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

光子和光电应用消耗了近30%的能源。预计影响最大的两种环境友好型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。经济上可行的解决方案依赖于发现可扩展且低成本的低毒性（符合RoHS标准）的地球丰富材料，并且在开发和集成应用过程中需要最少的能源投入。在美国国家科学基金会材料研究部固态和材料化学项目的支持下，Ayaskanta Sahu教授和纽约大学及其研究小组将研究生产三元镍纳米晶体的方法，该纳米晶体由地球上丰富的、低成本的、无毒的元素（如锌锡磷化物）组成，适合大规模、可持续生产。这项综合研究和教育计划旨在推动新一代未开发的光子纳米结构的发现和发展的根本进步，加速涉及这些材料的技术创新，扩大纳米科学的前沿。主要目标是为复杂材料系统的各种溶液生长机制和合成过程提供详细的见解，从而推进纳米晶体合成领域，并为在功能光子器件中合理设计和结合多组分纳米晶体系统提供途径。该项目涉及材料科学、工程、化学和物理，为从K-12学生到本科生和研究生的下一代工程师和科学家提供了一个多元化的平台，并灌输了积极合作的文化。该项目还提供了一个补充教育和外展NEXUS项目，旨在提高研究参与度，为妇女、黑人和拉丁裔学生以及其他代表性不足的少数民族（URM）创造一个跨学科的环境，并为URM学生开发一套以教学为导向的积极实践学习工具包，用于在纽约市学校和美国合作机构的K-12暑期科学营和讲习班中进行示范。本项目由美国国家科学基金会材料研究部固态与材料化学项目资助，旨在合成可持续三元化合物II-IV- v2 (II = Zn, Mg, Sr; IV = Si, Sn, Ge；V = N， P)胶体量子点（CQDs），了解复杂的相位行为，缺陷结构和阳离子无序对单个CQDs及其组件的光物理的影响，并控制II-IV-V2薄膜的光电特性，从而使制造能够实现高效率的发光和光收获光子器件成为可能。与光子应用的主推器iii - v相比，由于量子约束而具有可调谐带隙的II-IV-V2 CQDs估计会表现出减少的电荷分离效应，这有望改善光电性能，并与现有技术兼容。此外，这些材料允许易于p型掺杂（iii - v的巨大问题），以及通过阳离子无序和成分控制的带隙可调性，与遭受混相问题的二元iii - v相比。本项目旨在建立一个系统的三元镍基CQD合成过程和CQD组件的薄膜沉积，并结合互补的物理、光谱和分析表征（原位和非原位）技术来阐明结构（有序/无序相和缺陷）、光学（量子约束）和电子特性，并就合成条件和晶体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-性能的协同反馈回路提供了对II-IV-V2 CQDs缺陷结构和光电性能的详细了解。该项目有三个相互关联的目标和任务：(1)三元II-IV-V2 (ZnSnP2) CQDs的合成；(2)三元pnictide CQDs中无序和固有缺陷浓度的调制；(3)pnictide CQDs的结构、光学和电学表征。努力的方向是同时和协同地整合所有这些任务，以实现基于II-IV-V2的半导体纳米结构的材料科学和工程的关键突破。该奖项反映了美国国家科学基金会的法定使命，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.