WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Zinc Chalcogenide Based Shell Layers for Colloidal Quantum Wells(Wiley, 2025-04-27) Aldemir, Cagatay Han; Yazici, Ahmet Faruk; Ergezer, Nehir; Korkmaz, Taha Can; Mutlugun, Evren; Kelestemur, YusufColloidal quantum wells, also known as colloidal nanoplatelets (NPLs), have emerged as a promising class of materials for light-emitting devices (LEDs). However, the most widely studied core/shell NPLs, which rely on cadmium-based shell layers, face challenges due to toxicity concerns and improper charge confinement. To address these limitations, a new synthetic approach is presented that enables the controlled growth of zinc chalcogenide-based shell layers on NPLs. The synthesized CdSe/ZnSe core/shell NPLs exhibit emission between 615 and 630 nm, with a moderate photoluminescence quantum yield (PL-QY) of 40-50%. It is also demonstrated that the lateral dimensions of the CdSe core NPLs significantly affect the optical properties of the core/shell heterostructures, with smaller lateral dimensions resulting in narrower emission linewidths as low as 20 nm. Further passivation of these core/shell NPLs with an additional ZnS shell layer significantly increases the PL-QY up to 80-90%. Finally, the device performance of these two core/shell NPLs is investigated by fabricating solution-processed LEDs. With LEDs incorporating CdSe/ZnSe/ZnS core/multi-shell NPLs as the active light-emitting layer, an external quantum efficiency (EQE) of 3.82% and a maximum brightness of 6477 cd m-2 is obtained. These findings underscore the significant potential of zinc chalcogenide-based shell layers in advancing colloidal NPLs toward high-performance light-emitting devices.Article Citation - WoS: 53Citation - Scopus: 59Thickness-Tunable Self-Assembled Colloidal Nanoplatelet Films Enable Ultrathin Optical Gain Media(Amer Chemical Soc, 2020-07-31) Erdem, Onur; Foroutan, Sina; Gheshlaghi, Negar; Guzelturk, Burak; Altintas, Yemliha; Demir, Hilmi VolkanWe propose and demonstrate construction of highly uniform, multilayered superstructures of CdSe/CdZnS core/shell colloidal nanoplatelets (NPLs) using liquid interface self-assembly. These NPLs are sequentially deposited onto a solid substrate into slabs having monolayer-precise thickness across tens of cm(2) areas. Because of near-unity surface coverage and excellent uniformity, amplified spontaneous emission (ASE) is observed from an uncharacteristically thin film having 6 NPL layers, corresponding to a mere 42 nm thickness. Furthermore, systematic studies on optical gain of these NPL superstructures having thicknesses ranging from 6 to 15 layers revealed the gradual reduction in gain threshold with increasing number of layers, along with a continuous spectral shift of the ASE peak (similar to 18 nm). These observations can be explained by the change in the optical mode confinement factor with the NPL waveguide thickness and propagation wavelength. This bottom-up construction technique for thickness-tunable, three-dimensional NPL superstructures can be used for large-area device fabrication.Article Citation - WoS: 13Citation - Scopus: 14Near-Field Energy Transfer Into Silicon Inversely Proportional to Distance Using Quasi-2D Colloidal Quantum Well Donors(Wiley-VCH Verlag GmbH, 2021-09-12) Humayun, Muhammad Hamza; Hernandez-Martinez, Pedro Ludwig; Gheshlaghi, Negar; Erdem, Onur; Altintas, Yemliha; Shabani, Farzan; Demir, Hilmi VolkanSilicon is the most prevalent material system for light-harvesting applications; however, its inherent indirect bandgap and consequent weak absorption limits its potential in optoelectronics. This paper proposes to address this limitation by combining the sensitization of silicon with extraordinarily large absorption cross sections of quasi-2D colloidal quantum well nanoplatelets (NPLs) and to demonstrate excitation transfer from these NPLs to bulk silicon. Here, the distance dependency, d, of the resulting Forster resonant energy transfer from the NPL monolayer into a silicon substrate is systematically studied by tuning the thickness of a spacer layer (of Al2O3) in between them (varied from 1 to 50 nm in thickness). A slowly varying distance dependence of d(-1) with 25% efficiency at a donor-acceptor distance of 20 nm is observed. These results are corroborated with full electromagnetic solutions, which show that the inverse distance relationship emanates from the delocalized electric field intensity across both the NPL layer and the silicon because of the excitation of strong in-plane dipoles in the NPL monolayer. These findings pave the way for using colloidal NPLs as strong light-harvesting donors in combination with crystalline silicon as an acceptor medium for application in photovoltaic devices and other optoelectronic platforms.