Binary and Ternary Semiconductor Quantum Rods: A Computational Route to Next-Generation All-Inorganic Photovoltaic Materials

二元和三元半导体量子棒：下一代全无机光伏材料的计算路线

• 批准号: 0730365
• 负责人: Ramamurthy Ramprasad
• 金额: $ 20万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0730365&HistoricalAwards=false
• 关键词: Binary; Ternary; Semiconductor; Quantum; Rods

The efficiency of photovoltaic systems based on inorganic nanocrystals could far surpass that of currently used bulk thin film (e.g., Si) based architectures, as the quantum confinement in nanocrystals makes them significantly better at converting solar photons to electron-hole pairs (or excitons). Nevertheless, major challenges remain, concerning the dissociation of the exciton into electrons and holes-a necessary condition for the efficient overall conversion of solar to electrical energy. This proposal rests on the idea that carefully designed interfaces between materials of the right type within a quantum rod will help achieve enhanced exciton dissociation and therefore optimal photovoltaic performance. Intellectual Merit: The objective of this proposal is to use an integrated set of first principles computations based on density functional theory (DFT) to study a variety of binary and ternary quantum rod (QR) systems containing interfaces. Binary systems to be studied will include CdSe and CdTe, and ternary systems will include CdSe1-xTex, Cd1-xZnxSe, CdTe1-xSx, and ZnSe1-xTex. Crystal structure variation along the length of the binary systems, and composition (i.e., x value) variation along the QR radius or length will be considered so as to result in core/shell or end-contacted interfaces. The specific system choices were motivated (among other factors) by their potential for the creation of staggered Type II valence and conduction band edge offsets at interfaces. Engineering such Type II band offsets will be critical to increasing the extent of exciton dissociation. DFT computations will be used to assess the stability and electronic structure of these systems as a function of quantum confinement (i.e., QR radius) and the rapidity of composition variations across the interface. The DFT electronic eigenvalues and wavefunctions will then be used to investigate critical properties related to exciton dissociation such as variations in the band edge positions across interfaces, electron-hole binding energy as a function of electron and hole wavefunction position, barriers to exciton dissociation and exciton recombination lifetime. Broader Impact: An important component of this proposal is the education of students. The industrial experience of the PI will enhance the engineering education of students and will aid in broadening student exposure beyond the academic environment through interactions with industry (via internships, visits and joint publications). The PI will continue to refine and teach a Computational Materials Science course he developed in 2006, which is filling a gap in the current curricula of the Engineering, Physics and Chemistry departments at the UConn. Outreach activities will be fostered to increase public awareness in the areas of Alternative Energy Solutions and Nanotechnology, in collaboration with local establishments committed to community services (e.g., public libraries and museums). In particular, the PI has the strong support of the Tolland Public Library and local middle/high school teachers, in aiding his outreach efforts, and in packaging and propagating the excitement of his research, and of Science & Engineering in general, to the local communities.

基于无机纳米晶体的光伏系统的效率可能远远超过目前使用的基于大块薄膜（例如Si）的架构，因为纳米晶体中的量子约束使它们在将太阳光子转换为电子-空穴对（或激子）方面表现得更好。然而，主要的挑战仍然存在，关于激子解离成电子和空穴——这是太阳能到电能有效全面转换的必要条件。该提议基于这样一种想法，即在量子棒内精心设计合适类型的材料之间的界面将有助于实现增强的激子解离，从而实现最佳的光伏性能。智力优势：本提案的目标是使用基于密度泛函理论（DFT）的一套综合第一性原理计算来研究各种包含界面的二元和三元量子棒（QR）系统。所研究的二元体系包括CdSe和CdTe，三元体系包括CdSe1-xTex、Cd1-xZnxSe、CdTe1-xSx和ZnSe1-xTex。考虑晶体结构沿二元体系长度的变化，以及组成（即x值）沿QR半径或长度的变化，从而产生核/壳或端接触界面。具体系统选择的动机（除其他因素外）是由于它们在界面处产生交错型价和导带边缘偏移的潜力。工程这样的II型波段偏移将是增加激子解离程度的关键。DFT计算将用于评估这些系统的稳定性和电子结构，作为量子约束（即QR半径）的函数和组成在界面上变化的速度。然后，DFT电子特征值和波函数将用于研究与激子解离相关的关键特性，如带边位置在界面上的变化，电子-空穴结合能作为电子和空穴波函数位置的函数，激子解离的障碍和激子复合寿命。更广泛的影响：该提案的一个重要组成部分是对学生的教育。PI的工业经验将加强学生的工程教育，并将通过与工业的互动（通过实习，访问和联合出版物）帮助扩大学生在学术环境之外的接触。PI将继续完善和教授他在2006年开发的计算材料科学课程，该课程填补了康涅狄格大学工程、物理和化学系目前课程的空白。将与致力于社区服务的地方机构（例如公共图书馆和博物馆）合作，促进外联活动，以提高公众对替代能源解决方案和纳米技术领域的认识。特别值得一提的是，PI得到了托兰公共图书馆和当地初中/高中教师的大力支持，协助他的外联工作，并向当地社区包装和宣传他的研究以及科学与工程的兴奋之处。