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Nanocrystal optoelectronics: from solution-processed quantum dots to wells

Speaker: 
Hilmi Volkan Demir (CA2DM & Luminous, NTU)
Date: 
Wed, 12/08/2015 - 11:00am to 12:00pm
Location: 
New Physics Conference Room (S11-02-07)
Event Type: 
Seminars

Abstract

Solution-processed semiconductor nanocrystals have attracted great interest in photonics including color conversion and enrichment in quality lighting and display backlighting [1]. In this talk, we will present architectures of colloidal nanocrystals obtained by tailoring and controlling the dimensionality, size, and composition of these nanostructures in an effort to realize high performance in light generation and lasing [2]. These cover types of colloidal quantum dots, quantum rods and quantum wells. Based on the rational design and control of excitonic processes in these nanocrystals, we successfully demonstrated highly efficient light- emitting diodes [3] and lasers [4,5]. To this end, we systematically studied and showed that electronic-type tuning in colloidal quantum heterostructures allows for fine tunability [6]. Here ultra-low threshold stimulated emission was achieved using engineered core/shell architectures enabling substantially suppressed Auger recombination, enabling the first liquid laser of nanocrystals [4]. Also, we developed an all-colloidal solid laser using these nanocrystals as the optical gain media for the first time in a fully colloidal resonator [5]. As an extreme case of solution-processed highly-confined quasi-2D colloids, we showed that the atomically flat heteronanoplatelets uniquely combine ultra-low threshold stimulated emission and record high optical gain coefficients and the controlled stacking of these nanoplatelets further tune their excitonic properties [7]. The recent progress in the colloidal optoelectronics suggest that solution-processed quantum materials hold great promise to challenge epitaxial counterparts in the near future.

References:

[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] Y. Wang et al., Advanced Materials 27, 169 (2015).
[5] B. Guzelturk et al., Advanced Materials in press (2015). DOI: 10.1002/adma.201500418
[6] A. F. Cihan et al. ACS Nano 7, 4799 (2013); and J. Phys. Chem. Lett. 4, 4146 (2013).
[7] B. Guzelturk et al. ACS Nano 8, 6599 (2014); and ACS Nano 8, 12524 (2014).

Speaker's bio

Dr. Hilmi Volkan Demir is a professor of electrical engineering and physics. He is an NRF Fellow of Singapore, and serves as the Founding Director of LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays at NTU Singapore. 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 200 peer-reviewed research articles in major scientific journals and delivered over 150 invited seminars, lectures and colloquia 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, ESF 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 will serve as the Technical Chair (Washington DC 2015), Member-at-Large (Hawaii 2016), and General Chair (2017) of the IEEE Photonics Society’s flagship program IEEE Photonics Conference (IPC). 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.

 

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