title: Lateral Size-Dependent Spontaneous and Stimulated Emission Properties in Colloidal CdSe Nanoplatelets.
abstract: Here, we systematically investigated the spontaneous and stimulated emission performances of solution-processed atomically flat quasi-2D nanoplatelets (NPLs) as a function of their lateral size using colloidal CdSe core NPLs. We found that the photoluminescence quantum efficiency of these NPLs decreases with increasing lateral size while their photoluminescence decay rate accelerates. This strongly suggests that nonradiative channels prevail in the NPL ensembles having extended lateral size, which is well-explained by the increasing number of the defected NPL subpopulation. In the case of stimulated emission the role of lateral size in NPLs influentially emerges both in the single- and two-photon absorption (1PA and 2PA) pumping. In the amplified spontaneous emission measurements, we uncovered that the stimulated emission thresholds of 1PA and 2PA exhibit completely opposite behavior with increasing lateral size. The NPLs with larger lateral sizes exhibited higher stimulated emission thresholds under 1PA pumping due to the dominating defected subpopulation in larger NPLs. On the other hand, surprisingly, larger NPLs remarkably revealed lower 2PA-pumped amplified spontaneous emission thresholds. This is attributed to the observation of a "giant" 2PA cross-section overwhelmingly growing with increasing lateral size and reaching record levels higher than 10(6) GM, at least an order of magnitude stronger than colloidal quantum dots and rods. These findings suggest that the lateral size control in the NPLs, which is commonly neglected, is essential to high-performance colloidal NPL optoelectronic devices in addition to the vertical monolayer control.
authors.affiliation: †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey.|‡Department of Physics, Abant Izzet Baysal University, Bolu 14280, Turkey.
authors.forename: Murat
authors.initials: M
authors.lastname: Olutas
authors.affiliation: †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey.
authors.forename: Burak
authors.initials: B
authors.lastname: Guzelturk
authors.affiliation: †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey.
authors.forename: Yusuf
authors.initials: Y
authors.lastname: Kelestemur
authors.affiliation: †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey.
authors.forename: Aydan
authors.initials: A
authors.lastname: Yeltik
authors.affiliation: †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey.
authors.forename: Savas
authors.initials: S
authors.lastname: Delikanli
authors.affiliation: †Department of Electrical and Electronics Engineering, Department of Physics, UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800 Turkey.|§Luminous! Center of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Hilmi Volkan
authors.initials: HV
authors.lastname: Demir
keywords: amplified spontaneous emission; colloidal quantum wells; giant two-photon absorption cross-section; lateral size; photoluminescence quantum efficiency; semiconductor nanoplatelets; stimulated emission