A Route Towards Efficient Energy Relaxation from Nanocrystals to Oxide-free Semiconductor Surfaces

摘要技术：基于能量转移的混合纳米结构由具有单独功能的组件明智地设计，为光电器件应用提供了多功能平台。在混合物的强吸收组分中的光吸收之后是从纳米结构中所得的激子到导电半导体薄膜中的电子-空穴对的非接触式电磁能量转移。 这种在具有良好控制界面的纳米材料中对激发的电磁操纵是迈向下一代功能纳米器件的重要一步，该功能纳米器件不依赖于组件之间的电荷转移。该项目的重点是辐射和非辐射的能量转移现象之间的基本原理，高吸收的量子点（NQD）和高迁移率的硅半导体组件结合在层状混合纳米结构。第一项工作的目的是研究非辐射能量转移从单分子膜的NQD共价接枝在Si表面。为了促进完全的光吸收，多层NQD结构将被制造和能量“漏斗”扩散通过非辐射相互作用到Si衬底之间的nQD层进行探索和优化。第二个任务的重点是在硅纳米膜中的微波辐射耦合到波导模式。放置在高介电常数材料（例如Si）附近时，在Si层中，电子发射被转换为波导模式，在Si层中，电子发射最终被吸收，从而有助于整体能量转移。第三个方向探讨了新的多壳层NQD的适用性，具有长寿命的多激子态的能量转移。采用时间分辨光致发光光谱结合光电流测量的平面NQD/Si结构的整体能量转移效率进行评估。这项研究的结果将导致混合激子结构中的能量转移途径的理解，克服与界面态相关的电荷捕获。结合建模工具和实现所需功能的指导方针，这些结果可以应用于设计高效光伏结构的实用架构。非技术性：纳米结构由附着在薄硅膜上的纳米颗粒组成，为现代光子学提供了一个多功能平台，可应用于先进传感、光电子学和新型发光源。该项目的基础研究成果预计将显著影响我们对这些纳米结构中的能量转移现象和操纵的理解，从而产生更有效的光电器件，对社会大有裨益。参加这项研究的学生能够获得激子和混合纳米材料领域的专业知识。该研究本质上是跨学科的，使学生能够熟练掌握物理学，光子学和材料科学，并发展实验和建模技能。一个强大的努力，致力于参与本科和大学预科学生，促进他们对科学的兴趣。该项目的PI致力于通过开发可持续能源光子学应用课程以及与当地行业的互动来加强课程的知识转移。

Abstract Technical: Energy-transfer-based hybrid nanostructures judiciously engineered from components with separate functionalities offer a versatile platform for optoelectronic device applications. Light absorption in the strongly absorbing component of the hybrid is followed by non-contact electromagnetic energy transfer from the resulting excitons in nanostructures to electron-hole pairs in the conductive semiconductor thin film. This electromagnetic manipulation of excitations in nanoscale materials with well-controlled interfaces is an important step towards the next generation of functional nanodevices, which does not rely on charge transfer between the components. This project focuses on the fundamental principles of radiative and non-radiative energy transfer phenomena between highly absorbing nanocrystal quantum dots (NQDs) and high-mobility Si semiconductor components combined in layered hybrid nanostructures. The first effort aims to study non-radiative energy transfer from monolayers of NQDs covalently grafted on Si surfaces. To facilitate complete light absorption, multilayer NQD structures are to be fabricated and energy 'funneling' diffusion via non-radiative interactions between nanocrystal layers into Si substrate is explored and optimized. The second task focuses on radiative coupling of nanocrystal emission to waveguiding modes in Si nanomembranes. Placed in the vicinity of a high dielectric constant material such as Si, the nanocrystal emission is converted to waveguide modes in the Si layer where it is eventually absorbed, contributing to overall energy transfer. The third direction explores the applicability of new multishell NQDs that possess long-lived multiexitonic states for energy transfer. The overall energy transfer efficiency of planar NQD/Si structures is assessed by employing time-resolved photoluminescence spectroscopy combined with photocurrent measurements. The results of this research will lead to the understanding of energy transfer pathways in hybrid excitonic structures that overcome charge trapping related to interfacial states. Together with modeling tools and guidelines for achieving desired functionalities, these results could be applied to engineer practical architectures for efficient photovoltaic structures.Non-technical: Nanostructures composed on nanoparticles attached to thin silicon films offer a versatile platform for modern photonics with applications in advanced sensing, photovoltaics and novel light emitting sources. The fundamental research results of this project are expected to significantly impact our understanding of energy transfer phenomena and manipulation in these nanostructures leading to more efficient optoelectronic devices of great benefit to society. Students participating in this research are able to acquire expertise in the field of excitonics and hybrid nanomaterials. The research is inherently interdisciplinary in nature, allowing students to gain proficiency in physics, photonics and materials science and to develop both experimental and modeling skills. A strong effort is devoted to involve undergraduate and pre-college students and facilitate their interest in science. The PI of this project is committed to knowledge transfer via enhancing the curriculum by developing a course on Photonics Applications for Sustainable Energy and the interaction with the local industry.