Unveiling intrinsic functionality of two-dimensional organic-inorganic ferroelectrics for energy storing/converting devices: integrated computational-experimental approach

非技术性：钙钛矿是一类重要的材料，在发光二极管和太阳能电池等设备中显示出了良好的前景。一些无机钙钛矿材料同时表现出铁电性、压电性和热释电性的奇异性质。这些现象以及将机械能和热能转换为电能的技术都具有极大的科学价值。这使得传感器、执行器、能量采集、数据存储和光电子学等应用变得多样化。目前的技术主要是基于无机钙钛矿，但这些材料有缺点。这些问题包括高温加工、缺乏机械灵活性、高成本，以及在某些情况下存在有毒元素。最近，一类新的具有有机和无机成分的混合钙钛矿出现了，关于铁电性和压电性的证据耐人寻味，但往往存在争议。该项目旨在通过综合实验-理论方法实现对混合型钙钛矿的基本理解。重点将放在块状和低维混合钙钛矿的铁电性、压电性、相关相变和紧急器件功能上。这项研究可能导致发现铁电性、压电性的新形式或表现形式，以及这些现象如何受到相变的影响。这些研究有可能改变我们目前对有机材料的理解，并揭示它们的性能和设备功能是否与无机材料相当，甚至超过无机材料。这反过来可能创造出一条通往具有新功能和能量转换特性的设备的途径，并将其技术应用推向一个新的水平。该项目还将大力促进对STEM工作人员的培训，重点是吸纳来自代表性不足群体的学生。该项目将让本科生参与研究，并丰富物理和化学课程。将通过对当地小学和中学进行有组织的实地考察来开展外联活动。技术：该项目旨在实现以下具体目标。目的1：通过多尺度第一性原理模拟、合成和单晶样品的综合结构和电学表征，建立复合三维有机-无机钙钛矿铁电性的机理，揭示相关相变的本质。目的2：通过最先进的计算和实验相结合的方法，揭示这些材料中的铁电性和压电性机制和表现如何在纳米尺度上发生变化。目的：探索这些新型材料的铁电和压电性能的机械可调性，并揭示它们集成在储能和转换装置中的可能性。目标4：参与广泛的教育和外联活动，以促进建立一支世界级的多样化的材料科学和工程工作人员队伍，并为在学术界或工业界的职业生涯进行培训。该项目的预期成果包括：潜在地发现块状和二维混合钙钛矿中铁电和压电性的新形式，在这些材料中建立铁电性和压电性的机制，它们的全面结构和电学表征，阐明相关相变的性质和起源，用于它们探索和设计的计算方法和软件，预测它们在储能设备中的功能，以及纳米电容器和/或力/位移(Nano)传感器的原型。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。

Nontechnical:Perovskites are an important class of materials that have shown promise in devices such as light-emitting diodes and solar cells. Some inorganic perovskites simultaneously exhibit the exotic properties of ferroelectricity, piezoelectricity and pyroelectricity. These phenomena are of great scientific interest as well as technologies for conversion of mechanical and thermal energy to electrical power. This allows for diverse applications such as sensors, actuators, energy harvesting, data storage, and optoelectronics. Current technologies are based heavily on inorganic perovskites, but these materials have shortcomings. These include high temperature processing, lack of mechanical flexibility, high costs, and the presence of toxic elements in some cases. Very recently, a new class of hybrid perovskites with organic and inorganic components has emerged with intriguing, but often controversial, evidence for ferroelectricity and piezoelectricity. This project aims to achieve a fundamental understanding of hybrid perovskites through an integrated experimental-theoretical approach. The focus will be on ferroelectricity, piezoelectricity, associated phase transitions and emergent device functionalities of bulk and low-dimensional hybrid perovskites. The research could lead to the discovery of novel forms or manifestations of ferroelectricity, piezoelectricity and how these phenomena are affected by phase transitions. These studies have the potential to transform our current understanding of organic materials and reveal if they exhibit properties and device functionality on par with or even exceeding those of inorganic materials. This in turn could create a route to devices with novel functionality and energy converting properties, and push their technological applications to a new level. The project will also contribute strongly to the training of the STEM workforce with a focus on including students from underrepresented groups. The project will involve undergraduate students in research and enrich the Physics and Chemistry curricula. Outreach will be conducted through organized field trips to local elementary and middle schools.Technical:The project aims to address the following specific objectives. Objective 1: to establish the mechanism for ferroelectricity and uncover the nature of the associated phase transitions in hybrid three-dimensional organic-inorganic perovskites through a combination of multiscale first-principles simulations, synthesis and comprehensive structural and electrical characterization of single crystalline samples. Objective 2: to reveal how ferroelectricity and piezoelectricity mechanisms and manifestations in these materials change at the nanoscale through a combination of state-of-the-art computational and experimental approaches. Objective 3: to explore mechanical tunability of ferroelectric and piezoelectric properties of these novel materials and reveal the possibility of their integration in energy storing and converting devices. Objective 4: to engage in a wide range of educational and outreach activities in order to contribute to creating a world-class diverse materials science and engineering workforce that is trained for careers in academia or industry. The expected outcomes of the project include: potential discovery of novel forms of ferroelectricity and piezoelectricity in bulk and two-dimensional hybrid perovskites, establishment of mechanisms for ferroelectricity and piezoelectricity in these materials, their comprehensive structural and electric characterization, elucidation of the nature and origin of associated phase transitions, computational methodology and software for their exploration and design, predicting their functionality in energy storing devices, and prototypes for nanocapacitor and/or force/displacement (nano)sensors.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.