CeNS Colloquium

Prof. Hilmi Volkan Demir, Nanyang Technological University Singapore

Colloidal semiconductor nanocrystals have been attracting increasingly greater interest in photonics including color conversion and enrichment in quality lighting and display backlighting [1]. Optical properties of these nanocrystals can be conveniently tuned by controlling their underlying excitonic mechanisms [2]. Their rational design and excitonic control provide us with the ability to make highly efficient light-emitting diodes [3] and optically-pumped lasers [4]. In this talk, we will introduce the emerging field of nanocrystal optoelectronics using solution-processed quantum dots to wells. In particular, we will present a new concept of all-colloidal lasers developed by incorporating nanocrystal emitters as the optical gain media intimately into fully colloidal cavities [5]. As an extreme case of solution-processed tightly-confined quasi-2D quantum structures, we will also show that atomically flat nanocrystals, analog of epitaxial thin-film quantum wells, allow for record high optical gain and ultralow lasing threshold among all colloids. In addition, we will discuss that controlled stacking of these colloidal quantum wells uniquely enables us to fine-tune and master their excitonic properties [6]. We will also show that doping such nanoplatelets leads to extraordinarily large Stokes shift, accompanied with near-unity quantum efficiency and high absorption cross-section, ideal for luminescent solar concentrators [7]. Furthermore, advanced heterostructures of these nanoplatelets make it possible to target other applications such as remote temperature sensing [8]. Given the recent accelerating progress in nanocrystal optoelectronics, solution-processed quantum materials hold great promise to challenge their conventional epitaxial counterparts.

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[4] YWang et al. HVD and HSun, Advanced Materials 27, 169 (2015) and Nano Letters 17, 2640 (2017) and YGao et al. HSun and HVD, J Phys. Chem. Lett. 7, 2772 (2016)
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[6] BGuzelturk et al. HVD ACS Nano 8, 6599 (2014) and ACS Nano 8, 12524 (2014); M. Olutas et al. HVD, Advanced Functional Materials 26, 2891 (2016) and O. Erdem, et al. HVD J Phys. Chem. Lett. 7, 548 (2016)
[7] MSharma et al. HVD Advanced Materials, 29, 1700821 (2017)
[8] YKelestemur et al. HVD, Advanced Functional Materials 26, 3570 (2016) and Chemistry of Materials, 29, 4857 (2017)