NP2: Hybrid Nanoparticle-Nanoporous nitride materials as a novel precision manufacture route to optoelectronic devices

增强现实（AR）具有将数字世界与物理现实无缝集成的能力。它可以为外科医生提供重要的医疗数据，允许运动员在运动时无缝访问训练信息，并在商业、休闲等领域提供无数其他机会。然而，目前的AR技术受到微显示器性能的影响。增强现实设备不仅要能在黑暗的房间里成功运行，还要能在明亮的阳光下成功运行，而且必须非常小，用紧凑型电池一次充电就能运行一整天。因此，就亮度和效率而言，对微型显示器中的微小光源提出了巨大的要求。为了使增强现实成为一种大众市场技术，任何新的微显示器方法都不仅需要满足这些需求，还需要易于制造。目前的发光二极管（led）无法满足这些需求，因为当器件尺寸缩小以满足AR施加的外形尺寸和分辨率要求时，适用于更大面积光源的关键材料的效率会下降。然而，就大规模led而言，基于氮化镓（GaN）的器件取得了巨大的成功，改变了照明行业。氮化镓发光二极管也显示出更低的效率下降与缩小尺寸比其他类似材料。不幸的是，这些GaN led仅对光谱蓝色区域的光发射高效。基于相同材料的绿色、琥珀色，尤其是红色器件的效率要低得多，但要制造全彩微型显示器却必须如此。在白光LED灯泡中，蓝光通过荧光粉材料转换成其他颜色，但这些荧光粉被制造成体积庞大的微米级粉末，太粗糙，无法用于微型LED。在这个项目中，我们将采用一种新的方法，将替代的纳米级荧光粉颗粒（大约100个原子宽）与氮化led集成在一起。我们的替代荧光粉是高度发光的胶体纳米粒子，使用可扩展的技术直接在溶液中合成，很容易制成纳米颗粒油墨。这些材料已经用于“QLED”显示技术，但显示器制造很复杂，随着设备的缩小，难度大大增加。我们的新概念是使用印刷技术将纳米颗粒注入GaN本身的纳米级孔中，而不是注入led表面。纳米多孔氮化镓材料是最近的一项发展，我们的实验室发明了独特的、可扩展的制造方法。通过在这些多孔支架上打印，我们将利用毛细管作用将纳米颗粒吸入设备的所需区域，防止纳米颗粒油墨的扩散，从而实现所需规模的直接控制制造。这样，我们将创造一种新的光学复合材料-氮化镓和高度发光纳米颗粒的组合-通过使用纳米孔的结构来排列和控制纳米颗粒阵列，我们将启用新的和更复杂的设备，用于未来的显示技术，如三维增强现实。

Augmented reality (AR) has the power to seamlessly integrate the digital world with physical reality. It could provide surgeons with vital medical data as they operate, allow athletes to access training information seamlessly whilst playing sports and offers countless other opportunities in business, leisure and beyond. However, currently AR technologies are let down by the performance of microdisplays. AR devices must operate successfully not only in darkened rooms but also in bright sunlight, and must also be very small and run all day on one charge of a compact battery. Hence, enormous demands are placed on tiny light emitters in microdisplays in terms of brightness and efficiency. For AR to become a mass market technology, any new approach to microdisplays will need to not only meet these demands, but also allow easy manufacturing.Current light emitting diodes (LEDs) fail to meet these needs, since key materials which work well for larger area light emitters exhibit a drop in efficiency when the device size is shrunk to meet the demands of form factor and resolution imposed by AR. However, in terms of large scale LEDs, devices based on gallium nitride (GaN) have been tremendously successful, transforming the lighting industry. GaN LEDs also show much lower drops in efficiency with reduction in size than other similar materials. Unfortunately, these GaN LEDs are highly efficient only for light emission in the blue region of the spectrum. Green, amber and particularly red devices based on the same materials have much lower efficiencies, but are needed to create full colour microdisplays. In white LED light bulbs, blue light is converted to other colours by phosphor materials, but these phosphors are manufactured as bulky micron sized powders, too coarse to be used in microLEDs.In this project, we will take a new approach to integrating alternative, nanometre-scale phosphor particles (ca. 100 atoms wide) with nitride LEDs. Our alternative phosphors are highly luminescent colloidal nanoparticles, synthesised straightforwardly in solution using scalable techniques and easily made into nanoparticle inks. These materials are already used in "QLED" display technologies, but display manufacture is complex and the difficulties increase substantially as the device shrinks. Our new concept is to use printing technologies to inject nanoparticles not onto the surface of LEDs, but into nanoscale pores in the GaN itself. The nanoporous GaN materials are a very recent development and unique, scalable methods for their fabrication have been invented in our laboratory. By printing onto these porous scaffolds we will exploit capillary action to suck the nanoparticles into the desired region of the device, preventing spreading of the nanoparticle ink and hence achieving controlled manufacture straightforwardly at the required scale. In so doing, we will create a new optical composite material - a combination of the GaN and the highly luminescent nanoparticles - and by using the structure of the nanopores to align and control the array of nanoparticles, we will enable new and more sophisticated devices, for future display technologies such as AR in three dimensions.