Collaborative Research: Photoswitchable Interlayer Exciton Devices from 2D Hybrid Heterostructures

合作研究：2D混合异质结构的可光开关层间激子器件这笔赠款将支持普渡大学和圣托马斯大学之间的一个合作研究项目，该项目侧重于研究二维(2D)材料。原子薄的过渡金属二卤化物，如MoS_2和WSe_2，具有大块晶体所不具备的独特的物理性质。其中包括由于电子-空穴对的复合而产生的强烈光致发光，在量子力学术语中称为激子。将两种不同的二维材质(例如MoS2/WSe2)放在一起时，会出现一种新现象。这被称为层间激子，源于异质层之间的强相互作用。尽管层间激子在各种应用中的潜在影响令人兴奋，但相关的机制还没有完全被理解。这项研究引入了新的策略来调节层间激子的形成和行为，从而获得了一个基本的理解并开发了实用的器件。功能有机层将与2D异质结构相互作用，包括光敏分子，这些分子可以在外部光照射下改变光学和电子性质。该项目将结合先进的实验测量与建模和计算能力，以阐明2D材料与有机层之间的基本相互作用，以及相关的层间激子性质。这项研究还将得到一个教育和推广计划的补充，以促进公众对纳米科学和工程的理解。这些活动包括(I)开发新的课程材料，(Ii)为本科生提供基于研究的工程教育，以及(Iii)为K-12学生开发一个演示2D材料原理的动手模块。研究的中心目标是展示过渡金属二卤化物和光致变色分子的2D异质结构混合器件，并研究相关的光电性质。功能分子库将被检查，以便它们的最高占据分子轨道和最低未占据分子轨道能级将被诸如辐射波长之类的外部信号所切换。我们将利用光开关行为来调制异质双薄膜中的层间激子，并将研究几种不同的器件结构。我们将在普渡大学用光学光谱学和导电原子力显微镜来构建和研究杂化异质结构。圣托马斯大学将进行基于密度泛函理论的从头计算，以指导和验证实验。该项目团队将共同开发控制可光开关层间激子器件的关键参数的机械理解，并巩固结构与性能之间的关系，使之符合一般设计原则。这项工作的基础知识将为理解2D材料的体系结构和提供新的光电子器件奠定基础，从而产生革命性的影响。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。

Collaborative Research: Photoswitchable Interlayer Exciton Devices from 2D Hybrid HeterostructuresThis grant will support a collaborative research program between Purdue University and the University of St. Thomas, which focuses on investigating two dimensional (2D) materials. Atomically thin transition metal dichalcogenides such as MoS2 and WSe2 show unique physical properties which may not be observed from bulk crystals. These include strong photoluminescence due to the recombination of an electron-hole pair, called exciton in a quantum mechanical term. When two dissimilar 2D materials are brought together (for example, MoS2/WSe2), a new phenomenon emerges. This is called interlayer exciton originating from strong interactions between the heterolayers. While there is an excitement about the interlayer excitons given their potential impact in diverse applications, the relevant mechanisms are not fully understood. This research introduces novel strategies to modulate the formation and behavior of interlayer excitons, thereby gaining a fundamental understanding and developing practical devices. Functional organic layers will interface with 2D heterostructures, including photosensitive molecules that can change the optical and electronic properties upon external light irradiation. This project will combine advanced experimental measurements with modeling and computational capabilities to elucidate the fundamental interactions between 2D materials and organic layers, and related interlayer exciton properties. The research will also be complemented by an educational and outreach program to advance the public understanding of nanoscale science and engineering. The activities include (i) development of new course materials, (ii) research-based engineering education for undergraduate students, and (iii) development of a hands-on module for K-12 students that illustrates the principles of 2D materials.The central goal of the research is to demonstrate 2D heterostructured hybrid devices from transition metal dichalcogenides and photochromic molecules and study the related optoelectronic properties. A library of functional molecules will be examined such that their highest occupied molecular orbital and lowest unoccupied molecular orbital levels will be switched by external signals such as irradiating wavelengths. The photoswitchable behaviors will be exploited for modulating the interlayer excitons in heterobilayers and several distinct device configurations will be investigated. The hybrid heterostructures will be constructed and studied with optical spectroscopy and conductive atomic force microscopy at Purdue University. Ab initio calculations based on density functional theory will be performed at the University of St. Thomas to guide and verify the experiments. The project team will together develop a mechanistic understanding of the key parameters that govern the photoswitchable interlayer exciton devices and underpin the structure-property relationship towards general design principles. The fundamental knowledge from this work will lay the foundations for understanding architectured 2D materials and providing novel optoelectronic devices, thus resulting in transformative impacts.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.