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)半导体是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所需特性，这样的系统已经为下一代太阳能电池、发光设备和光电探测器提供了出色的性能。目前的HOIP研究一般集中在晶态，在晶态中，组成原子以周期性和有序的方式重复。在NSF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最先进水平的HOIP的方法，以演示和了解如何通过可访问的熔体和玻璃状态在HOIP中引入可控无序，以及如何利用这种无序来显著扩展HOIP家族的属性范围。这类研究的目标是创建设计规则，以指导可熔化和玻璃成型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差异。晶态和玻璃态之间的可逆转换，利用微小的温度变化，极大地拓宽了HOIP的潜在应用空间，包括低功率相变存储器、神经形态计算、先进传感和可重构光子学。这项研究与教育和外展密切相关。包括本科生、研究生和博士后研究人员参与国家实验室的结构-性质研究，并通过正在进行的面向学生的能源材料研讨会系列向更广泛的学生群体传达这一经验。玻璃的结构-性质数据通过一个以钙钛矿为重点的数据库向社区广泛提供，代表了HOIP玻璃状态数据的第一个集合。项目研究通过NSF REU，“纳米级侦探--阐明混合钙钛矿系统的结构和动力学”，以及通过为来自市中心和农村地区的第一代/低收入学生准备第一代/低收入学生的大学预科发展计划，将传统上服务不足的STEM社区联系起来。技术描述：该项目由NSF材料研究部的固态和材料化学计划支持，结合了有针对性的合成，以及对新型有机-无机钙钛矿(HOIP)半导体的详细结构和性能表征，该半导体提供了方便地获得熔融和玻璃态的途径，主要集中在两个关键方向。首先，该项目使用针对低HOIP熔化温度和预期玻璃晶态切换开发的设计规则进行有针对性的HOIP合成，寻求扩大能够有效访问熔体/玻璃状态的HOIP家族。利用X射线/中子散射技术、扩展X射线吸收精细结构、拉曼光谱和流变学对成功制备的材料进行了结构表征。这种密集的表征捕捉到了扩展的结晶和局部熔体/玻璃态结构，以及基本的机械性能。其次，虽然HOIP晶态属性被广泛研究和了解，但当前的项目将HOIP熔体和玻璃的局部结构与相应的热学和光电性质联系起来，使用差示扫描量热法和各种光学光谱进行研究，旨在找到一条增强和调整这些性质的途径。通过探索与HOIP熔体和玻璃状态相关的基本结构-属性联系，这项研究试图最终创建一条可预测地设计具有目标玻璃和熔体状态属性的HOIP的途径，就像结晶状态已经越来越可能的那样。该奖项反映了NSF的法定使命，并通过使用基金会的智力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.