Collaborative Research: Thermoelectric transport and carrier dynamics in three-dimensional chalcogenide nanowire networks

非技术描述：环境中热量丰富，因此固态热能收集作为可穿戴电子设备和传感器的替代电源前景看好。然而，传统的块体半导体大多是重的和不灵活的，因此不容易适合这些应用。该项目探索基于纳米技术的新材料概念和新的材料合成技术，以创建轻便、灵活和可扩展的材料系统，以实现高效的热能收集。该项目的目标是了解基于纳米线网络的复合材料中基本的热和电传输过程，并促进对这些潜在物理过程如何影响热能到电能转换特性的了解。该项目积极促进对下一代科学家和工程师的教育和培训，特别是在跨学科领域，特别是来自代表性不足的群体，这些领域在技术上很重要，对国家的持续经济活力至关重要。作为研究活动的直接成果，开发了在线模拟工具，用于课程和更广泛的受众。技术描述：这个项目研究三维硫化物纳米线网络中的基本热电传输物理。各种热电硫化物纳米线是由溶液合成的，并均匀分散在聚二甲基硅氧烷等厚而灵活的基质中，形成稳定的三维纳米线网络。这些纳米线网络为所得到的复合材料中的电荷载流子提供了有效的热电传输路径。在这个项目中，我们广泛地研究了纳米线之间结处的载流子隧穿对宏观热电性能的影响。这些基质提供了稳定和均匀的纳米线分散，以及它们自身的优势，如重量轻、成本低、机械灵活性和溶液可加工性，使其适合于大规模柔性热电材料的开发。在本项目中，我们还使用表面结合的有机分子或颗粒共轭聚合物来修饰纳米线界面，以研究它们对输运性质的影响。系统地研究了纳米线合成过程中生长在纳米线两端的异质结构势垒粒子，以期通过载流子能量过滤和少数载流子阻挡效应进一步提高热电性能。通过该项目开发了包括结隧道效应的广义传输理论，以了解广泛传输机制的基本物理，并为进一步的材料进步提供见解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical description: Heat is abundant in the environment, and thus solid-state thermal energy harvesting holds great promises as an alternative power source for wearable electronics and sensors. However, conventional bulk semiconductors are mostly heavy and nonflexible, therefore not readily suitable for these applications. This project explores new material concepts and novel material synthesis techniques based on nanotechnology to create lightweight, flexible, and scalable material systems for efficient thermal energy harvesting. The objective of this project is to understand the fundamental thermal and electrical transport processes in nanowire network-based composites and advance the knowledge of how these underlying physical processes affect the thermal-to-electric energy conversion properties. The project actively promotes education and training of next-generation scientists and engineers, particularly from underrepresented groups, in the interdisciplinary fields that are technologically important and critical for sustained economic vitality of the nation. As direct outcomes of the research activities, online simulation tools are developed for use in courses, as well as for broader audiences.Technical description: This project investigates the fundamental thermoelectric transport physics in three-dimensional chalcogenide nanowire networks. Various thermoelectric chalcogenide nanowires are solution-synthesized and uniformly dispersed in thick flexible matrices such as polydimethylsiloxane to create stable three-dimensional nanowire networks. These nanowire networks provide efficient thermoelectric transport paths for charge carriers in the resulting composite. The impact of carrier tunneling at the junctions between nanowires on the macroscopic thermoelectric properties is extensively studied in this project. The matrices offer stable and uniform dispersion of nanowires, along with their own advantages such as lightweight, low cost, mechanical flexibility, and solution-processability, all in all, making the composites suitable for the development of large-scale flexible thermoelectric materials. In this project, nanowire interfaces are additionally modified with surface-bound organic molecules or particulate conjugated polymers to study their impacts on the transport properties. Heterostructure barrier particles grown at the two ends of the nanowires during the nanowire synthesis are systematically investigated for further enhancement of thermoelectric properties via carrier energy filtering and minority carrier blocking effects. A generalized transport theory including the junction tunneling effects is developed through the project to understand the underlying physics over a broad range of transport regimes, and provide insights for further material advancement.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.