Optics & Electronics seminar: Semiconductor Nanocrystal Optoelectronics: A Journey from Colloidal Quantum Dots to Wells

[AP483] Semiconductor Nanocrystal Optoelectronics: A Journey from Colloidal Quantum Dots to Wells
Monday, April 12, 2021 - 12:00pm
Prof. Hilmi Volkan Demir (Bilkent Univ/NTU)
Abstract / Description: 

Semiconductor nanocrystals have attracted great interest for color conversion and enrichment in quality lighting and displays. Optical properties of these solution‑processed nanostructures are conveniently controlled by tailoring their size, shape, and composition in an effort to realize high‑performance light generation and lasing. These colloids span different types and heterostructures of semiconductors in the forms of quantum dots and rods to the latest sub‑family of nanocrystals, the colloidal quantum wells (CQWs). In this talk, we will introduce the emerging field of semiconductor nanocrystal optoelectronics, with most recent examples of their photonic structures and optoelectronic devices employing such atomically‑flat, tightly‑confined, quasi‑two‑dimensional CQWs, also popularly nick-named 'nanoplatelets'. Among their various extraordinary features, we will show that these CQWs enable record high optical gain coefficients [1] and can achieve gain thresholds at the level of sub‑single exciton population per CQW on average [2], empowered by carefully engineering their heterostructure [3]. Next, we will present a new, powerful, large-area self‑assembly tool for orientation controlling of these nanoplatelets [4], which provides us with the ability to tune and master their excitonic properties in their ensemble, as well as the level of achievable energy transfer among them and with other nearby species. Using three‑dimensional constructs of face‑down self‑assembled slabs of CQWs with monolayer precision, we will demonstrate ultrathin optical gain media and lasers of these oriented CQW assemblies [5]. Finally, we will show record high‑efficiency colloidal LEDs using CQWs employed as the electrically‑driven active emitter layer [6] and record low-threshold solution lasers using the same CQWs employed as the optically‑pumped fluidic gain medium [7]. Given their current accelerating progress, these solution‑processed quantum well materials hold great promise to challenge their epitaxial thin‑film counterparts in semiconductor optoelectronics in the near future.

[1] B. Guzelturk et al., HVD, Nano Letters 19, 277 (2019)
[2] N. Taghipour et al., HVD, Nature Comm 11, 3305 (2020)
[3] Y. Altıntas et al., HVD, ACS Nano 13, 10662 (2019)
[4] O. Erdem et al., HVD, Nano Letters 19, 4297 (2019)
[5] O. Erdem et al., HVD, Nano Letters 20, 6459 (2020)
[6] B. Liu et al., HVD, Advanced Materials 32, 1905824 (2020)
[7] J. Maskoun et al., HVD, Advanced Materials (2021), in print, DOI:(10.1002/adma.202007131)

Spring 2021 speakers organized by Prof. David A.B. Miller

Bio: Dr. Demir is a professor of electrical engineering, physics, and materials science. He is an NRF Fellow of Singapore and is the Founding Director of LUMINOUS! Centre of Excellence for Semiconductor Lighting and Displays at NTU Singapore – Nanyang Technological University. Concurrently, he is the European Science Foundation EURYI Professor of Bilkent University, Ankara (his alma mater), and Director of UNAM – National Nanotechnology Research Center of Turkey (under MoU with NTU). 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 (a top-ranking science and engineering school in Turkey). His current research interests include the science and technology of semiconductor lighting, nanocrystal optoelectronics, and smart implants. Demir published over 350 peer-reviewed research articles in major scientific journals and delivered over 200 invited seminars, lectures and colloquia on the topics of LED lighting, colloidal nanophotonics, in vivo sensing, and nanoparticles research in industry and academia. Demir has contributed to the commercialization and licensing of over 10 new enabling technologies, as well as establishing 4 successful companies, which led to >130 patent applications (granted and pending) as Principal Inventor. These scientific and entrepreneurship activities resulted in several important awards, including the Nanyang Award for Research Excellence, the NRF Investigator Award of Singapore, the Science Award of The Scientific and Technological Research Council of Turkey (TUBITAK), and the Turkish National Academy of Sciences Distinguished Young Scientist Award. He is an elected Fellow of IEEE and OSA and is a (full) Member of the Turkish National Academy of Sciences.