Narrow Bandgap Multi-Stage Structures for Thermophotovoltaics

非技术性描述：世界上为机器提供动力所产生的能量中，约有三分之二以废热的形式损失。即使是恢复这些巨大损失的一小部分，也会对环境产生重大影响。该项目探索半导体多层结构，将这些浪费的热量转化为有用的电力。该项目的目标是实现对多层半导体结构的基本方面的广泛和系统的理解，并推进基本物理过程如何影响其电学和光学特性的知识。这使得能够开发用于将来自热源的辐射能有效地转换成电的新概念。该项目为俄克拉荷马州大学的研究生和本科生提供了独特的机会，可以在材料科学、量子工程、光子学和器件制造等多学科领域进行教育、培训和研究。该项目还加强了俄克拉荷马州的科学和技术发展的基础设施，并为代表性不足的群体的学生开辟了新的机会。技术说明：窄带隙材料对于制造高效的热光伏（TPV）电池是期望的，所述热光伏（TPV）电池将来自热源的否则浪费的辐射能转换成有用的电能。TPV器件利用InAs/GaSb界面的II型能带对准形成多级级联结构。这些多级结构具有许多潜在的优点，包括：显着提高收集效率的光生载流子，广泛的红外光谱覆盖范围，高开路电压，由于级联架构，以及通过调整级联级的数量和单个吸收层的厚度的电流匹配的好处。因此，这些窄带隙材料使得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其转化为电能。功率转换效率预计接近20%，这对于在长波长下操作并且具有来自低温源的适度光强度的TPV系统来说将是非常高的。该方法和任务涉及：理论发展和多级TPV结构的设计，分子束外延生长的TPV结构，材料表征，和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、电力集束以及便携式和安静的能源方面具有重要的应用。该项目不仅促进了对物理过程的理解，还产生了量子工程结构设计的新知识，并拓宽了其应用。中红外波段窄带隙多级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.