Narrow Bandgap Multi-Stage Structures for Thermophotovoltaics

非技术描述：为世界机械提供动力所产生的能量中，约有三分之二以余热的形式损失。挽回这些巨大损失的哪怕是一小部分，都将对环境产生重大影响。该项目探索将废热转化为有用电能的半导体多层结构。该项目的目标是实现对多层半导体结构基本方面的广泛和系统的了解，并促进关于潜在物理过程如何影响其电学和光学性质的知识。这使得能够开发有效地将辐射能从热源转换为电能的新概念。该项目为俄克拉荷马大学的研究生和本科生提供了在材料科学、量子工程、光子学和器件制造等多学科主题上进行教育、培训和研究的独特机会。该项目还加强了俄克拉荷马州的科学和技术发展基础设施，并为来自代表性不足群体的学生提供了新的机会。技术说明：窄禁带材料是制造高效热光电(TPV)电池的理想材料，这种电池将热源中浪费的辐射能量转化为有用的电能。TPV器件利用InAs/GaSb接口的第二类带对齐形成多级级联结构。这些多级结构具有许多潜在的优点，包括：显著提高光生载流子的收集效率、广泛的红外光谱覆盖范围、级联结构导致的高开路电压，以及通过调整级联级数和单个吸收器层的厚度来实现电流匹配的好处。因此，这些窄禁带材料使TPV电池能够有效地吸收来自热源的红外辐射光子，并有效地将它们转化为电能。功率转换效率预计将接近20%，对于工作在长波长和来自低温光源的适度光强的TPV系统来说，这将是非常高的。该方法和任务涉及：多级TPV结构的理论发展和设计，TPV结构的分子束外延生长，材料表征，以及原型器件的制造和表征。由多级结构实现的TPV电池在废热回收、更有效地利用太阳能、太空探索、能量传输以及便携式和安静能源方面具有重要应用。这个项目不仅促进了对物理过程的理解，还在量子工程结构的设计中产生了新的知识，并扩大了它们的应用。中红外波段窄禁带多级TPV结构的发展是从广泛可用的热源中获取能量的关键一步。

Non-technical Description: About two-thirds of the energy generated to power the world's machinery is lost as waste heat. The recovery of even a fraction of these large losses would have a significant environmental impact. This project explores semiconductor multilayer structures for converting this otherwise wasted heat into useful electricity. The objectives of the project are to achieve extensive and systematic understanding of the fundamental aspects of the multilayer semiconductor structures, and to advance the knowledge of how underlying physical processes affect their electrical and optical properties. This enables development of novel concepts for effective conversion of radiant energy from a heat source into electricity. The project offers graduate and undergraduate students at the University of Oklahoma unique opportunities to pursue education, training and research in multidisciplinary topics, such as materials science, quantum engineering, photonics, and device fabrication. This project also enhances Oklahoma's infrastructure for science and technology development and opens new opportunities for students from under-represented groups. Technical Description: Narrow bandgap materials are desirable for making efficient thermophotovoltaic (TPV) cells that convert the otherwise-wasted radiant energy from a heat source into useful electrical energy. The TPV devices take advantage of the type-II band alignment of InAs/GaSb interfaces to form multi-stage cascade structures. These multi-stage structures have many potential advantages including: significantly improved collection efficiency for photo-generated carriers, a wide range of infrared spectral coverage, high open-circuit voltage due to the cascade architecture, as well as the benefits of current matching through adjustments of the number of cascade stages and the thickness of individual absorber layers. Consequently, these narrow bandgap materials enable TPV cells that effectively absorb infrared radiant photons from a heat source and efficiently convert them into electricity. The power conversion efficiency is expected to approach 20%, which would be remarkably high for a TPV system operating at long wavelengths and with a modest light intensity from a low temperature source. The approach and tasks involve: theory development and designs for multi-stage TPV structures, molecular beam epitaxial growth of the TPV structures, material characterization, and prototype device fabrication and characterization. The TPV cells enabled by multi-stage structures have important applications for waste-heat recovery, more efficient use of solar energy, space exploration, power beaming, as well as portable and quiet energy sources. This project not only advances the understanding of physical processes, it also generates new knowledge in the design of quantum-engineered structures and broadens their applications. The advancement of narrow bandgap multi-stage TPV structures in the mid-infrared wavelength region is a critical step toward harvesting energy from widely available heat sources.