Electrically Driven Single Emissive Layer Based White Light Emitting Diodes

在过去的几十年里，白光发光二极管(WLED)已经改变了世界，在全彩色显示器和固态照明中得到了广泛的应用。然而，大多数实用的WLED是由蓝色LED(例如InGaN)芯片和稀土基无机荧光粉组成的光泵浦LED，其实用性、能量和成本效益有限。电驱动WLED是解决光泵浦WLED的环境和效率问题的理想选择。然而，无论是基于传统的无机半导体还是基于有机半导体的电驱动WLED，仍然面临着材料制备和器件制造成本高、涉及高温和高真空工艺的严重问题和挑战。在这个项目中，FSU的Ma教授领导的研究团队旨在开发基于包含可溶液处理的卤化物钙钛矿和钙钛矿相关杂化材料的单一发光层的高性能电驱动WLED。该项目将为一类新兴的混合光电子材料产生材料化学、化学工程和器件物理方面的新知识。随着解决电驱动LED领域的主要挑战之一，即基于溶液可加工材料生产低成本高性能WLED，该项目的成功将对光电设备产生重大技术影响，有可能给全彩色显示器和固态照明行业带来革命性的变化。该项目还将教育和培训研究生和本科生在材料和设备方面的多学科研究，并通过各种社区外联活动促进STEM教育。卤化物钙钛矿及其相关杂化材料具有优异的光学和电学性能，使其在光伏电池、LED、激光器和光电探测器等各种光电子器件中得到了极大的应用。近年来，电驱动单色LED的开发取得了显著进展，发光范围覆盖了蓝到绿、红和近红外区。除了离域自由激子具有高色纯的窄发射外，许多卤化物钙钛矿和钙钛矿相关的有机金属卤化物杂化材料也被发现具有高效的宽带白光发射，其贡献来自自陷态激子。虽然已经实现了高效的光致发光，但使用这些材料获得高效的电驱动WLED或从自陷态激子中获得电致发光是具有挑战性的，部分原因是它们较差的电荷传输特性。利用卤化物钙钛矿和钙钛矿相关混合材料的特殊结构多样性，该项目旨在开发具有高电荷传输性能的新型白色发射材料系统，用于电驱动单发光层WLED，其性能可与现有WLED相媲美。更具体地说，该项目将(I)通过结构和组成的分子工程开发高效的白色发光卤化物钙钛矿和与钙钛矿相关的有机金属卤化物杂化材料；(Ii)研究制备具有可控形态和电子性能的白色发光薄膜的各种工艺方法；(Iii)通过适当的器件工程将白色发光薄膜与适当的电子和空穴传输层集成在一起，用于高效电驱动WLED；以及(Iv)建立新的白色发射材料和设备的工艺-结构-性能-性能关联。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。

White light emitting diodes (WLEDs) have changed the world over the last decades with wide applications in full color displays and solid state lighting. However, most practical WLEDs are optically pumped ones consisting of blue LED (e.g. InGaN) chips and rare-earth based inorganic phosphors with limited utility, energy, and cost efficiencies. Electrically driven WLEDs are highly desirable to resolve the environmental and efficiency issues of optically pumped WLEDs. However, electrically driven WLEDs based on either conventional inorganic semiconductors or organic semiconductors still face serious issues and challenges with high costs in both materials preparation and device manufacturing involving high temperature and high vacuum processes. In this project, the research team led by Prof. Ma at FSU aims to develop high performance electrically driven WLEDs based on single emissive layers containing solution processable halide perovskites and perovskite-related hybrid materials. This project will generate new knowledge in materials chemistry, chemical engineering, and device physics for an emerging class of hybrid optoelectronic materials. With addressing one of the major challenges in the field of electrically driven LEDs, that is producing low-cost high performance WLEDs based on solution processable materials, the success of this project will have significant technological impacts on optoelectronic devices with the potential to revolutionize the full color display and solid-state lighting industries. This project will also educate and train graduate and undergraduate students in multidisciplinary research in materials and devices, and promote STEM education through a variety of community outreach activities. Technical Description.The excellent optical and electronic properties of halide perovskites and perovskite-related hybrid materials make them of great interest for applications in a variety of optoelectronic devices, including photovoltaic cells (PVs), LEDs, lasers, and photodetectors. Recently, remarkable progress has been achieved in the development of electrically driven monochromatic LEDs with emissions covering blue to green, red, and near-infrared regions. Besides narrow emissions with high color purity from delocalized free excitons, many halide perovskites and perovskite-related organic metal halide hybrids have been discovered to exhibit highly efficient broadband white emissions with contributions from self-trapped excitons. While efficient photoluminescence has been achieved, obtaining efficient electrically driven WLEDs or electroluminescence from self-trapped excitons using these materials is challenging, partially due to their poor charge transport properties. Taking advantage of the exceptional structural versatility of halide perovskites and perovskite-related hybrid materials, this project aims to develop new white emitting material systems with high charge transport properties for electrically driven single emissive layer based WLEDs with performance comparable to existing WLEDs. More specifically, this project will (i) develop highly efficient white light emitting halide perovskites and perovskite-related organic metal halide hybrids by molecular engineering of the structures and compositions; (ii) investigate various processing approaches for the preparation of white emitting thin films with controlled morphological and electronic properties; (iii) integrate white light emitting thin films with appropriate electron and hole transporting layers though appropriate device engineering for highly efficient electrically driven WLEDs; and (iv) establish the processing-structure-property-performance correlations for the new white emitting materials and 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.