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

基于无机纳米晶体的光伏系统的效率可以远远超过目前使用的块状薄膜（例如，Si）基架构，因为纳米晶体中的量子限制使它们在将太阳光子转换为电子-空穴对（或激子）方面明显更好。然而，主要的挑战仍然存在，关于激子分解成电子和空穴的一个必要条件，为有效的整体转换太阳能到电能。该提议基于这样的想法，即量子棒内正确类型的材料之间精心设计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：本建议的目的是使用一套完整的第一性原理计算的基础上密度泛函理论（DFT）研究各种二元和三元量子棒（QR）系统的接口。待研究的二元系统将包括CdSe和CdTe，三元系统将包括CdSe 1-xTex、Cd 1-xZnxSe、CdTe 1-xSx和ZnSe 1-xTex。晶体结构沿着二元系长度的变化，以及组成（即，x值）沿着QR半径或长度的变化，以产生核/壳或端部接触界面。具体的系统选择的动机（除其他因素外），其潜在的交错II型价带和导带边缘偏移的界面处的创建。设计这种II型能带偏移对于增加激子解离的程度将是至关重要的。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限制的函数（即，QR半径）和界面上成分变化的快速性。DFT电子本征值和波函数，然后将被用来调查激子解离相关的关键属性，如跨界面的带边位置的变化，电子-空穴结合能作为电子和空穴波函数位置的函数，激子解离和激子复合寿命的障碍。更广泛的影响：这项建议的一个重要组成部分是学生的教育。PI的工业经验将加强学生的工程教育，并将通过与行业的互动（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，这填补了康州大学工程，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）。特别是，PI有托兰公共图书馆和当地初中/高中教师的大力支持，在帮助他的推广工作，并在包装和宣传他的研究兴奋，一般的科学工程，以当地社区。

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.