Excellence in Research: 3D Printed Radiation Detectors with Perovskite-Polymer Composites

目前用于核材料测定的辐射探测器使用的是在高温下加工的无机单晶，很难扩大到大尺寸。要获得高精度和高效率地探测感兴趣的核材料，包括高浓缩铀和钚-239，特别是在移动的货物中，探测器尺寸大是必不可少的。大面积和低成本的辐射探测器还将提高许多工业采矿和冶金过程的运行效率和质量控制。此外，核医学诊断和外层空间粒子物理研究都需要像素化辐射探测器阵列。目前的无机单晶探测器阵列由于难以加工成小尺寸的像素并组装成致密的探测器阵列而受到空间分辨率的限制。为了解决这些挑战，该团队的目标是开发新的半导体-聚合物复合材料，以取代用于辐射探测器和探测器阵列的传统单晶。如果成功，与无机单晶材料相比，复合材料将具有巨大的加工和制造优势，例如，通过溶液浇注、热压、熔融挤出和注塑等方法，可以像商品塑料一样加工，获得大尺寸和各种形状的辐射探测器，或者通过3D打印，获得具有前所未有的高空间分辨率和制造灵活性的探测器阵列。技术总结：该项目将研究一组有机金属卤化物钙钛矿(钙钛矿)半导体及其聚合物基复合材料。最先进的钙钛矿型半导体具有长载流子寿命和高载流子迁移率，含有高原子序数元素(铯、铅和碘)，并具有高辐射硬度，使其成为辐射探测器应用的理想选择。此外，它们可以很容易地溶解在许多有机溶剂中，有助于为这一拟议的项目配制钙钛矿-聚合物复合材料。这些工作将有助于对卤化物钙钛矿-聚合物复合材料的结构、加工和性能关系的基本了解，包括：1)如何设计钙钛矿和聚合物相之间的化学界面，以提高钙钛矿晶体的分散性和抑制离子电荷迁移；以及2)如何设计复合材料中的电子界面，以增强和平衡高能光子照射下的电子和空穴收集。如果成功，这项工作将通过首次研究用于高分辨率像素化辐射探测器的钙钛矿-聚合物复合材料的3D打印，从而开创添加剂制造的新纪元。对复合材料中电荷传输过程的认识和工程应用，可以为未来探索其他半导体-聚合物复合材料以实现新一代大规模、低成本的光电制造提供重要的指导。该项目还将帮助在一所历史悠久的黑人公立大学(佛罗里达农业和机械大学)创建一个新的教育项目，培训代表不足的工程专业学生，为制造业、电子、半导体和国家安全行业的劳动力管道提供燃料。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。

Current radiation detectors for nuclear material determination use inorganic single crystals that are processed at high temperatures and difficult to scale up to large sizes. A large detector size is essential for obtaining high accuracy and efficiency for detecting nuclear materials of interest including highly enriched uranium and plutonium-239 especially in a moving cargo. Large area and low-cost radiation detectors will also enhance operation efficiency and improve quality control of many industrial mining and metallurgical processes. In addition, pixelated radiation detector arrays are required for nuclear medical diagnostics and for the study of particle physics in outer space. Current detector arrays with inorganic single crystals have suffered from a limited spatial resolution due to the difficulties of machining these single crystals into small size pixels and assembling them into dense detector arrays. To solve these challenges, the team aims to develop new semiconductor-polymer composites as a replacement of the conventional single crystals for radiation detectors and detector arrays. If successful, there will be tremendous processing and manufacturing advantages of the composites compared with their inorganic single crystal counterparts, for instance, the composites can be potentially processed like commodity plastics by solution casting, hot pressing, melt extrusion and injection molding to achieve radiation detectors with large sizes and various shapes, or by 3D printing to achieve detector arrays with an unprecedented high spatial resolution and manufacturing flexibility.Technical summary:The project will investigate a group of organometal halide perovskite (perovskite) semiconductors and their polymer matrix composites. The state-of-the-art perovskite semiconductors exhibit a long charge carrier lifetime and high carrier mobility, contain high atomic number elements (cesium, lead, and iodine), and have a high radiation hardness, making them ideal candidates for radiation detector application. Moreover, they can be readily dissolved in many organic solvents, facilitating the formulation of perovskite-polymer composites for this proposed project. The work will lead to fundamental understanding of the structure, processing, and property relationships of halide perovskite-polymer composites including, 1) how to engineer the chemical interfaces between the perovskite and polymer phases to improve perovskite crystal dispersity and suppress ionic charge migration; and 2) how to engineer the electronic interfaces in the composite to enhance and balance both electron and hole collection upon irradiation of high energy photons. If successful, the work will establish a new era of additive manufacturing by investigating for the first time the 3D printing of perovskite-polymer composites for high-resolution pixelated radiation detectors. The knowledge of understanding and engineering charge transport processes in the composites can provide importance guidance for future exploration of other semiconductor-polymer composites for new generation large scale, low-cost optoelectronic manufacturing. This project will also help create a new educational program at a historically black public university (Florida Agricultural and Mechanical University) for the training of underrepresented engineering students to fuel the workforce pipeline in manufacturing, electronics, semiconductors, and national security industries.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.