Solution-processed nanocrystal optoelectronics: from colloidal quantum dots to wells for lighting and lasing

Solution-processed nanocrystal optoelectronics: from colloidal quantum dots to wells for lighting and lasing
Thursday, January 8, 2015 - 4:15pm to 5:15pm
Spilker 232
Prof. Hilmi Volkan Demir (Bilkent University, Turkey, and LUMINOUS! NTU Singapore)
Abstract / Description: 

Solution-processed semiconductor nanocrystals have attracted great interest in optoelectronics including color conversion and enrichment in quality lighting and display backlighting [1]. In this talk, we will present types of colloidal nanocrystals obtained by tailoring and controlling the composition, size, and dimensionality of these semiconductor nanomaterials in an effort to realize high performance in light generation and lasing [2]. Based on rational designs and control of the excitonic properties in these nanocrystals, we successfully demonstrated efficient light-emitting diodes [3] and lasers [4-5]. These include colloidal quantum dots, quantum rods and quantum wells. We showed that electronic-type tuning in colloidal quantum dots and rods allows for the fine tunability of the spectral position of the amplified spontaneous emission [4]. Ultra-low threshold stimulated emission in the blue to red was achieved using engineered core/shell quantum dots enabling suppressed Auger recombination. We developed an all-colloidal laser using the nanocrystals as optical gain media. Also, we showed that the colloidal quantum wells uniquely combine ultra-low threshold stimulated emission and record high optical gain coefficients; and the excitonic properties of these colloidal quantum wells can further be tuned by controlled stacking [5]. Furthermore, we developed large-area (> 50 ? 50 cm) freestanding sheets of nanocrystals and their integrated macrocrystals towards stable, efficient and quality solid-state lighting [6]. These results indicate that colloidal optoelectronics holds great promise to challenge epitaxial counterparts in the near future.

[1] H. V. Demir et al., Nano Today 6, 632 (2011); T. Erdem and H. V. Demir, Nature Photonics 5, 126 (2011).
[2] B. Guzelturk et al. Laser & Photonics Reviews 8, 73 (2014); and J. Phys. Chem. Lett. 5, 2214 (2014).
[3] X. Yang et al., Advanced Materials 24, 4180 (2012); Advanced Functional Materials 24, 5977 (2014); ACS Nano 8, 8224 (2014); and Small 10, 246 (2014).
[4] A. F. Cihan et al. ACS Nano 7, 4799 (2013); and J. Phys. Chem. Lett. 4, 4146 (2013).
[5] B. Guzelturk et al. ACS Nano 8, 6599 (2014); and ACS Nano (2014). DOI: 10.1021/nn5053734.
[6] E. Mutlugun et al., Nano Letters 12, 3986 (2012); and T. Otto et al., Nano Letters 12, 5348 (2012).

This seminar is sponsored by Stanford OSA.

Dr. Hilmi Volkan Demir is an alumnus of Ginzton Lab and Stanford Photonics Research Center. He is currently EURYI Associate Professor at Bilkent University and UNAM ? National Nanotechnology Research Center of Turkey. Concurrently, he is an NRF Fellow of Singapore and Nanyang Associate Professor at NTU Singapore, and serves as the Founding Director of LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays. Demir earned his PhD (2004) and MSc (2000) degrees in electrical engineering from Stanford University, CA, and his BSc (1998) degree in electrical and electronics engineering from Bilkent University (one of the top ranking science and engineering schools in Turkey). His current research interests include the science and technology of semiconductor lighting; nanocrystal optoelectronics; excitonics and plasmonics for high-efficiency light generation and harvesting; and wireless in vivo sensing and smart implants for future healthcare. Demir published over 150 peer-reviewed research articles in major scientific journals and delivered over 150 invited seminars and lectures on the topics of LED lighting, nanophotonics, in vivo sensing, and nanoparticles research in industry and academia. Demir has contributed to commercialization and licensing of several new enabling technologies as well as establishing two successful companies and led to >30 patent applications (granted and pending), several of which have currently been used, owned or licensed by the industry. These scientific and entrepreneurship activities resulted in several important international and national awards including Nanyang Award for Research Excellence, European Science Foundation European Young Investigator Award, TUBITAK Scientific and Technological Research Council of Turkey Young Investigator TESVIK Award, and TUBA-GEBIP Distinguished Young Scientist Award. He has been selected The Outstanding Young Person in the World (TOYP Award) of Junior Chamber International (JCI) Federation of Young Leaders and Entrepreneurs Worldwide in the category of academic achievement and leadership. He is the PI of Singapore NRF Competitive Research Program on future lighting using excitonics. He is the SPRINGER-VERLAG Series Editor of Nanoscience and Nanotechnology and an OSA editor of Optics Express. He is a selected partner of European Union FP7 Nanophotonics for Energy Network of Excellence (N4E NoE) and an elected Associate Member of the Turkish National Academy of Sciences.