Lead free organic-inorganic halide perovskite ferroelectrics with large piezoelectric responses

非技术描述：铁电性描述了某些材料对外部电场的自发电响应。柔性铁电薄膜是低成本可穿戴传感器、能量转换系统和个人电子产品的有吸引力的候选者。然而，目前用于此类应用的材料是陶瓷，其柔韧性不够，并且含有有毒的铅元素。最近，一种新发现的无铅柔性有机-无机钙钛矿铁电材料显示出与传统刚性陶瓷薄膜相媲美的性能。本项目旨在探索在这种新型有机-无机材料中观察到的铁电性能的来源，并设计出具有改进性能的这类新材料。该项目旨在开发使用这种新开发的铁电材料生产实用可穿戴和可植入铁电设备的技术。理论研究和实验综合的综合性质培养了研究生和本科生的跨学科技能，这对于在新兴的可穿戴和植入式设备领域开发创新解决方案至关重要。研究结果预计将通过俄亥俄州托莱多大学的赖特光伏创新和商业化中心向公众公布。技术描述：该项目包括对有机-无机三甲基氯甲基铵三氯锰（TMCM-TCM）钙钛矿中观察到的大压电系数的机理进行理论和实验研究，以及开发沉积高质量TMCM-TCM钙钛矿薄膜的合成方法。理论研究的重点是利用密度泛函理论计算了解TMCM分子、无机骨架及其耦合如何影响TMCM- tcm的铁电性和压电系数。理论研究还包括寻找其他分子和无机八面体框架，这些框架可以形成具有增强铁电性和压电系数的新型有机-无机钙钛矿材料。此外，理论研究还揭示了点缺陷和晶格缺陷对铁电性能和压电性能的影响。实验研究的重点是开发旋转镀膜、叶片镀膜和真空热蒸发的合成工艺，以沉积高质量的有机-无机钙钛矿铁电薄膜。利用x射线衍射、扫描电镜、紫外可见光谱、光致发光光谱和差示扫描量热法对合成的TMCM-TCM薄膜的质量进行了关键评估。实验部分还研究了不同衬底对合成的TMCM-TCM薄膜晶粒尺寸、晶粒取向、表面粗糙度、缺陷密度和均匀性的影响。如果成功，结果将为实现高效可穿戴和可植入的铁电和压电器件提供途径。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 Description: Ferroelectricity describes the spontaneous electric response of certain materials to external electric field. Flexible ferroelectric thin films are attractive candidates for use in low-cost wearable sensors, energy conversion systems, and personal electronics. However, the current materials for this type of applications are ceramic, which are not sufficiently flexible and contain toxic lead element. Recently, a newly discovered, lead-free flexible organic-inorganic perovskite ferroelectric material show properties rivaling conventional rigid ceramic thin films. This project aims to explore the origin for the ferroelectric properties observed in this new organic-inorganic material and to design new materials of this type with improved properties. The project seeks to develop techniques for producing practical wearable and implantable ferroelectric devices using this newly-developed ferroelectric material. The integrative nature of theoretical investigation and experimental synthesis trains graduate and undergraduate students in cross-disciplinary skills that are essential for developing innovative solutions in the burgeoning field of wearable and implantable devices. Research results are expected to be available to the public via Ohio's Wright Center for Photovoltaics Innovation and Commercialization at The University of Toledo.Technical Description: The project includes both theoretical and experimental study of the mechanisms determining the large piezoelectric coefficient observed in organic-inorganic trimethylchloromethyl ammonium trichloromanganese (TMCM-TCM) perovskite, as well as development of synthesis methods for depositing high quality TMCM-TCM perovskite thin films. The theoretical study focuses on understanding how the TMCM molecules, the inorganic framework and the coupling between these two affect the ferroelectricity and piezoelectric coefficient of TMCM-TCM using density functional theory calculations. The theoretical study also includes searching for other molecules and inorganic octahedral frameworks that can form new organic-inorganic perovskite materials with enhanced ferroelectricity and piezoelectric coefficients. Additionally, the theoretical study provides understanding of the influence of point defects and lattice defects on the ferroelectric and piezoelectric properties. The experimental study focuses on developing synthesis processes including spin-coating, blade-coating and vacuum-thermal evaporation to deposit high quality organic-inorganic perovskite ferroelectric thin films. Characterization efforts, employing X-ray diffraction, scanning electron microcopy, UV-Vis spectroscopy, photoluminescence spectroscopy, and differential scanning calorimetry provide key assessments on the quality of the synthesized TMCM-TCM thin films. The experimental part also includes the investigation of the influence of various substrates on grain size, grain orientation, surface roughness, defect density, and uniformity of the synthesized TMCM-TCM thin films. If successful, the results provide pathways to realize efficient wearable and implantable ferroelectric and piezoelectric devices.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.