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

非技术概述光子和光电应用消耗了近30%的能源。预计将产生最大影响的两种环保光子技术是用于节能照明的固态光源（发光二极管（LED））和用于产生太阳能电力的光伏（PV）。目前主导光子市场的材料是不可持续的，并且会遇到稳定性问题，使用有毒材料，如镉，碲或铅，或稀有和昂贵的元素，如铟或镓。一个经济上可行的解决方案依赖于发现可扩展的和低成本的地球丰富的材料，具有低毒性（符合RoHS标准），并需要最小的能源投入的开发和集成到应用程序。通过这个项目，由NSF材料研究部的固态和材料化学计划支持，Ayaskanta Sahu教授和纽约大学及其研究小组将研究生产三元磷属元素的方法。 该综合研究和教育计划旨在推动新一代未开发光子纳米结构的发现和开发的根本性进展，加速涉及这些材料的技术创新并扩大纳米科学的前沿。主要目标是提供详细的洞察各种溶液生长机制和复杂材料系统的合成程序，从而推进纳米晶体合成领域，并提供一个合理的设计和多组分纳米晶体系统的功能光子器件的结合途径。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，以吸引，培训和教育下一代工程师和科学家，从K-12学生到本科生和研究生，并灌输积极合作的文化。该项目还提供了一个补充教育和外展NEXUS计划，努力提高研究参与，促进妇女，黑人和拉丁裔学生，以及其他代表性不足的少数民族（URM）的跨学科环境，包括由大学资源管理学院的学生制作一套以学习为导向的主动实践学习套件，在美国纽约市学校和伙伴机构举办12次暑期科学营和讲习班。该项目由NSF材料研究部的固态和材料化学计划支持，旨在合成可持续的三元II-IV-V2（II = Zn、Mg、Sr; IV = Si、Sn、Ge; V = N，P）胶体量子点（CQD），了解复杂的相行为，缺陷结构和阳离子无序对单个CQD和这些CQD的组装的光物理的影响，并将II-IV-V2膜的光电性质控制到能够制造将实现高效率的发光和光捕获光子器件的程度。与光子应用的主力III-V族相比，由于量子限制而具有可调带隙的II-IV-V2 CQD估计表现出减少的电荷分离效应，这有望导致改善的光电性能，并且与现有技术兼容。此外，这些材料允许容易的p型掺杂（III-V族的巨大问题）以及通过阳离子无序和组成控制的带隙可调谐性，这与遭受可调谐性问题的二元III-V族形成对比。本计画旨在建立一套系统的三元磷属元素化合物CQD的合成与薄膜沉积的方法，并辅以物理、光谱与分析的表征（原位和非原位）技术来阐明结构（有序/无序相和缺陷），光学（量子限制）和电子性质，并提供关于合成条件和微晶尺寸对膜性能的影响的反馈和指导。因此，这种合成-结构-性质-性能的紧密耦合的协同反馈回路提供了对II-IV-V2 CQD的缺陷结构和光电性质的详细理解。该项目有三个相互关联的目标和任务：（1）II-IV-V2（ZnSnP 2）三元CQDs的合成，（2）三元磷属元素化合物CQDs中的无序和本征缺陷浓度的调制，和（3）磷属元素化合物CQDs的结构、光学和电学表征。致力于同时整合所有这些任务，并协同工作，以实现材料科学和II-IV-V2基半导体纳米结构工程的重大突破。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.