CAREER: Realizing next generation light-material interactions via directional, collective photoluminescence and energy transport of surface-sensitive nanocrystals

电子设备无处不在，对能源的需求日益增长。通过可再生能源发电和减少能源消耗，节能设备将在解决这些需求方面发挥重要作用。能源效率的一个例子来自于广泛用于显示器和照明的发光二极管（led）。向前发射的光脱离设备而被看到。以广角发射的光可能会被困在设备内部并被浪费掉。因此，控制发光方向可以提高LED的效率。这个职业项目的重点是了解纳米级材料的基本电子和光子过程，这些材料可以表现出高度定向的光发射。这项工作的发现可以实现超高效率的照明、显示器和太阳能电池。它们还将为光学计算和数据存储等新技术提供基础。研究者还将通过培训女性和未被充分代表的少数民族成为STEM领域的领导者，来解决可持续发展方面的技术和社会挑战。计划的活动包括案例研究项目、本科生研究机会和以太阳能产业为重点的技术学院。本CAREER项目的目标是了解铯卤化铅纳米晶体的光物理学，铯卤化铅纳米晶体是一种高性能纳米材料，具有非凡的光学特性，如超荧光、单光子发射、能量和自旋漏斗。三个研究目标是通过研究角寿命来将这些纳米晶体的可调谐定向光致发光与超荧光联系起来；确定这些材料中激子和自旋方向的极限；并量化了表面电荷和外加电压对单个纳米晶体激子输运和光发射路径的影响。研究团队将利用一系列光学表征技术，量化光和能量传输如何依赖于单个纳米晶体和超晶格的大小、形状、组成和局部环境。由于非凡的光学特性表现出强烈的角度依赖性，研究小组将使用时间分辨后焦平面成像来量化光发射和能量传递的时间特性，作为角度和动量的函数。这项工作涉及材料合成的化学方法、表面化学和决定光在材料中传播的光子设计原理的交叉，创造了一个理解纳米尺度光-物质相互作用所必需的视角。这项工作将为其他纳米材料系统提供启示，并有可能使新的量子信息技术和光电子技术的效率接近热力学极限。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical DescriptionElectronic devices are everywhere, and drive increasing demands for energy. Energy-efficient devices will play an important role in addressing these needs through renewable energy generation and reduced energy consumption. One example of energy efficiency comes from light-emitting diodes (LEDs), widely used for displays and lighting. Light emitted in the forward direction escapes the device and is seen. Light emitted at a wide angle can be trapped inside the device and is wasted. Thus, controlling the direction of light emission can increase the efficiency of an LED. This CAREER project focuses on understanding the fundamental electronic and photonic processes of nanoscale materials that can exhibit highly directional light emission. Discoveries in this work could enable ultra-high efficiency lighting, displays, and solar cells. They also will provide the foundation for novel technologies such as optical computing and data storage. The investigator will also address the technological and social challenges in sustainability by training women and underrepresented minorities to be leaders in STEM. Planned activities include case study projects, undergraduate research opportunities, and a solar industry-focused Technical Academy. Technical DescriptionThe goal of this CAREER project is to understand the photophysics of cesium lead halide nanocrystals, a high-performance nanomaterial with extraordinary optical properties such as superfluorescence, single photon emission, and energy and spin funneling. The three research objectives are to correlate the tunable, directional photoluminescence to superfluorescence of these nanocrystals by studying angular lifetime; determine the limit of exciton and spin directionality in these materials; and quantify the effect of surface charge and applied voltage to the exciton transport and light emission pathways of individual nanocrystals. The research team will quantify how light and energy transport depends on the size, shape, composition, and local environment of individual nanocrystals and superlattices using an array of optical characterization techniques. Because extraordinary optical properties exhibit strong angle dependence, the research team will use time-resolved back focal plane imaging to quantify the temporal properties of light emission and energy transfer as a function of angle and momentum. The work operates at the intersection of chemical approaches to materials synthesis and surface chemistry and photonic design principles that dictate light propagation in materials, creating a perspective that will be necessary to understanding nanoscale light-matter interactions. This work will shed light on other nanomaterial systems and has the potential to enable novel quantum information technologies and optoelectronic technologies with efficiencies approaching thermodynamic limits.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.