Collaborative Research: Thermionic Transport across Single and Multiple Barrier Heterostructures Based on 2D Layered Materials

CBET-1402906/1403089Cronin/EsfarjaniThermionic交通特别令人兴奋，因为它有潜力为发电厂的余热回收(例如，汽车)和热电联产提供高效的能量转换设备。此外，高效的热电子设备可以提供与传统蒸汽压缩制冷系统相媲美的高效固态制冷系统。这些设备可以用来为电子电路提供主动冷却，最终提高计算、传感和成像的性能。除了热电能量转换外，热离子输运的研究还将影响其他器件系统，包括发光二极管(LED)、场效应晶体管(FET)和共振隧道二极管(RTD)，目前其他研究小组正在进行研究。如果热离子势垒能够得到适当的设计，固态热电能量转换可以比传统的基于体Peltier和Seebeck效应的热电能量转换更有效。然而，关于固态热离子能量转换的研究相对较少，这主要是因为很难制备具有合适能量势垒的界面，表征这些界面上的热传输，以及将体相热电性质与界面性质分开。2D层状异质结使我们能够克服这些困难，并有可能为高效的热电发电机和冷却器的设计带来一种范式的转变。这项拟议的研究旨在克服以前面临的挑战，使用具有栅极调谐热离子势垒高度的分层异质结构来进行热离子能量转换。除了优化和测量这些新型器件的热电优值系数(ZT)外，该项目还将：1.评估高各向异性结构和弱界面van der Waals键合是否导致低的跨平面热导，2。建立在范德华键合界面上发生电子传输且几乎没有散射的条件，3.评估各种发射极和势垒材料(如BN、MoS2、Bi2Te3)的性能，确定热电子引起热非平衡声子布居的程度，以及5.)分离整体和界面效应，以及6.)为了解决上述问题，用第一性原理的方法建立了电子和声子在这些新型器件上传输的严格模型。

CBET-1402906/1403089Cronin/EsfarjaniThermionic transport is especially exciting for its potential to provide high-efficiency energy conversion devices for waste-heat recovery (e.g., in automobiles) and co-generation of electricity in power plants. In addition, highly efficient thermionics can provide efficient solid state cooling that rivals conventional vapor-compression refrigeration systems. These devices could be used to provide active cooling of electronic circuits, ultimately leading to increased performance of computing, sensing, and imaging. In addition to thermoelectric energy conversion, the proposed study of thermionic transport will impact a wide range of other device systems, including light emitting diodes (LEDs), field effect transistors (FETs), and resonant tunnel diodes (RTDs), currently being investigated by other research groups.Solid state thermionic energy conversion can be more efficient than conventional thermoelectric energy conversion based on bulk Peltier and Seebeck effects, if the thermionic barriers can be properly engineered. However, there have been relatively few studies on solid state thermionic energy conversion, mainly because of the difficulty of fabricating interfaces with the appropriate energy barriers, characterizing thermal transport across these interfaces, and separating the bulk thermoelectric properties from the interfacial properties. 2D Layered heterostructures enable us to overcome these difficulties, and can potentially create a paradigm shift in the design of thermoelectric power generators and coolers with high efficiency. The proposed study is designed to overcome the challenges previously facing thermionic energy conversion using layered heterostructures with gate-tuning of the thermionic barrier height. In addition to optimizing and measuring the thermoelectric figure of merit (ZT) of these novel devices, this project will: 1.) assess whether the highly anisotropic structure and the weak interface van der Waals bonding give rise to low cross-plane thermal conductance, 2.) establish the conditions under which electron transport across van der Waals bonded interfaces occurs with little scattering, 3.) evaluate the performance of various emitter and barrier materials (e.g., BN, MoS2, Bi2Te3), 4.) ascertain the extent to which hot electrons give rise to thermal non-equilibrium phonon-populations, and 5.) separate bulk and interfacial effects, and 6.) develop a rigorous model of the electron and phonon transport across these novel devices using a first-principles approach in order to address the above questions.