Electrically Driven Single Emissive Layer Based White Light Emitting Diodes

白色发光二极管（WLED）在过去的几十年中已经改变了世界，其在全彩色显示器和固态照明中的广泛应用。然而，大多数实际的WLED是由蓝色LED（例如InGaN）芯片和稀土基无机磷光体组成的光泵浦的WLED，其具有有限的效用、能量和成本效率。电驱动的WLED对于解决光泵浦WLED的环境和效率问题是非常期望的。然而，基于常规无机半导体或有机半导体的电驱动WLED在涉及高温和高真空工艺的材料制备和器件制造中仍然面临严重的问题和高成本的挑战。在该项目中，由FSU的Ma教授领导的研究团队旨在开发基于单一发光层的高性能电驱动WLED，该发光层包含可溶液加工的卤化物钙钛矿和钙钛矿相关的混合材料。该项目将为新兴的混合光电材料类产生材料化学，化学工程和器件物理学方面的新知识。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器件产生重大技术影响，并有可能彻底改变全彩色显示器和固态照明行业。该项目还将教育和培训研究生和本科生进行材料和设备的多学科研究，并通过各种社区外展活动促进STEM教育。技术描述：卤化物钙钛矿和钙钛矿相关的混合材料的优异的光学和电子性质使它们在各种光电器件中的应用引起极大兴趣，包括光伏电池（PV）、LED、激光器和光电探测器。最近，在电驱动单色LED的开发中已经取得了显著的进展，其发射覆盖蓝色到绿色、红色和近红外区域。除了来自离域自由激子的具有高色纯度的窄发射之外，已经发现许多卤化物钙钛矿和钙钛矿相关的有机金属卤化物混合物表现出具有来自自陷激子的贡献的高效宽带白色发射。虽然已经实现了有效的光致发光，但是使用这些材料从自陷激子获得有效的电驱动WLED或电致发光是具有挑战性的，部分原因是它们的电荷传输特性差。利用卤化物钙钛矿和钙钛矿相关杂化材料的特殊结构多功能性，该项目旨在开发具有高电荷传输性能的新型白色发光材料系统，用于电驱动的基于单发光层的WLED，其性能与现有的WLED相当。更具体地说，本项目将（i）通过结构和组成的分子工程开发高效的白色发光的卤化物钙钛矿和与钙钛矿相关的有机金属卤化物杂化物;（ii）研究制备具有可控形态和电子特性的白色发光薄膜的各种加工方法;（iii）通过用于高效电驱动WLED的适当器件工程，将白色发光薄膜与适当的电子和空穴传输层集成;以及（iv）为新的白色发光材料和器件建立工艺-结构-性能-性能的相关性。该奖项反映了NSF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。

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.