GLOBAL-Promoting Research Partnership in Fabrication of Advanced III-nitride Optoelectronics With Ultra Energy Efficiency Using Nanotechnology

我们的研究有可能应对人类面临的两大挑战：能源危机和气候变化。目前，由于普通照明而消耗的能源占世界总能源消耗的29%。虽然地球上一小时的太阳辐射提供的能量相当于全球每年的总能耗，但太阳能电池对这一数字的贡献仅为0.03%。因此，有必要开发新技术来实现超高能效的固态照明光源和太阳能电池。III-氮化物半导体的出现为人类提供了这样一个独特的机会，因为III-氮化物的光发射覆盖了整个可见光光谱，也覆盖了太阳光谱的主要部分。据预测，如果在我们的家庭和办公室使用III-氮化物LED，可以节省15%的发电站发电量，15%的燃料消耗，并减少15%的碳排放。十多年来，全球一直致力于开发高亮度的III-氮化物LED(HB-LED)。因此，取得了重大成就。然而，一个致命的问题已经出现，迫切需要解决。这就是众所周知的“效率下降”：HB-LED的效率只有在低注入电流时才显示出最高值，而注入电流的进一步增加会导致效率显著降低。这就是“效率下降”。在实际应用所需的注入电流下，效率下降到峰值的50%，这意味着浪费了大量的能量。这还会导致严重的可靠性问题，因为浪费的能量会导致设备温度升高，从而严重降低设备性能。效率下降的物理根源非常复杂，因此不清楚。到目前为止，还没有任何有效的解决方案。在该项目中，来自谢菲尔德大学、美国耶鲁大学、南京大学(中国)和德国布伦斯韦格科技大学的6个世界领先团队的科学家汇集了他们独特而互补的专业知识，提议采用多项先进的纳米技术和外延生长技术来探索根本问题，然后实现超高能效LED。对于太阳能电池，据预测，使用III-氮化物可以达到&gt；50%的能量转换效率，远远高于任何现有的太阳能电池。由于一些技术挑战，目前III-氮化物太阳能电池的太阳能转换效率极低，在最好的报告中只有3%左右。我们将结合来自6个团队的互补专业知识，通过采用类似的纳米技术，在具有超高晶体质量的GaN衬底上具有厚超晶格结构的外延片上制备纳米棒阵列太阳能电池，以应对挑战。

Our research has the potential to meet two major challenges which human beings are facing: energy crisis and climate change. Currently, the energy consumed due to general illumination accounts for 29% of the world's total energy consumption. Although the energy provided by an hour of solar radiation on the Earth is equivalent to the world's total energy consumption per year, solar cells contribute only 0.03% to the figure. Therefore, it is necessary to develop new technologies to achieve ultra energy-efficient solid-state lighting sources and solar cells. The appearance of III-nitride semiconductors provides human beings with such a unique opportunity, as the light emission from III-nitrides covers the complete visible spectrum and also a major part of the solar spectrum. It has been predicted that III-nitride LEDs if used in our homes and offices could save 15% of the electricity generated at power stations, 15% of the fuel used, and 15% reduction in carbon emission.For more than a decade substantial efforts have been devoted to developing high-brightness III-nitride LEDs (HB-LEDs) worldwide. Consequently, major achievements have been made. However, a fatal problem has appeared, and has to be solved urgently. That is the well-known "efficiency droop": the efficiency of HB-LEDs shows the highest value only at a low injection current, and a further increase in injection current leads to a significant reduction in efficiency. This is the "efficiency droop". Under the injection current required for practical applications, the efficiency drops down to >50% of the peak value, meaning that a large amount of energy has been wasted. This also causes a severe reliability issue, as the wasted energy leads to an elevated temperature of the devices and thus severe degradation in device performance. The physical origins of the efficiency droop are very complicated and thus unclear. So far, there is not any efficient solution. In the project, the scientists from 6 world-leading teams at University of Sheffield, Yale University (USA), Nanjing University (China) and Technology University of Braunschweig (Germany) are pooling their unique but complementary expertise, proposing to employ a number of advanced nanotechnologies and epitaxial growth techniques in order to explore the fundamental issue, and then achieve ultra energy-efficient LEDs. For solar cells, it has been predicted that an energy-conversion efficiency of >50% can be achieved with III-nitrides, which is much higher than that of any current solar cell. The solar energy-conversion efficiency of current III-nitride solar cells is extremely low, only ~3% in the best report due to a number of technologic challenges. We will combine our complementary expertise from 6 teams to tackle the challenges by employing a similar nanotechnology to fabricate into nanorod array solar cells on the epiwafers with a thick super-lattice structure on the GaN substrates with ultra-high crystal quality.