Nanoscale Excitonics: From Materials Chemistry to Ultrafast Photonics

改变我们生活的电子设备都消耗能源。这些设备对我们产生维持运行所需的电力的能力提出了很高的要求。因此，找到创造新能源或提高能源效率的解决方案至关重要。在供应方面，由纳米科学实现的下一代光电子学就是纳米材料可以产生影响的一个例子。基于量子点（QD）的太阳能电池是从该领域出现的一种这样的技术。量子点光子学的基础科学是建立在这些材料生长的基础科学和对它们的功能如何从其结构产生的光谱理解之上的。在需求方面，现有室内光源的低效率正在导致新出现的能源危机。使用纳米材料的固态照明一直处于激烈的研究中，特别是出于这些原因-能源效率，可靠性和设备寿命。固态照明的最有前途的方法之一是使用半导体量子点的发光二极管。但是，无论是光化学、LED还是激光，仍然存在重大障碍。我们将这一需要和这一挑战视为机遇。** 半导体量子点（QD）一直在深入研究，以探索纳米材料中量子效应的基础科学，以及它们对太阳能电池，激光，生物成像和量子信息处理等各种应用的重要性。基于可以制造的丰富的纳米结构套件，现在已经有了一个强大的平台，用于开发各种新型设备，这些设备将对照明，显示器，电信和我们的能源未来产生影响。材料科学与器件应用的联系方式是这些系统的激子-激子的结构和动力学。我的团队使用各种方法探索半导体量子点的激子，最著名的是飞秒激光光谱学。** 在这里，我描述了我的团队正在着手探索和利用纳米结构中的激子的三个当前项目，以便深入了解它们的功能并在各种设备应用中实现它们的价值。这些项目都统一在一个共同的主题激子在纳米材料：从材料到设备，以先进的光谱。在本提案中，我们将完成以下工作：1）我们将使用我们在早期NSERC发现周期中开发的激子状态分辨泵浦/探测光谱来探索半导体纳米晶体的激子。2)我们将建立胶体量子点表面的第一个清晰的显微镜视图。基于这种理解，我们将利用量子点表面的化学功能化来设计波函数，用于包括节能白色光发射以及传感在内的应用。3)我们将开发一个简单而强大的方法，使用一种新的双脉冲整形器计划相干多维光谱。这个光谱学开发项目将导致一个独特的强大的方法来探索纳米系统中激子的结构和动力学。它还将为这项技术的商业化创造机会。

The electronic devices that have transformed our lives all consume energy. These devices are placing great demands upon our ability to generate the electrical power needed to maintain operation. Hence it is crucial to find solutions which either create new sources of energy or create greater energy efficiency. On the supply side, next generation photovoltaics enabled by nanoscience are one such example of the impact nanoscale materials can have. Quantum dot (QD) based solar cells are one such technology that has emerged from this field. The basic science of QD photovoltaics is built upon the basic science of the growth of these materials and the spectroscopic understanding of how their function arises from theis structure. On the demand sude, the poor efficiency of existing room light sources is now contributing to an emerging energy crisis. Solid state lighting using nanomaterials has been under intense investigation specifically for these reasons - energy efficiency, reliability, and device longevity. One of the most promising approaches to solid state lighting uses light emitting diodes using semiconductor quantum dots. But significant barriers remain, whether for photovoltaics, LEDs, lasers. We view this need and this challenge as an opportunity. **Semiconductor quantum dots (QD) have been under intense investigation in order to explore the basic science of quantum effects in nanoscale materials, as well as for their importance to a wide variety of applications such as solar cells, lasers, biological imaging and quantum information processing. Based upon the rich suite of nanostructures that may be fabricated, a powerful platform is now in hand for the development of a variety of novel devices that will have impact on lighting, displays, telecommunications, and our energy future. The way in which the materials science is connected to the device applications is the excitonics of these systems - the structure and dynamics of their excitons. My group explores the excitonics of semiconductor quantum dots using a variety of approaches, most notably femtosecond laser spectroscopy. **Here, I describe three current projects my group is embarking upon to explore and exploit excitons in nanostructures in order to produce insight into their function and to realize their value in a variety of device applications. These projects are unified under a common theme of excitonics in nanoscale materials: from materials to devices to advanced spectroscopy. In this proposal we will accomplish the following: 1) We will explore the excitonics of semiconductor nanocrystals using our excitonic state-resolved pump/probe spectroscopy developed in our earlier NSERC Discovery cycles. 2) We will establish the first clear microscopic view of the surface of colloidal quantum dots. Based upon this understanding, we will utilize chemical functionalization of the surface of quantum dots to engineer the wavefunctions for applications including energy efficient white light emission as well as sensing. 3) We will develop a simple and powerful approach to coherent multidimensional spectroscopy using a novel dual pulse shaper scheme. This spectroscopy development project will result in a uniquely powerful approach to exploring the structure and dynamics of excitons in nanosystems. It will moreover enable opportunities for commercialization of this technology.