Wednesday, March 14, 2013, 1:00 p.m.
Dolan E133, Physics Department
Prof. Hongping Zhao
Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH 44106, USA
￼Energy efficiency and renewable energy technologies have significant importance for achieving sustainable energy systems in modern society. Lighting accounts for more than 22% of the total electrical energy usage in US, and technologies based on solid state lighting (SSL) utilizing semiconductor-based material has tremendous promise to replace the existing lighting devices. As compared to traditional incandescent and fluorescent lamps, SSL is more energy-efficient, reliable, and environmentally-friendly. Once widely used, SSL could lead to the decrease of worldwide electricity consumption for lighting by >50% and reduces total electricity consumption by >10%. The U.S. Department of Energy describes SSL as a pivotal emerging technology that promises to fundamentally alter lighting in the future. Rapid progress in SSL research and development has resulted in the advent of light emitting diodes (LEDs) for general lighting applications. Three major challenges for current state-of-art III-nitride based LEDs are 1) ‘green gap’ issue in InGaN quantum well light-emitting diodes, 2) ‘efficiency droop’ issue in III-nitride LEDs resulting in output power quenching at high current injection, and 3) limited light extraction efficiency in InGaN QWs LEDs.
In this talk, I will discuss our novel approaches to address the major issues related to state-of-the-art nitride LEDs, in particular related to 1) engineering of InGaN nanostructure active layers for achieving high internal quantum efficiency and minimal efficiency droop in nitride LEDs, 2) the use of surface plasmon approach for increasing the radiative efficiency in nitride LEDs, and 3) microdome structures for enhancing LED light extraction efficiency.
Short Biography for Prof. Hongping Zhao:
Dr. Hongping Zhao is an assistant professor in the Department of Electrical Engineering and Computer Science (EECS) at Case Western Reserve University, since July 2011. She received her PhD in Electrical Engineering from Lehigh University in Jan. 2011. She is a recipient of the Rossin Doctoral Fellowship and Sherman Fairchild Fellowship at Lehigh, as well as the 2008 and 2009 SPIE Educational Scholarship. Her research works encompass interdisciplinary areas of nanostructure, semiconductor devices, and energy-based device technology. Her research areas cover simulation, device physics, epitaxy, and fabrication of III-nitride semiconductor photonics and nanostructure devices for energy-efficiency and renewable energy technologies. Her research interests include novel III-nitride photonics and electronics devices for solid state lighting, laser diodes and solar cells. Dr. Zhao has published more than 35 refereed journal and 73 refereed conference papers. Dr. Zhao also serves as an editorial board member of the journal Optics.