CAREER: Photonic spectrum splitting with nanocrystal luminophores

太阳是地球上最丰富的可持续能源的潜在来源。 太阳能电池捕捉太阳？s射线并将这种能量转化为电能，可以通过光子学来改进，光子学使用先进的材料来引导光路通过设备。该项目将开发包含纳米晶体-聚合物复合材料的光子结构，该材料将太阳光谱分离并集中成其组成波长，然后将集中的特定波长引导到最能将这些波长能量转换为电能的半导体材料。通过这些过程的组合，可以提高太阳能转换的整体效率。 拟议的研究目标设计可以很容易地实现与现有的太阳能电池制造工艺，也可以集成到建筑物的建筑特征。这些光子材料还可以在医疗诊断、固态照明和显示技术的生物成像中找到其他应用。 该项目还具有广泛的教育目标，与研究活动相结合，旨在通过基于项目的太阳能学习，鼓励女性和代表性不足的少数民族进入STEM职业。该项目将解决太阳能光伏转换太阳光到电力的根本挑战-宽太阳光谱与仅有效转换带隙能量附近波长的光的半导体之间的不匹配。 在传统的多结太阳能电池中，光必须通过设计用于捕获一部分太阳光谱的半导体层的堆叠来传输。 光通过该堆叠的传递导致吸收损失，这降低了理论上可达到的太阳能转换效率。 将太阳光谱分成分量波长以及这些波长到相邻半导体的方向（与堆叠内相反）可以减少损耗并提高太阳能转换效率。 提出的研究的总体目标是开发一种有效的光谱分裂系统，用于提高太阳能收集使用光学材料，结合联合收割机光子结构与发光纳米晶体-聚合物复合材料。 为此，拟议的研究旨在从根本上了解这些纳米复合材料与各种光子结构的相互作用，以获取光。 研究计划有三个主要目标。第一个目标是考虑基于纳米复合发光聚光器的光子路径，以提高太阳光谱分裂的效率。 例如，通过将诸如布拉格反射镜的光捕获元件结合到发光集中器中，可以增加发光体量子产率。 第二个目标将通过调整发光纳米晶体-聚合物复合材料的性质来解决损耗机制。 例如，由交替的高折射率和低折射率纳米晶体-聚合物复合物组成的光子晶体可以减少发光集中器内的损耗。 在第三个目标中，光子纳米晶体-聚合物复合材料将被集成到单结太阳能光伏电池中，作为发光集中器，提供受控的发射角度，减少吸收损失，提高辐射衰减率。通过单结器件建立的设计原理将用于开发用于多结太阳能电池的光谱分离和集中系统，该系统使用设计有不同带隙的发光体来收集更大部分的太阳光谱。理论方法将把纳米级特性和光子结构与它们的性能联系起来，因为它们是接受漫射阳光并将其引导到相邻太阳能电池的波导。这些信息将用于预测单结和多结太阳能电池的效率上限。 实验工作将包括纳米材料-聚合物复合材料的合成，复合纳米结构与光学响应的相关性，以及光子结构的制造。 将使用光学光谱和电子显微镜来表征聚光器内的光传播。拟议的研究与教育活动相结合，这些活动侧重于在教育和推广平台上对太阳能进行基于项目的学习，包括开发介绍性讲座和实验室课程材料，为本科生妇女创建一个项目，以了解太阳能和相关可持续能源系统的本科生研究机会，和推广到K-12学生，强调工程在解决社会目标的作用。

The sun represents the most abundant potential source of sustainable energy on earth. Solar cells that capture the sun?s rays and convert this energy into electricity can potentially be improved through the science of photonics, which uses advanced materials to guide the light pathway through the device. This project will develop photonic structures which contain nanocrystal-polymer composite materials that split and concentrate the solar spectrum into its component wavelengths, and then direct the concentrated specific wavelengths to semiconductor materials that are best able to convert these wavelength energies into electricity. Through the combination of these processes, the overall efficiency for solar energy conversion can be increased. The proposed research targets designs that can be readily implemented with existing solar cell fabrication processes and could also be integrated into architectural features for buildings. These photonic materials may also find other applications in biological imaging for medical diagnostics, solid-state lighting, and display technology. This project also has broad educational goals coupled to the research activities, aimed at encouraging women and underrepresented minorities into STEM careers through project-based learning about solar energy.This project will address a fundamental challenge in solar photovoltaic conversion of sunlight to electricity - the mismatch between the broad solar spectrum and semiconductors that only efficiently convert light at wavelengths near their bandgap energy. In conventional multi-junction solar cells, the light must transfer through a stack of semiconductor layers designed to capture a portion of the solar spectrum. The transfer of light through this stack results in absorption losses that lower the theoretically-attainable solar energy conversion efficiency. The splitting of the solar spectrum into component wavelengths and the direction of these wavelengths to adjacent semiconductors, as opposed to within a stack, can reduce losses and improve solar energy conversion efficiency. The overall goal of the proposed research is to develop an efficient spectrum splitting system for enhancing solar energy harvesting using optical materials that combine photonic structures with luminescent nanocrystal-polymer composite materials. Towards this end, the proposed research seeks to gain a fundamental understanding of the interaction of these nanocomposite materials with various photonic structures for harvesting of light. The research plan has three primary objectives. The first objective is to consider photonic routes for enhancing the efficiency of solar spectrum splitting based on nanocomposite luminescent concentrators. For example, by incorporating light trapping elements such as Bragg mirrors into luminescent concentrators, luminophore quantum yield can be increased. The second objective will address loss mechanisms by tuning the properties of luminescent nanocrystal-polymer composite materials. For example, a photonic crystal consisting of alternating high index and low index nanocrystal-polymer composites could reduce losses within the luminescent concentrator. In the third objective, photonic nanocrystal-polymer composite materials will be integrated into single-junction solar photovoltaic cells to serve as luminescent concentrators that provide controlled angles of emission, reduced absorption loss, and enhanced radiative decay rate. The design principles established through the single-junction device will be used to develop a spectrum splitting and concentrating system for multi-junction solar cells that harvest a larger fraction of the solar spectrum using nanocrystal luminophores engineered with different bandgaps. Theoretical approaches will link nanoscale properties and photonic structures to their performance as waveguides that accept diffuse sunlight and direct it to adjacent solar cells. This information will used to predict the upper limits of efficiency for single and multi-junction solar cells. Experimental work will include synthesis of nanocrystal-polymer composites, correlation of the composite nanostructure to optical response, and fabrication of photonic structures. Optical spectroscopy and electron microscopy will be used to characterize the light propagation inside the concentrators. The proposed research is integrated with educational activities that focus on project-based learning about solar energy across educational and outreach platforms, including the development of introductory lecture and laboratory coursework materials, the creation of a program for undergraduate women to learn about undergraduate research opportunities in solar and related sustainable energy systems, and outreach to K-12 students that emphasizes the role of engineering in addressing societal goals.