Nanoscale Excitonics: From Materials Chemistry to Ultrafast Photonics

改变我们生活的电子设备都要消耗能源。这些设备对我们产生维持运行所需电力的能力提出了很高的要求。因此，找到既能创造新能源又能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伏发电就是纳米材料影响的一个例子。基于量子点（QD）的太阳能电池就是从这一领域出现的一种这样的技术。量子点光伏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结构中产生的光谱理解之上的。在需求方面，现有房间光源的低效率正在造成新的能源危机。由于能效、可靠性和器件寿命等原因，使用纳米材料的固态照明一直受到密切的研究。最有前途的固态照明方法之一是使用半导体量子点的发光二极管。但是重大的障碍仍然存在，无论是光伏、led还是激光。我们将这一需求和挑战视为机遇。

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.