Blue-emitting Phosphors for Solid State Lighting Applications

内容：人造照明的发明可以追溯到约瑟夫·威尔逊·斯旺和托马斯·爱迪生在1879年对白炽灯泡的发明和商业化的开创性贡献，可以说是人类最重要的发明之一。人工照明使大多数人类活动能够在日落后继续进行，从而不可估量地提高了全世界的人类生产力。虽然爱迪生的装置比蜡烛照明亮得多，但效率很低，只能将0.2%的电力转化为光。自从这个开创性的发明以来，已经开发了许多其他照明设备，从钨丝灯到荧光灯管到卤素照明到发光二极管（LED）到有机发光二极管（OLED）。随着照明技术的每一次进一步迭代，该设备产生的光的质量（颜色的纯度）、功率效率和亮度都有所提高。光的发射还可以使信息显示器、电视机和电脑屏幕成为可能。生产节能的设备尤为重要，因为据美国能源部估计，仅在美国，就有1/3的商业用电和10%的家庭用电用于人工照明。人工照明仅在美国就代表了150亿美元的市场，在全球范围内几乎达到910亿美元，相当于全球能源总产量的20%。与这种能源消耗相关的环境影响是巨大的，估计占全球二氧化碳排放量的7%。虽然无机LED和有机或聚合物OLED照明现在是人工照明的最新技术，但它们的高成本和小的有效表面积仍然是广泛采用的障碍。事实上，对于大表面积的户外照明应用，低压钠灯仍然是首选的技术。在此背景下，迫切需要找到替代的人工照明技术，其具有更低的生产成本、更高的能效、颜色可调，并且可以用于当前LED和OLED技术目前无法访问的环境中。这意味着，以类似于OLED的方式，这种新的照明技术将在视觉显示器、电信和传感器中得到应用。能够利用光和/或电流并将这种能量转化为有用的功的有机复合物是许多重要应用的核心。我的研究小组特别感兴趣的一个应用是基于磷光发光电化学电池（LEEC）架构或OLED架构的节能视觉显示器和平板照明。目前，大多数基于离子过渡金属络合物（iTMC）的LEEC依赖于使用带电铱（III）络合物作为发光材料。这些络合物可以容易地进行溶液处理。铱络合物发磷光，因此理论上可达到的最大光致发光量子效率（PLQY）为1。已经发现LEEC器件的外部量子效率（EQE）与固态PLQY成比例地缩放，并且因此明亮的器件是可能的。尽管具有上述优点，但包含iTMC的LEEC具有几个缺点：（i）低EQE;（ii）器件的有限稳定性和（iv）颜色质量，特别是关于蓝光发射。两个主要目标是：1。以获得在光谱的蓝色区域中明亮地发射并且在数千小时内稳定并且在施加外部电压时可以快速发光的LEEC;以产生更高性能的深蓝色发射OLED。

Context: The invention of artificial lighting, dating from Joseph Wilson Swan and Thomas Edison's seminal contributions to the invention and commercialization of the incandescent light bulb in 1879, is arguably one of the most important inventions of humankind. Artificial lighting permits most human activities to continue past sundown, thus immeasurably increasing worldwide human productivity. Though Edison's device was much brighter than candle lighting, it was inefficient, converting only 0.2% of electricity into light. Since this seminal invention, many other lighting devices have been developed, from the tungsten lamp, to fluorescent tubes to halogen lighting to light-emitting diodes (LEDs) to organic light-emitting diodes (OLEDs). With each further iteration in lighting technology, the quality (pureness of colour), power efficiency and brightness of the light produced by the device have each improved. Light emission also enables information displays, televisions and computer screens.Producing devices that are energy efficient is of particular importance as, according to the US Department of Energy, it is estimated that 1/3 of commercial electricity use and 10% of household electricity consumption in the United States alone is dedicated towards artificial lighting. Artificial lighting represents a $15 Billion market in the United States alone and almost $91 Billion worldwide, corresponding to 20% of total worldwide energy output. The environmental impact related to this energy consumption is enormous and is estimated to be responsible for 7% of global CO2 emissions. Whereas inorganic LED and organic or polymer OLED lighting is now the state of the art in artificial lighting, their high cost and small active surface area are still barriers to wide adoption. In fact, for large surface area outdoor lighting applications, low-pressure sodium lamps are still the technology of first choice. Within this context, there is an urgent need to find alternative artificial lighting technologies that are of lower production cost, more energy efficient, colour tunable and can be used in environments not currently accessible to current LED and OLED technologies. It is implicit that in a similar manner to OLEDs, such a new lighting technology would have applications in visual displays, telecommunication and sensors.Organometallic complexes capable of harnessing light and/or electrical current and transforming such energy into useful work are at the heart of many important applications. An application that is of particular interest to my research group is energy-efficient visual displays and flat panel lighting based on either a phosphorescent light-emitting electrochemical cell (LEEC) architecture or an OLED architecture. Currently, most ionic transition metal complex-based (iTMC) LEECs rely on the use of a charged iridium(III) complex as the luminophoric material. These complexes can be readily solution processed. Iridium complexes phosphoresce and thus the maximum photoluminescence quantum efficiency (PLQY) theoretically attainable is unity. The external quantum efficiency (EQE) of a LEEC device has been found to scale proportionately to the solid-state PLQY and as such bright devices are possible. Despite the advantages listed above, LEECs incorporating iTMCs have several weaknesses: (i) low EQE; (ii) limited stability of the device and (iv) colour quality, particularly with reference to blue light emission.This grant proposal targets the development blue-emitting iridium(III) cationic complexes that will act as a luminophoric material in both LEEC and OLED devices. The two main goals are: 1. to obtain a LEEC that emits brightly in the blue region of the spectrum and that is stable over thousands of hours and that can quickly illuminate upon the application of an external voltage; to produce higher performance deep blue emitting OLEDs.