CAREER: Defects and Polarons in Complex Materials

该职业奖支持用于能源、电子和光电子应用的复杂材料缺陷计算建模的研究和教育。缺陷在改变许多材料的性能方面起着至关重要的作用，其中一些与我们的日常生活具有很高的技术相关性。例如，硅和砷化镓等半导体的导电性可以通过添加微小浓度的杂质来急剧改变，从而实现各种微电子器件（如无处不在的晶体管），这些器件存在于我们当前的计算机、智能手机和平板电脑内的微芯片中。另一方面，缺陷可能对设备性能有害，就像限制太阳能电池效率的缺陷一样。我们控制缺陷类型和数量的能力决定了给定材料是否适合器件应用。因此，理解和控制缺陷对于电子和光电子新材料的发展至关重要。利用电子结构理论和超级计算机的先进方法，PI将研究一系列复杂材料中缺陷的作用，这些材料表现出一系列令人兴奋的物理特性。这项研究可能会增强现有的性能，并可能导致发现可以用于新型设备设计的新性能。此外，该项目将具有显著的教育价值，包括研究生和K-12高中学生的培训。研究生将学习前沿的计算方法和材料理论的先进概念；他们还将参加一个拓展项目，包括向高中生教授科学编程，吸引他们从事科学技术事业。通过暑期实习，高中生将开发数据处理工具，帮助研究生处理复杂的数据可视化。这些工具将通过PI的研究网站免费提供。该职业奖支持对用于能源、电子和光电子应用的复杂材料的缺陷和电荷定位的计算建模的研究和教育。大多数材料的性能都受到缺陷的强烈影响。例如，在半导体中加入微量的杂质，就能大幅度改变其导电性，使良好的绝缘体变成优良的导体。缺陷也可能对器件性能有害，如在太阳能电池的情况下，缺陷会导致不必要的非辐射载流子重组，并强烈影响效率。基于密度泛函理论的计算机建模已经成为研究各种材料缺陷的有力工具，它提供了关于浓度、电学和光活性的信息。这些计算通常通过提供在原子尺度上难以探测的重要性质和现象来补充实验。在这个项目中，PI将使用最先进的计算方法来研究由部分填充d或f壳层的元素制成的氧化物中缺陷的作用。感兴趣的材料包括钙钛矿、层状钙钛矿和焦绿石。这些材料有潜力实现新的设备和功能，因为它们最有趣的特性受到杂质和缺陷的强烈影响。该项目将促进对缺陷和杂质对这些复杂材料的电子和光学性质的影响的基本理解。在实现器件应用的关键步骤中，该项目将提供有关平衡缺陷浓度，电学和光学活动以及缺陷与载流子和迁移之间关系的信息。最终，它将用于识别对器件中材料性能有害的缺陷，并将通过掺杂或合金化为设计缺陷提供基础，以增强或扩大材料的功能。此外，该项目将具有显著的教育价值，包括研究生和K-12高中学生的培训。研究生将学习前沿的计算方法和材料理论的先进概念；他们还将参加一个拓展项目，包括向高中生教授科学编程，吸引他们从事科学技术事业。通过暑期实习，高中生将开发数据处理工具，帮助研究生处理复杂的数据可视化。这些工具将通过PI的研究网站免费提供。

NONTECHNICAL SUMMARYThis CAREER award supports research and education on the computational modelling of defects in complex materials that are used for energy, electronics, and optoelectronics applications. Defects play a crucial role in altering the properties of many materials, some of which are of high technological relevance and central to our daily life. For example, the electrical conductivity of semiconductors such as silicon and gallium arsenide can be drastically modified by adding minute concentrations of impurities, enabling a variety of microelectronic devices (such as the ubiquitous transistor) that are present in the microchips inside our current computers, smart phones, and tablets. On the other hand, defects can be detrimental to device performance, as is the case for defects that limit the efficiency of solar cells. Our ability to control the type and amount of defects present determines if a given material will be suitable for device applications. Understanding and controlling defects is therefore crucial to the development of novel materials for electronics and optoelectronics. Using advanced methods of electronic structure theory and supercomputers, the PI will investigate the role of defects in a series of complex materials that exhibit an array of exciting physical properties. The research may enhance the existing properties, and could lead to the discovery of new ones that can be used in novel device designs.In addition, this project will have significant educational value, incorporating training of graduate and K-12 high-school students. The graduate students will learn cutting-edge computational methods and advanced concepts in materials theory; they will also participate in an outreach program that involves teaching scientific programing to high-school students, enticing them to a career in science and technology. Through summer internships, high-school students will work on developing data-manipulation tools that will help the graduate students with complex data visualization. The tools will be freely available through the PI's research website.TECHNICAL SUMMARYThis CAREER award supports research and education on the computational modelling of defects and charge localization in complex materials that are used for energy, electronics, and optoelectronics applications. The properties of most materials are strongly affected by the presence of defects. For example, adding minute concentrations of impurities to a semiconductor can drastically change its electrical conductivity by several orders of magnitude, transforming a good insulator into an excellent conductor. Defects can also be detrimental to device performance, as in the case of solar cells, where defects cause unwanted nonradiative carrier recombination, and strongly impact efficiency. Computer modelling based on density functional theory has turned into a powerful tool in the study of defects in various types of materials, providing information on concentrations, and on electrical and optical activities. These calculations often complement experiments by giving access to important properties and phenomena that are difficult to probe at the atomic scale. In this project the PI will use state-of-the-art computational methods to investigate the role of defects in oxides made of elements with partially filled d or f shells. The materials of interest include perovskites, layered perovskites, and pyrochlores. These materials have potential to enable novel devices and functionalities, as their most interesting properties are strongly influenced by the presence of impurities and defects. This project will advance fundamental understanding of the impact of defects and impurities on the electronic and optical properties of these complex materials. In a crucial step towards enabling device applications, the project will provide information on equilibrium defect concentrations, electrical and optical activities, and the relation between defects and charge carriers and migration. Ultimately, it will serve to identify defects that are detrimental to materials performance in devices, and will provide a basis to engineer defects, through doping or alloying, to enhance or broaden materials functionality.In addition, this project will have significant educational value, incorporating training of graduate and K-12 high-school students. The graduate students will learn cutting-edge computational methods and advanced concepts in materials theory; they will also participate in an outreach program that involves teaching scientific programing to high-school students, enticing them to a career in science and technology. Through summer internships, high-school students will work on developing data-manipulation tools that will help the graduate students with complex data visualization. The tools will be freely available through the PI's research website.