Magic-size nanoclusters as low-temperature precursors to nanocrystal and bulk semiconductor films

该项目的研究推动了半导体纳米科学在太阳能技术中的潜在应用。 由于大气中的二氧化碳（CO2）水平目前威胁着全球生态系统和人类福祉，开发清洁能源技术是一项重大的社会需求。 Buhro教授正在提供新的方法来制备更高效的太阳能电池和广泛使用太阳能电力所需的经济，可扩展的半导体加工。 该项目的一个方面是开发具有用于太阳能电池的太阳能吸收层中的电荷传输的优化结构的半导体-半导体薄膜。 这可以提高电池的性能。 这种策略的关键是纳米晶体的形状，它们是板状或带状的，并且紧密地堆叠在一起。 这些形状能够在长距离上传输电荷。 该项目的第二个方面是使用溶液化学的半导体薄膜的低温沉积。 更广泛地应用太阳能发电的一个主要缺点是，用目前的气相和真空技术制造太阳能电池的半导体元件的成本很高。 Buhro教授致力于开发更经济的基于溶液的加工方法。 该项目的两个方面都依赖于所谓的“神奇大小的半导体纳米团簇”作为关键的化学中间体和前体。 神奇大小的纳米团簇是小的离散分子单元，其具有与目标半导体相相同的组成，并且在低温下从溶液中产生晶体半导体。 通过提高电荷传输能力和超导薄膜制造的经济性，这项研究可能会产生广泛的社会影响，因为它促进了太阳能技术的可用性和实用性。 此外，Buhro教授还是许多女性博士的导师。科学家 在这个研究项目中，圣路易斯华盛顿大学的William Buhro教授得到了大分子、超分子和纳米化学（MSN）项目的支持，利用化学计量的魔法大小的半导体纳米团簇和平面（2D）胶体半导体纳米晶体来促进低温、高分子和纳米化学的发展。基于溶液的半导体加工和半导体太阳能电池。 固态量子点（QD）太阳能电池已成为第三代光伏技术，有望实现经济、可规模化生产，并具有现实应用所需的太阳能转换性能。 平面（2D）半导体纳米晶体（量子带和量子片晶）具有与胶体量子点相当的光学性质和界面特性。 它们还具有至少一个延伸长度尺寸。 Buhro教授现在正在研究它们在太阳能吸收层中的应用。 二维电致伸缩薄膜的结构由三维取向的半有序畴组成。 相对于QD的更大的横向尺寸预期增加载流子平均自由程并最小化跳跃。 整个膜结构可以提供在所有三个维度上均为扁平的传导路径。这些材料可使载流子复合最小化并增加太阳能电池的光子转换效率。 该项目的第二部分涉及分子半导体油墨。 用于半导体制造的理想分子油墨应具有与目标半导体匹配的化学计量、动力学不稳定配体以及低温半导体结晶的能力。 Buhro教授正在为此目的研究新分离的化学计量大小的II-VI纳米团簇。 采用这种纳米团簇作为低温前体大块多晶半导体薄膜的策略正在研究中。 努力完成这些化学计量，胺钝化，神奇的大小II-VI纳米团簇的结构表征，并探索其化学反应性和物理性质也正在进行中。 该项目的研究有望从根本上推动半导体纳米科学对太阳能技术的影响。 此外，Buhro教授指导了大量女性博士。科学家，并正在努力通过将主动学习策略纳入STEM入门课程来留住女性。

The research pursued in this project advances semiconductor nanoscience for potential use in solar-energy technologies. As atmospheric carbon dioxide (CO2) levels currently threaten the global ecosystem and human well-being, the development of clean-energy technologies is a major societal necessity. Professor Buhro is providing new methods to prepare more-efficient solar cells and the economical, scalable semiconductor processing required for widespread access to solar electricity. One aspect of the project is to develop semiconductor-nanocrystal films having optimized structures for charge transport in the solar-absorber layers of solar cells. This may increase the performance of the cells. The key to this strategy is the shape of the nanocrystals, which are plate-like or ribbon-like, and stack together compactly. These shapes are capable of transporting charge over large distances. A second aspect of the project is the low-temperature deposition of semiconductor films using solution chemistry. A major drawback to the wider implementation of solar electricity is the high cost of making the semiconductor components of solar cells by the current gas-phase and vacuum-based technologies. Professor Buhro is contributing to the development of much more economical solution-based processing methods. Both aspects of the project rely on so-called "magic-size semiconductor nanoclusters" as key chemical intermediates and precursors. The magic-size nanoclusters are small, discrete molecular units that have the same compositions as the target semiconductor phases, and that produce crystalline semiconductors from solution at low temperatures. By increasing the ability to transport charge and the economy of semiconductor-film fabrication, this research may have broad societal impact as it promotes the availability and practicality of solar-energy technology. Additionally, Professor Buhro is a mentor to a large number female Ph.D. scientists. He works to retain women in STEM fields by incorporating active-learning strategies in introductory courses.In this research project, Professor William Buhro of Washington University in St. Louis is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) program to employ stoichiometric magic-size semiconductor nanoclusters and flat (2D), colloidal semiconductor nanocrystals in the advancement of low-temperature, solution-based semiconductor processing and nanocrystal solar cells. Solid-state quantum-dot (QD) solar cells have emerged as a third-generation photovoltaic technology that promises economical, scalable production, and the necessary solar-conversion performance for real-world application. Flat (2D) semiconductor nanocrystals (quantum belts and quantum platelets) have optical properties and interfacial characteristics comparable to colloidal quantum dots. They also have at least one extended length dimension. Professor Buhro is now investigating their use in nanocrystal solar-absorber layers. The architectures of 2D-nanocrystal films consist of bundled semi-ordered domains oriented in three dimensions. The larger lateral nanocrystal dimensions relative to QDs are expected to increase the carrier mean free paths and minimize hopping. The overall film architecture may provide conduction pathways percolating in all three dimensions. These materials may minimizing carrier recombination and increasing the photon-conversion efficiencies of solar cells. A second component of this project addresses molecular semiconductor inks. Ideal molecular inks for semiconductor fabrication should possess stoichiometries matched to the target semiconductor, kinetically labile ligands, and the capacity for low-temperature semiconductor crystallization. Professor Buhro is investigating the newly isolated, stoichiometric magic-size II-VI nanoclusters for this purpose. Strategies for employing such nanoclusters as low-temperature precursors to bulk, polycrystalline semiconductor films are under study. Efforts to complete the structural characterization of these stoichiometric, amine-passivated, magic-size II-VI nanoclusters, and to explore their chemical reactivities and physical properties are also underway. The research pursued in this project is expected to fundamentally advance semiconductor nanoscience impacting solar-energy technologies. Additionally, Professor Buhro mentors a large number female Ph.D. scientists, and is working to retain women by incorporating active-learning strategies into introductory STEM courses.