Materials World Network: Interdisciplinary Bulk/Surface Studies of Transparent Conducting Oxides

这是西北大学（Thomas Mason）和达姆施塔特工业大学（Andreas Klein）的一个联合项目，旨在研究当前和新兴透明导电氧化物（tco）的体积与表面缺陷/电子结构。这种材料被用作先进的电光（E-O）设备的透明电极，如平板显示器、发光二极管和太阳能电池。然而，人们对它们的表面电子特性（例如，功函数）知之甚少，而这些特性在此类应用中与有源半导体材料的界面处建立潜在分布/频带偏移时起着重要作用。例如，铟锡氧化物或ITO，目前几乎所有E-O应用的主要TCO，在化学和电子方面与有机led和光伏中使用的p型有机物的HOMO水平不匹配。该研究的一个重要成果将是为ito替代tco收集急需的表面电子属性数据。目前，关于基型tco （CdO、ZnO、In2O3、SnO2）表面电子性质的研究文献有限，而对于更复杂的tco（二元、三元化合物及其固溶体）表面电子性质的研究几乎一无所知。这项跨学科的研究将西北大学的体合成和点缺陷研究与达姆施塔特工业大学的体和薄膜光电子能谱（XPS/UPS）相结合。通过了解体积和表面缺陷/电子结构之间的相关性，pi希望为技术上重要的E-O应用设计适当掺杂，具有良好特征和坚固的TCO电极表面。本研究由美国国家科学基金会国际科学与工程办公室西欧项目共同资助。

This is a joint project between Northwestern University (Thomas Mason) and the Technical University of Darmstadt (Andreas Klein) to investigate the bulk vs. surface defect/electronic structure of current and emerging transparent conducting oxides (TCOs). Such materials are employed as transparent electrodes in advanced electro-optic (E-O) devices such as flat-panel displays, light-emitting diodes, and solar cells. Yet little is known about their surface electronic properties (e.g., work functions), which play an important role in establishing potential distributions/band offsets at interfaces with the active semiconductor materials in such applications. For example, indium-tin oxide or ITO, the current workhorse TCO for virtually all E-O applications, is a poor match, chemically and electronically with the HOMO level of the p-type organics used in organic LEDs and photovoltaics. An important outcome of the research will be the collection of much-needed surface electronic property data for ITO-alternative TCOs. At present, there is only a limited literature for the surface electronic properties of the basis TCOs (CdO, ZnO, In2O3, SnO2) and almost nothing is known about the surface properties of the more complex TCOs (binary and ternary compounds and their solid solutions). This interdisciplinary effort combines bulk synthesis and point defect studies at Northwestern University with bulk and thin film photoelectron spectroscopy (XPS/UPS) at the Technical University of Darmstadt. By understanding the correlation between bulk and surface defect/electronic structure, the PIs hope to engineer appropriately doped, well-characterized, and robust TCO electrode surfaces for technologically important E-O applications. This work is co-funded by the Western Europe Program of the NSF Office of International Science and Engineering.