基于低维钙钛矿A位有机胺位阻效应的激子调控及其白光电致发光研究

With the arrival of big data and artificial intelligence era, low dimensional perovskite materials have been a hot field in the semiconductor optoelectronics for the new requirements of flexibility, wearables, intelligent sensing in the white display and lighting industry, due to their advantages of outstanding film-forming performance, flexible, and adjustable spectral range. However, the white fluorescence efficiency of the low dimensional perovskite is low at the room temperature, and this weakness is the bottleneck of the low dimensional perovskite in the white lighting flexible displays. This project proposes to investigate physical mechanism of the enhanced high-efficiency white emission at room temperature through studying the structure-function relationship between exciton energy bandgap and stereo-hindrance effect of A-site organoammonium in low dimensional organic-inorganic hybrid perovskites. The A-site organoammonium components in low-dimensional perovskites will be systematically adjusted and the stereo-hindrance effect will induce the modification of the crystal structure and the energy band gap, promoting the localization effect of the bound excitons. These changes will modify the color range of emission spectra and improve the fluorescence quantum efficiency of exciton emission at room temperature. Based on the exploration of energy transfer process between the free excitons and self-trapped excitons and the exciton-phonon coupling interaction, we propose the possible physical mechanism of modulating the enhanced room-temperature exciton luminescence by A-site organic amine component adjustment. In the other hand, we investigate the device interface relationship between the A-site organoammonium cations of the luminescent layer and the materials in other functional layers and their influence on carrier migration. By improving the carrier recombination efficiency, we hope to obtain the efficient white electroluminescent device at room temperature and promote the development of perovskite-based LED in white light display and lighting.

随着大数据人工智能时代的到来，面向白光显示照明行业柔性化、可穿戴、智能传感等方面的新要求，低维钙钛矿材料由于具有成膜性能好、可柔性化、光谱可调等优势，成为半导体光电领域的研究热点，但尚存在室温白光荧光效率不高的问题，成为低维钙钛矿白光柔性显示的瓶颈。本项目拟通过研究A位有机胺空间位阻效应与激子能带调控之间的构效关系来阐明室温白光荧光增强的物理机制。通过系统地调节低维钙钛矿A位有机胺组份，产生位阻效应引起晶体结构及能带的变化，促进激子的局域化效应增强，以此调控激子发射的光谱范围及提高室温激子发射荧光量子效率；基于自由激子和自陷激子的能量传递及激子-声子耦合效应分析，研究A位有机胺组分调制室温激子发光增强的机理；研究发光层A位有机胺种类与电致发光器件各功能层的界面及载流子迁移的关联性，提升载流子复合效率，获得室温高效白光电致发光器件，推进钙钛矿基LED在白光显示与照明领域的进一步发展。

有机-无机杂化低维钙钛矿材料因具有高发光效率、材料来源广泛、可溶液制备等优势而备受研究者关注，但其铅毒性隐患、较低的白光量子产率和较差的白光电致发光性能仍然限制其进一步发展。本项目通过系统研究低维钙钛矿A位有机胺的空间位阻效应，调控其光致发光和电致发光性能，成功开发了多种优异性能的低维钙钛矿和金属卤化物荧光材料。具体而言，我们实现了以下几项工作：1）制备了一种长链有机胺盐的环己烯胺溴化铅橙色发光材料，该研究对低温抗热猝灭荧光性能的研究具有启发和指导意义。2）制备了一种四甲基氟化铵六氟钛酸的窄带红光材料，该项工作突破了美国通用电气公司KSF:Mn4+全无机红光材料的专利保护，具有广泛的应用前景，特别是在暖白光照明和显示领域。3）开发了一系列基于具有大位阻空间特性的四苯基鏻（TPP+）金属卤化物材料。其中，四苯基鏻氟钛酸和四苯基鏻氟锆酸具有室温磷光特性，在紫外光激发下可保持长达6秒的磷光衰减，可用于制作防伪标签。四苯基鏻锑氯化物[TPP]2SbCl5是一种新型的橙色荧光材料，可用于电致发光，晶体具有90%以上的室温荧光量子产率。基于该材料制备的器件可以发射CIE坐标为（0.36，0.31）的暖白光。这项工作为自陷激子电致发光特性的研究提供了一个很好的范例。4）我们发展了一种亚铜基金属卤化物LED器件的制备技术，并通过多种表征证实，亚铜基金属卤化物的发光不是来源于自陷激子发光，而是器件界面原位形成的碘化亚铜基有机配合物的发光。这项工作的结果厘清了关于金属卤化物宽带电致发光的一些误解和争议，有利于推动无铅暖白光LED器件的进一步研发进程。