Probing and optimizing quantum dot confined states for next generation intermediate band solar cells

技术优点：中波段（IB）太阳能电池具有以创纪录的效率将太阳光转化为电能的潜力。也许最有前途的IB半导体方法是量子点（QD）阵列。原则上，这些量子点阵列将取代最先进的p-i-n太阳能电池的固有区域。虽然这个概念最初是在20世纪90年代提出的，但预期的效率记录尚未实现。迄今为止，由于缺乏在量子点受限态和微带环境下能量转换过程的基本设计规则，性能受到限制。特别是，需要了解量子点形状、尺寸、应变状态和量子点/矩阵界面均匀性对量子点受限态和微带形成和相互作用的影响。此外，必须开发能够实现最佳光电转换效率的新型小频段架构。所提出的方法包括最先进的纳米制造方法、前所未有的空间分辨率测量和多尺度模拟的独特组合。这项工作的长期目标是提供一套设计规则，以优化各种纳米结构材料的光电转换。几个对开发最佳光电转换设计规则至关重要的基本问题将得到解决，包括：与点缺陷集合相关的电子状态与小量子点的电子状态相似的临界长度尺度是什么？QD的形状和大小如何影响QD电子态？界面无序和应变如何影响二维和三维量子点阵列中量子点电子态的耦合以及电子微带的形成？为了优化光电转换效率，需要哪种小频段架构？利用co- pi在最先进的纳米制造、前所未有的空间分辨率测量和多尺度模拟方面的独特专业知识，将开发一套设计规则，以优化纳米结构中间波段太阳能电池的光电转换。更广泛的影响：这项研究预计将对能源和可持续性产生重大影响。这些私人机构还将在能源和可持续性方面制定一项外联计划。拓展项目将在当地公立高中建立伙伴关系。这种方法将为安娜堡的联合项目开发的一个更雄心勃勃的推广计划奠定基础，该计划已将30多名当地高中生带到UM校园进行暑期研究实习。pi将开发一个名为“太阳能电池材料”的模块，并将其纳入现有的高中物理和化学课程。他们将向来自不同学校系统的不同背景的学生展示这个互动和实践模块。该模块将利用UIUC和UM在可持续能源研究方面的重大新举措，并将有助于产生对工程研究的兴趣。

0933348JohnsonSummaryTechnical Merit: Intermediate-band (IB) solar cells have the potential to convert sunlight to electricity with record efficiency. Perhaps the most promising approach to IB semiconductors is quantum dot (QD) arrays. In principle, these QD arrays would replace the intrinsic region in state-of-the-art p-i-n solar cells. Although this concept was originally proposed in the 1990s, the anticipated efficiency records have yet to be achieved. The performance to date has been limited by a lack of fundamental design rules for energy conversion processes in the context of QD confined states and minibands. In particular, an understanding of the influence of QD shapes, sizes, strain states, and QD/matrix interface uniformity on the formation of and interaction between QD confined states and minibands is needed. Furthermore, novel miniband architectures which enable optimum sunlight to electricity conversion efficiencies must be developed. The proposed approach involves a unique combination of state-of-the-art nanofabrication methods, measurements with unprecedented spatial resolution, and multi-scale simulations. The long-term objective of the work is to provide a set of design rules to optimize sunlight-to-electricity conversion in a wide variety of nanostructured materials. Several fundamental questions critical to the development of optimum sunlight-to-electricity conversion design rules will be addressed, including: what is the critical length scale at which the electronic states associated with a collection of point defects appear similar to those of a small QD? How do QD shapes and sizes influence the QD electronic states? How do interfacial disorder and strain influence the coupling of QD electronic states, as well as the formation of electronic mini-bands in two-dimensional and three-dimensional QD arrays? Which miniband architectures are needed to optimize the sunlight to electricity conversion efficiency? Using the unique combined expertise of the co-PIs in state-of-the-art nanofabrication, measurements with unprecedented spatial resolution, and multi-scale simulations, a set of design rules to optimize sunlight-to-electricity conversion in nanostructured intermediate band solar cells will be developed.Broader Impact: This research is expected to have a substantial impact on energy and sustainability. The PIs will also develop an outreach program in energy and sustainability. The outreach program will build partnerships in the local public high schools. This approach will lay the groundwork for a more ambitious outreach program developed by the co-PI in Ann Arbor, which has brought more than 30 local high school students to the UM campus for summer research internships. The PIs will develop a module, 'Materials for Solar Cells", to be incorporated into existing high school physics and chemistry courses. They will present this interactive and hands-on module to students from various backgrounds within several school systems. The module will draw on the excitement surrounding major new initiatives at UIUC and UM in sustainable energy research, and will serve to generate interest in engineering research.