Collaborative Research: Predictive theory, synthesis and characterization of a new type of transparent conductor without doping

非技术性说明：光伏太阳能电池、智能窗户、发光二极管、触摸屏传感器、电子纸和平板显示器等技术的运行需要一种关键组件，该组件既是电导体又是光学透明的，即所谓的透明导体。这些化合物是独特的，因为透明性和导电性通常是化合物的互斥特性。事实上，光学透明性（如窗玻璃）通常与电绝缘有关，而导电性（如铜或金）通常与光学不透明金属有关。已知的透明导体（诸如掺杂有Sn的氧化铟）通过在透明绝缘体中注入导电性来制成。该研究小组的目标是通过设计金属的透明度来开发一种新型的透明导体-金属陶瓷。这提出了一种新的方法来设计不同于电子性质的光学性质。该方法具有令人兴奋的智力影响，因为它提出了一种通用的逆向设计方法-从基于科学的设计原理开始，用作计算材料选择的“过滤器”，然后确定代表性的例子，然后进行实验室验证。CU Boulder和西北大学的研究生和博士后有令人兴奋的机会参与这项前沿研究工作。技术说明：透明导电氧化物是形成现代技术基础的矛盾材料，例如触摸屏、平板显示器、太阳能电池板等。当前用于发现新的透明导体的选择方法依赖于重掺杂透明绝缘体直到它们变成导电的。不幸的是，宽带隙材料本质上对电荷掺杂具有抵抗性，因为存在所谓的“掺杂缺陷”。即，将高浓度的自由载流子引入绝缘体中通常导致自发形成具有极性的结构缺陷，其补偿有意掺杂的极性。因此，寻找和优化这种技术关键的透明导电氧化物材料的进展令人沮丧地缓慢。研究小组提出了一个相反的，可能更有成效的替代方案，通过寻找符合一套具有特定能带结构的“设计原则”的化合物来设计金属的透明度。这种本征透明导体的设计规则是：（i）识别具有金属能带结构的化合物;使得（ii）其具有低等离子体频率和（iii）跨费米能级的低带间光吸收，以及（iv）将合成和表征应用于“最佳类”化合物，这里是Ba-Nb-O。金属透明导体最明显的优点是其导电性来自其高的固有载流子浓度。该提案中复杂的理论实验方法可以更有效地替代以前使用的试错法。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical description: Technologies such as photovoltaic solar cells, smart windows, light emitting diodes, touch-screen sensors, electronic papers, and flat panel displays require for their operation a critical component that is both an electrical conductor and optically transparent, the so-called transparent conductors. These compounds are unique, as transparency and conductivity are generally mutually exclusive properties of compounds. Indeed, optical transparency (as in window glass) is generally associated with electrical insulation, whereas electrical conductivity (such as in copper or gold) is generally associated with optically opaque metals. Known transparent conductors such as indium oxide doped with Sn are made by instilling conductivity in transparent insulators. The research team aims to develop a novel family of transparent conductors - metallic ceramics - by designing transparency in metals. This presents a new method to design optical properties as distinct from electronic properties. The approach has an exciting intellectual impact as it suggests a general approach for inverse design - starting from science-based design principles used as 'filters' for computational material selection, followed by identification of representative examples and then laboratory validation. The graduate students and postdocs of CU Boulder and Northwestern Universities are given exciting opportunities to participate in this cutting edge research effort. Technical description: Transparent conducting oxides are paradoxical materials that form the basis of modern day technologies, such as touch screens, flat panel displays, solar panels, etc. The current method of choice for discovering new transparent conductors have relied on heavily doping transparent insulators until they become conducting. Unfortunately, wide band gap materials are intrinsically resistant to doping of charges because of the existence of so-called 'doping bottlenecks'. Namely, the introduction of a high concentration of free carriers into insulators generally leads to the spontaneous formation of structural defects with polarity that compensate that of the intentional doping. Consequently, the progress in finding and optimizing such technologically critical transparent conducting oxide materials has been frustratingly slow. The research team proposes an opposite, and likely more fruitful alternative of designing transparency in metals by looking for compounds that obey a set of 'design principles' with specific band structures. The design rules for such intrinsic transparent conductors are: (i) identify a compound with metallic band structure; such that (ii) it has low plasma frequency and (iii) low inter-band optical absorption across the Fermi level, and (iv) apply synthesis and characterization to the 'best of class' compounds, here Ba-Nb-O. The most visible advantage of metallic transparent conductors is that their conductivity comes from their high, indigenous carrier concentration. The complex theory-experimental approach in the proposal enables more efficient progress as alternative to the previously used trial-and-error method.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.