希望的分子结构，并解释实验观察。K.Zojer(TU Graz)和她的学生将建模，SAM修饰的电极有望如何将电荷载流子注入改变为有机薄膜晶体管，并特别关注不均匀性在薄膜电子性能中的作用。最后，本项目中设计的自组装膜将被B.Stadlober和她的团队(Joannum Research)应用到实际的器件结构中。所有上述研究工作都将紧密联系在一起，形成由几个层次的信息交流保证的紧密反馈循环。从这么多不同方法的紧密结合中，我们期待着对所研究系统的电子和结构性质的理解达到前所未有的水平。这有可能显著影响人们对自组装单分子膜的看法，并促进它们在实际有机电子设备中的使用。此外，多学科的方法和激励的研究环境将极大地拓宽所有相关科学家的科学视角，特别是学生。

Chemically anchored self-assembled monolayers (SAMs) play a crucial role in the area of organic and molecular electronics. They are usually used to modify the electronic properties of interfaces or to act as the active elements of nano-scale devices. Of particular interest in this context are SAMs bonded to metal-electrodes, which, when substituted with polar units at their tails, modify charge-carrier injection. A complication in that context is that due to the dipole-dipole repulsion, SAM-formation in such layers becomes a challenge. To overcome that problem, we will design novel types of SAMs, where the layers are stabilized either by reducing dipole-dipole repulsion via distributing the dipolar units or by inducing hydrogen-bonds between the SAM-forming molecules. To realize the latter approach, we will study systems related to dye molecules like indigo or quinacridone. For such molecules bonded to metal surfaces, e.g., via thiolate anchors, we expect novel properties like work-function modifications of unprecedented magnitude as well as peculiar electronic characteristics arising from the intra-layer chemical and electrostatic coupling. To realize the full potential of the planned research, we will combine the ideally complementary expertise of six research groups: A. Terfort (Univ. Frankfurt) and co-workers will synthesize the required molecules either with distributed dipole moments or the H-bond network forming dyes. M. Zharnikov (Univ. Heidelberg) and his group will devise optimized strategies for growing such SAMs on metal substrates, characterize their structural electronic properties, and together with the group of R. Resel (TU Graz) will study the growth of organic semiconductors on modified electrodes. E. Zojer (TU Graz) and his co-workers will use atomistic modeling to identify the most promising molecular structures guiding the synthetic efforts and to explain experimental observations. K. Zojer (TU Graz) and her students will model, how SAM-modified electrodes are expected to change the charge carrier injection into organic thin-film transistors paying special attention to the role of inhomogenieties in the films electronic properties. Finally, the SAMs designed in this project will be applied in actual device-structures by B. Stadlober and her group (Joanneum Research). All above mentioned research efforts will be intimately linked in close feedback-loops guaranteed by several levels of information exchange. From the tight integration of so many different approaches we expect an unprecedented level of understanding of the electronic and structural properties of the studied systems. This has the potential to significantly impact the way one thinks about self-assembled monolayers and to promote their use in actual organic electronic devices. Moreover, the multi-disciplinary approach and the stimulating research environment will hugely broaden the scientific perspectives of all involved scientists, in particular the students.