CAREER: Optoelectronic Probes of Interlayer Electron-Hole Pair Multiplication in Atomic Layer Semiconductor Heterostructures

非技术说明：几乎所有家用和商用太阳能电池板都采用光伏器件。这些设备通过一个重要的微观过程来操作：单个光粒子（光子）被吸收以产生单个的电荷载流子对（电子空穴对）。电子-空穴对然后被分离和收集以产生功率。光伏器件的效率取决于一个简单的竞争：光能要么转化为废热，要么转化为有用的电能。超薄材料可能会在这场竞争中取得平衡，因为它可以同时限制热量的产生，同时增加电子功率。该项目探索超薄材料，以了解称为电子空穴对倍增的基本过程。在这个过程中，单个光子被转换成多个电子空穴对，从而大大提高了器件效率。了解这些过程，以及超越理论效率极限的改进设计，预计将对设计新的超高效光伏器件具有广泛的意义。本研究中的一个协同项目是通过引入数据科学方法在基础研究和应用科学中日益重要的作用，整合各级本科教育。该项目的一个关键方面是通过强化培训和发展，促进代表性不足群体的科学接触，以及提高对代表性不足群体在专业科学职业中的机会的认识。技术描述：首席研究员和他的研究小组正在研究一种新型的超薄半导体光电池，其可以通过单个光子表现出高效的层间电子-空穴对倍增。研究工作正在解决几个基本挑战：（1）由于电子-空穴对倍增而控制和增强光电流功率转换效率，（2）通过有效的电荷载流子倍增和收集减少电子和热能耗散，以及（3）直接测量倍增的层间电子-空穴对的动态。为了实现研究目标，该团队利用多功能光电方法和方法来发现新现象，以推进纳米纤维，时空光谱和凝聚态测量的现状。通过开发创新的纳米光电器件和利用超快光激发光谱，PI正在探索一种高效的光能收集机制，其中能量弛豫主要通过电子自由度发生。该项目的多学科研究有可能拓宽对量子限制材料和二维异质结构中电子空穴对行为的理解，并指导下一代光伏器件的新设计原则。

Non-Technical Description: Nearly all household and commercial solar energy panels employ photovoltaic devices. These devices operate through an important microscopic process: an individual particle of light (a photon) is absorbed to create an individual pair of charge carriers (an electron-hole pair). Electron-hole pairs are then separated and collected to generate power. The efficiency of a photovoltaic device is governed by a simple competition: light energy is either converted into waste heat or useful electronic power. Ultra-thin materials may tip the balance in this competition by simultaneously limiting heat generation, while increasing the electronic power. This project explores ultra-thin materials to understand a fundamental process known as electron-hole pair multiplication. In this process, an individual photon is converted into multiple electron-hole pairs, thus dramatically increasing the device efficiency. Understanding such processes, together with improved designs that push beyond the theoretical efficiency limits, is expected to have a broad significance with regard to designing new ultra-efficient photovoltaic devices. A synergistic project within this research is the integration of undergraduate education across all levels by introducing the growing importance of Data Science methods in fundamental research and applied science. A key aspect of this project focuses on facilitating scientific exposure to underrepresented groups through intensive training and development, as well as raising awareness of the opportunities for underrepresented groups in professional scientific careers.Technical Description: The principal investigator and his research team are investigating a novel class of ultra-thin semiconductor photocells, which may exhibit highly efficient interlayer electron-hole pair multiplication by a single photon. The research efforts are addressing several fundamental challenges: (1) control and enhancement of photocurrent power conversion efficiency due to electron-hole pair multiplication, (2) reduction of electronic and thermal energy dissipation through efficient charge carrier multiplication and collection, and (3) direct measurement of the dynamics of multiplied interlayer electron-hole pairs. To accomplish the research objectives, the team utilizes versatile optoelectronic methods and approaches to uncover new phenomena to advance the current state of nanofabrication, spatio-temporal spectroscopy and condensed matter measurements. By developing innovative nano-optoelectronic devices and utilizing ultrafast photoexcitation spectroscopies, the PI is exploring a highly efficient mechanism of light energy harvesting, in which energy relaxation occurs predominantly through the electronic degree of freedom. The multi-disciplinary research of this project has a potential to broaden the understanding of electron-hole pair behavior in quantum-confined materials and two-dimensional heterostructures, and to guide new design principles for next-generation photovoltaic devices.