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

Cronin/Esfarjani热离子传输因其提供用于废热回收的高效能量转换装置（例如，在汽车中）和在发电厂中联合发电。此外，高效的制冷系统可以提供与传统蒸汽压缩制冷系统相媲美的高效固态冷却。这些器件可用于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。除了热电能转换之外，所提出的电子输运研究将影响广泛的其他器件系统，包括发光二极管（LED）、场效应晶体管（FET）和谐振隧道二极管（RTD），目前正由其他研究小组进行研究。固态电子能量转换可以比基于体珀耳帖和塞贝克效应的常规热电能量转换更有效，如果超声波屏障能被合理设计的话然而，有相对较少的研究，固态电子能量转换，主要是因为难以制造接口与适当的能量障碍，表征热传输通过这些接口，并分离的体积热电性能的界面性能。二维层状异质结构使我们能够克服这些困难，并可能在热电发电机和冷却器的设计中创造一个高效率的范式转变。所提出的研究的目的是克服以前面临的挑战，使用分层异质结与栅极调谐的电子能垒高度的电子能量转换。除了优化和测量这些新型器件的热电优值（ZT）外，该项目还将：1。评估高度各向异性结构和弱界面货车德瓦尔斯结合是否引起低的跨平面热导率，2.）建立电子穿过货车德瓦耳斯键合界面的传输几乎没有散射的条件，3.）评估各种发射器和阻挡材料的性能（例如，BN、MoS2、Bi2Te3），4.）确定热电子引起热非平衡声子布居的程度，以及5.）单独的体效应和界面效应，以及6.）为了解决上述问题，开发了一个严格的模型，电子和声子输运通过这些新的设备使用第一原理的方法。

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.