Collaborative Research: Amorphous-Crystalline Switching in Organic-Inorganic Hybrid Semiconductors

非技术描述：混合有机-无机钙钛矿（HOIP）半导体代表了一种新兴的材料类别，它提供了一个独特的机会，可以在单个分子尺度的复合材料中结合和单独定制有机和无机系统的理想特性，并且这种系统已经为下一代太阳能电池，发光器件和光电探测器提供了出色的性能。目前的HOIP研究一般集中在晶体状态，其中组成原子以周期性和有序的方式重复。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，杜克大学的David Mitzi教授和科罗拉多大学的Michael Toney教授及其研究小组将研究超越当前HOIPs技术的方法，以证明和理解如何通过可接近的熔体和玻璃态在HOIPs中引入可控无序。以及如何利用这种疾病来显著扩大HOIP家族的属性范围。这些研究的目标是创建设计规则，以指导可熔融和玻璃形成hoip的未来发展，并了解玻璃和熔融状态的性质与结晶状态的不同。在晶体和玻璃状态之间的可逆切换，利用微小的温度变化，极大地扩大了hoip的潜在应用空间，包括低功耗相变存储器，神经形态计算，高级传感和可重构光子学。这项研究与教育和推广密切相关。参与的本科生、研究生和博士后研究人员与国家实验室进行结构-性质研究，并通过正在进行的以学生为导向的能源材料系列研讨会将这种经验传达给更广泛的学生群体。玻璃的结构属性数据通过以钙钛矿为中心的数据库广泛提供给社区，代表HOIP玻璃状态数据的第一个集合。项目研究通过NSF REU连接传统服务不足的STEM社区，“纳米级侦探-阐明混合钙钛矿系统的结构和动力学”，并通过大学预科发展计划，为来自内城和农村地区的第一代/低收入学生做好准备。技术描述：该项目由美国国家科学基金会材料研究部固态和材料化学项目支持，将有针对性的合成与详细的结构和性能表征相结合，用于新型有机-无机钙钛矿（HOIP）半导体，该半导体易于进入熔融态和玻璃态，重点关注两个关键方向。首先，该项目利用开发的低HOIP熔化温度和前瞻性玻璃晶体切换设计规则进行有针对性的HOIP合成，寻求扩大能够有效进入熔体/玻璃状态的HOIP系列。利用x射线/中子散射技术，结合扩展的x射线吸收精细结构，拉曼光谱和流变学，对成功创建的材料进行了结构表征。这种密集的表征捕获了扩展的晶体和局部熔融/玻璃状态结构，以及潜在的机械性能。其次，虽然HOIP晶体状态性质得到了广泛的研究和理解，但本项目将HOIP熔体和玻璃局部结构与相应的热学和光电子性质联系起来，使用差示扫描量热法和各种光谱学进行研究，寻找增强和调节这些性质的途径。通过探索与HOIP熔体和玻璃态相关的基本结构-性质联系，该研究试图最终创造一条可预测地设计具有目标玻璃和熔体状态性质的HOIP的途径，因为晶体状态已经越来越可能。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。

Nontechnical Description: Hybrid organic-inorganic perovskite (HOIP) semiconductors represent an emerging materials class that offers a unique opportunity to combine and individually tailor desirable characteristics from organic and inorganic systems within a single molecular-scale composite, and such systems already provide outstanding properties for next generation solar cells, light-emitting devices, and photodetectors. Current HOIP research generally focuses on the crystalline state, in which constituent atoms repeat in a periodic and well-ordered fashion. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, Prof. David Mitzi at Duke University and Prof. Michael Toney at the University of Colorado and their research groups will investigate methods to extend beyond the current state-of-the-art in HOIPs to demonstrate and understand how controllable disorder can be introduced within HOIPs through an accessible melt and glass state, and how this disorder can be employed to significantly expand the range of properties for the HOIP family. Such research targets creation of design rules to guide future development of meltable and glass forming HOIPs and to understand how properties of the glass and melt states differ from the crystalline state. Reversible switching between crystalline and glass states, employing small changes in temperature, vastly broadens the prospective application space for HOIPs to include low-power phase-change memory, neuromorphic computing, advanced sensing, and reconfigurable photonics. The research closely connects with education and outreach. Involved undergraduate, graduate and postdoctoral researchers engage with the national labs for structure-property studies, and this experience gets conveyed to the broader student body through an on-going student-oriented energy materials seminar series. Structure-property data for the glasses are made broadly available to the community through a perovskite-focused database, representing the first collection of HOIP glass state data. Project research connects to traditionally underserved STEM communities through an NSF REU, "Nanoscale Detectives -- Elucidating the Structure and Dynamics of Hybrid Perovskite Systems," and through a Pre-Collegiate Development Program that prepares first generation/low-income students from inner-city and rural areas.Technical Description: This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, combines targeted synthesis, with detailed structure and property characterization for a new class of hybrid organic-inorganic perovskite (HOIP) semiconductors that offers facile access to melt and glassy states, focusing on two key directions. First, the project uses targeted HOIP synthesis using developed design rules for low HOIP melting temperature and prospective glass-crystalline switching, seeking to broaden the family of HOIPs that can effectively access melt/glass states. Successfully created materials are structurally characterized using X-ray/neutron scattering techniques, coupled with extended X-ray absorption fine structure, Raman spectroscopy and rheometry. This intensive characterization captures the extended crystalline and local melt/glass state structures, as well as underlying mechanical properties. Second, while HOIP crystalline state properties are broadly studied and understood, the current project connects HOIP melt and glass local structure with corresponding thermal and optoelectronic properties, studied using differential scanning calorimetry and various optical spectroscopies, targeting a pathway for enhancing and tuning these properties. By exploring fundamental structure-property connections associated with the HOIP melt and glass states, the research seeks to ultimately create a pathway for predictably designing HOIPs with targeted glass and melt state properties, as is increasingly already possible for the crystalline state.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.