Synthesis, Defect Structure and Photo-physics of Ternary Pnictide Nanocrystals

非技术概述光子和光电子应用消耗了近30%的生产能源。预计将产生最大影响的两项环保光子技术是用于节能照明的固态光源(发光二极管(LED))和用于产生太阳能发电的光伏(PV)。目前主导光电子市场的材料是不可持续的，并遇到了稳定性问题，使用镉、碲或铅等有毒材料，或稀有而昂贵的元素如铟或镓。经济上可行的解决方案依赖于发现可扩展、低成本、富含地球的低毒材料(符合RoHS)，并且开发和集成到应用中所需的能量投入最少。在NSF材料研究部固态和材料化学计划的支持下，Ayaskanta Sahu教授和纽约大学及其研究小组将研究生产由地球丰富、低成本、无毒元素(如锌、锡、磷化物)组成的三元稀土纳米晶的方法，这些元素适合大规模、可持续的生产。这一综合研究和教育计划旨在推动在发现和开发这种未被探索的新一代光子纳米结构方面取得根本性进展，加快涉及这些材料的技术创新，并扩大纳米科学的前沿。主要目的是对复杂材料体系的各种溶液生长机制和合成过程提供详细的见解，从而推动纳米晶体合成领域的发展，并为多组分纳米晶体体系的合理设计和在功能光子器件中的应用提供途径。该项目涉及材料科学、工程、化学和物理，提供了一个多元化的平台，以参与、培训和教育从K-12学生到本科生和研究生的下一代工程师和科学家，并灌输积极合作的文化。该项目还提供了一个补充的教育和外联Nexus计划，该计划致力于增加妇女、黑人和拉丁裔学生以及其他代表不足的少数族裔(URM)的研究参与度和促进跨学科环境，并涉及为URM学生开发以教学为导向的积极动手学习工具包，供在K-12暑期科学夏令营和纽约市学校和美国合作机构的研讨会上演示。本项目得到美国国家科学基金会材料研究部固态与材料化学项目的支持，旨在合成可持续的三元胶体量子点II-IV-V2(II=锌、镁、锶；IV=硅、锡、锗；V=N、P)胶体量子点，了解单个胶体量子点的复杂相行为、缺陷结构以及阳离子无序对这些胶体量子点组件的光物理影响，并控制II-IV-V2薄膜的光电性质，从而能够制造出高效的发光和捕光光子器件。与作为光子应用的主力的III-V相比，II-IV-V2量子量子点由于量子限制而具有可调的带隙，估计具有减少的电荷分离效应，这有望导致改善光电性能，并且与现有技术兼容。此外，与存在混溶问题的二元III-V相比，这些材料既可以简化p型掺杂(III-VS的巨大问题)，也可以通过阳离子无序和成分控制实现带隙可调。本项目旨在建立一个系统的三元化合物CQD的合成和CQD组装的薄膜沉积过程，并辅以物理、光谱和分析表征(原位和非原位)技术，以阐明CQD的结构(有序/无序相和缺陷)、光学(量子限制)和电子性质，并就合成条件和微晶尺寸对薄膜性能的影响提供反馈和指导。因此，这种紧密耦合的合成-结构-性能-性能协同反馈回路提供了对II-IV-V2量子点缺陷结构和光电性质的详细了解。该项目有三个相互关联的目标和任务：(1)合成三元II-IV-V2(ZnSnP2)CQD，(2)对三元PNictid CQD中无序和本征缺陷浓度的调制，以及(3)PNictid CQD的结构、光学和电学表征。旨在同时和协同地整合所有这些任务，以实现II-IV-V2半导体纳米结构的材料科学和工程方面的关键突破。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical SummaryPhotonic and optoelectronic applications consume nearly 30% of all energy produced. The two environmentally friendly photonic technologies expected to have the largest impact are solid-state light sources (light emitting diodes (LEDs)) for energy efficient lighting, and photovoltaics (PVs) for generating solar electricity. Materials currently dominating the photonics market are not sustainable and run into issues with stability, use of toxic materials such as cadmium, tellurium or lead, or rare and expensive elements such as indium or gallium. An economically viable solution relies on discovery of scalable and low-cost earth-abundant materials with low toxicity (RoHS compliant) and requiring minimal energy input for both development and integration into applications. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, Prof. Ayaskanta Sahu and New York University and his research group will investigate methods to produce ternary pnictides nanocrystals comprising of earth-abundant, low-cost, non-toxic elements (e.g. zinc tin phosphide) amenable to large-scale, sustainable production. This integrated research and education program aims to drive fundamental advances in the discovery and development of this new generation of unexplored photonic nanostructures, accelerating technological innovations involving these materials and expanding the frontiers of nanoscience. The primary goal is to provide detailed insight into various solution-growth mechanisms and synthetic procedures for complex material systems, thus advancing the field of nanocrystal synthesis and providing a pathway for rational design and incorporation of multicomponent nano-crystalline systems in functional photonic devices. This project involving materials science, engineering, chemistry and physics, offers a diverse platform to engage, train and educate the next generation of engineers and scientists starting from K-12 students to undergraduates and graduate students, and instill a culture of active collaboration. The project also provides a complementary education and outreach NEXUS program that strives to increase research participation and promote an interdisciplinary environment for women, black and Latino students, and other underrepresented minorities (URMs), and involves developing an instruction-oriented active hands-on learning kit by URM students for demonstration in K-12 Summer Science Camps and workshops at New York City schools and partner institutions in the United States. Technical SummaryThis project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, aims to synthesize sustainable ternary II-IV-V2 (II = Zn, Mg, Sr; IV = Si, Sn, Ge; V = N, P) colloidal quantum dots (CQDs), understand the complex phase behavior, defect structure and effect of cation disorder on the photo-physics of individual CQDs and assemblies of these CQDs, and control the optoelectronic properties of II-IV-V2 films to such an extent that fabrication of light-emitting and light harvesting photonic devices that will achieve high efficiencies is enabled. Compared to the III-Vs, which are the workhorses of photonic applications, II-IV-V2 CQDs, with tunable band gaps owing to quantum confinement, are estimated to exhibit reduced charge separation effects which is expected to lead to improved optoelectronic properties, and are compatible with existing technologies. In addition, these materials allow for both ease of p-type doping (huge issue with III-Vs) as well as band gap tunability via cation disorder and compositional control in contrast to binary III-Vs which suffer from miscibility issues. This project aims to establish a systematic process of ternary pnictide CQD synthesis and thin-film deposition of assemblies of CQDs, accompanied by complementary physical, spectroscopic and analytic characterization (both in-situ and ex-situ) techniques to elucidate the structure (order/disorder phases and defects), optical (quantum confinement) and electronic properties and provide feedback and guidance on the effects of synthesis conditions and crystallite size on film performance. Thus, this close-knit coupled synergistic feedback loop of synthesis-structure-property-performance provides a detailed understanding of the defect structure and optoelectronic properties of II-IV-V2 CQDs. The project has three interrelated objectives and tasks: (1) Synthesis of ternary II-IV-V2 (ZnSnP2) CQDs, (2) Modulation of disorder and intrinsic defect concentration in ternary pnictide CQDs, and (3) Structural, optical and electrical characterization of pnictide CQDs. Efforts are directed to integrate all these tasks simultaneously and synergistically to enable crucial breakthroughs in the materials science and engineering of II-IV-V2 based semiconductor nanostructures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.