Polyoxometalate-Containing Linear-Dendritic Hybrids As Novel Optoelectronic Materials

技术总结这项提议的科学目标是开发一种新型的混合光伏材料，它结合了广泛的光捕获、高效和定向的能量转移、高效的光致电荷分离和双极电荷传输。具体地说，将设计一个线形-树枝状双嵌段体系，其中一端是基于三苯并五菲(TBP)的捕光共轭树枝状分子，另一端是含有多金属氧酸盐(POM)的线形聚合物。这两种不同的体系结构由一个双亚胺功能化的POM集群作为核心连接在一起。在分子水平上，共轭树枝有望捕获并单向地将光子能量输送到核心，在那里将通过配体到金属的电荷转移发生光致电子转移。在整体上，线状/树枝状体系的设计使得TBP环之间强烈的pi-pi堆积相互作用以及线状链段和树枝状链段之间的结构对比应该促进相分离，形成pi堆积的树枝状聚集型共轭结构域和富簇结构域。富团簇结构域传输电子，而pi共轭的树枝状结构域传输空穴。该项目的智力优势不仅在于开发了一种新型的基于多环芳烃结构块的捕光树枝状大分子(LHD)，以及第一个含有聚甲醛的线状-树枝状杂化材料，而且还在于对这些捕光材料的激子衰减途径、能量转移动力学、电子转移热力学和动力学的基本了解。此外，还可以深入了解纳米尺寸和带电的POM团簇如何影响线状-树枝状两嵌段共聚物的自组装。非技术性总结本项目旨在开发用于光伏(太阳能电池)应用的新型混合材料。这些材料包含聚合物和其他复杂的、高度支化的平面有机分子，它们将在特殊的分子结构中结合在一起。这将包括一个分子捕光组件和部分分子形成堆栈的能力，以指导电荷的运输。拟议活动的更广泛影响源于该项目的多学科性质、其潜在的技术进步及其与教育和外联的结合。展示和测试用于太阳能电池应用的新型杂化聚合物设计的技术影响直接关系到能源可持续性这一更广泛的挑战。该计划下的培训将为学生提供从化学合成到材料表征、器件制造和评估等多个领域的技能发展机会。该项目还将使私人投资机构能够继续扩大其对科学和技术领域代表性不足的学生的外联努力。

TECHNICAL SUMMARYThe scientific objective of this proposal is to develop a novel hybrid photovoltaic material which combines broad light-harvesting, efficient and directional energy transfer, efficient photoinduced charge separation, and bipolar charge transport. Specifically, a linear-dendritic diblock system will be designed where one end is a tribenzopentaphene (TBP)-based light-harvesting conjugated dendron while the other end is a polyoxometalate (POM)-containing linear polymer. These two different architectures are joined together by a diimido-functionalized POM cluster as the core. At the molecular level the conjugated dendrons are expected to harvest and funnel the photon energy unidirectionally to the core where photoinduced electron transfer will occur through the ligand-to-metal charge transfer transition. In bulk, the linear/dendritic system is so designed that the strong pi-pi stacking interaction among TBP rings and the architectural contrast between the linear block and the dendritic block should promote phase-separation to form pi-stacked dendron-aggregated conjugated domains and cluster-rich domains. The cluster-rich domain transports electrons while the pi-conjugated dendron domain transports holes. The proposed hybrids are thus potentially highly efficient PV materials with long-term stability.The intellectual merit of the project lies not only in the development of new materials including a new type of light-harvesting dendrimer (LHD) based on polycyclic aromatic hydrocarbon building blocks, and the first POM-containing linear-dendritic hybrids, but also in the fundamental understanding of exciton decay pathways, energy transfer dynamics, and electron transfer thermodynamics and kinetics of these light-harvesting materials. In addition, insight into how nanosized and charged POM clusters affect the linear-dendritic diblock copolymer self-assembly can be gained. NON-TECHNICAL SUMMARYThis project is aimed at developing new hybrid materials for photovoltaic (solar-cell) applications. These materials contain polymers and other complex, highly branched planar organic molecules that will be combined in special molecular architectures. These would include a molecular light-harvesting component and the ability of parts of the molecules to form stacks to direct the transport of electrical charges. The broader impact of the proposed activities stems from the project's multidisciplinary nature, its potential technological advances, and its integration with education and outreach. The technological impact of demonstrating and testing a novel hybrid polymer design for solar cell applications is directly related to the broader challenge of energy sustainability. The training under this program will offer students opportunities to develop skills in many areas from chemical synthesis to materials characterization and device fabrication and evaluation. The project will also allow the PIs to continue to expand their outreach efforts toward underrepresented students in science and technology.