Selective enhancement of surface-state emission and simultaneous quenching of interband transition in white-luminophor CdS nanocrystals using localized plasmon coupling

Özel, Tuncay; Soğancı, İbrahim Murat; Nizamoğlu, Sedat; Huyal, Ilkem Ozge; Mutlugün, Evren; Sapra, Sameer; Gaponik, Nikolai; Eychmüller, Alexander; Demir, Hilmi Volkan

doi:10.1088/1367-2630/10/8/083035

Cited by 41 publications

(37 citation statements)

References 25 publications

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“…9,10,23,24 The deep-trap emission often occurs in the metal chalcogenide NPs produced by low-temperature aqueous-phase syntheses. 2,9 Nevertheless, in the present case of the ultrasmall NPs, in which almost half of the atoms can be regarded as surface atoms, the key factor determining the PL emission can be the surface states rather than internal defects.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Raman and Infrared Phonon Spectra of Ultrasmall Colloidal CdS Nanoparticles

et al. 2014

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Raman and infrared phonon spectra of ultrasmall (1.8 nm) colloidal CdS nanoparticles (usNPs) are presented. Multiphonon scattering by optical phonons up to the third order is observed in the Raman spectra at low temperature and resonant (325 nm) excitation. The first-order optical phonon peak is a superposition of several components, two of which can be assigned to surface optical (SO) and longitudinal optical (LO) modes, respectively. The LO mode, being markedly broadened compared to that of spectra of regular (>2 nm) NPs, is related to phonon confinement and bond distortion induced by a significant structural relaxation in usNPs. A shoulder observed above the LO frequency is either due to the density of phonon states induced by distorted surface bonds or due to higher-order scattering processes involving optical and acoustic phonons. The Raman peaks of usNPs do not reveal the upward shift and narrowing upon decreasing temperature from 300 K down to 85 K typical for crystalline semiconductors, even though their intensity increases as expected. The abnormal thermal behavior of phonon peaks is likely related to the significant structural reorganization of the usNP lattice. A broad feature in the range of 200−300 cm −1 observed in the infrared phonon spectrum of usNPs correlates with the Raman data and is distinct from the SO mode previously reported for NPs of larger size. ■ INTRODUCTIONUltrasmall semiconductor nanoparticles (usNPs), or "magicsize" clusters, have recently attracted much attention due to their unique physical properties. 1−6 The growth rate of colloidal NPs deviates from the prediction of the classic thermodynamic growth theory as the NPs attain the magic closed-shell structure resulting from the existence of a chemical potential well. 6 For CdSe, CdS, and several other II−VI compounds, the most frequently observed magic structure comprises 32−34 molecular units corresponding to a diameter of around 1.7−1.9 nm. 1,6,7 The usNPs reveal either narrow blue 8 or broad-band quasi-white photoluminescence (PL), making this kind of NP promising for light-emission applications. [2][3][4]9,10 Studying NPs of such a small size is also of fundamental importance, as it allows the existing models to be verified in the regime of strong electron and phonon confinement. 11−15 Understanding and controlling the electronic and optical properties of usNPs is, however, complicated due to a considerable contribution from surface atoms, the number of which is comparable to the number of fully coordinated inner atoms, as well as due to the coupling between the electronic states in the NP and ligands. 16 The lattice vibration (phonon) spectra can provide valuable information on the structure and physical properties of semiconductor NPs and their interaction with the environment. 15−22 Here we report on resonant Raman scattering and infrared (IR) studies of phonons in CdS usNPs prepared by "wet" colloidal chemistry under mild conditions. We observe for the first time multiple Raman scattering by optical phonons up to the th...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Raman and Infrared Phonon Spectra of Ultrasmall Colloidal CdS Nanoparticles

et al. 2014

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“…The other route resembles the one reported by Rosenthal's group,48 combining surface‐state emissions with the band‐edge emission in plain nanocrystals to emit white light. This strategy was also employed by Ozel et al,83 who carefully integrated the silver nano‐island film with CdS nanocrystals in a poly(methyl methacrylate) matrix. Such careful integration could enhance the broad surface‐state emission and simultaneously suppress the band‐edge transition of CdS nanocrystals through matching their surface‐state emissions with the localized plasmon resonance of silver films.…”

Section: Semiconductor‐nanocrystals‐based Wledsmentioning

confidence: 99%

Semiconductor‐Nanocrystals‐Based White Light‐Emitting Diodes

Dai

Duty

2010

Small

239

169

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In response to the demands for energy and the concerns of global warming and climate change, energy efficient and environmentally friendly solid-state lighting, such as white light-emitting diodes (WLEDs), is considered to be the most promising and suitable light source. Because of their small size, high efficiency, and long lifetime, WLEDs based on colloidal semiconductor nanocrystals (or quantum dots) are emerging as a completely new technology platform for the development of flat-panel displays and solid-state lighting, exhibiting the potential to replace the conventionally used incandescent and fluorescent lamps. This replacement can cut the ever-increasing level of energy consumption, solve the problem of rapidly depleting fossil fuel reserves, and improve the quality of the global environment. In this review, the recent progress in semiconductor-nanocrystals-based WLEDs is highlighted, the different approaches for generating white light are compared, and the benefits and challenges of the solid-state lighting technology are discussed.

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“…In a recent study, an optimized non-injection method was developed to produce such Mn-doped QDs on a large scale [78], which were used to produce WLEDs with high CRI of 90 and CIE coordinates of (0.332, 0.321). Several kinds of white-emitting nanocrystals have been reported so far, such as trap-rich CdS QDs [79][80][81][82][83], magic-sized CdSe QDs [84][85][86][87][88], alloyed Zn x Cd 1-xSe(S) QDs [89,90], onion-like CdSe/ZnS/CdSe/ZnS QDs [80], and ZnSe QDs [91,92]. Their broad emission profiles typically combine the band-edge and the surface trap state emission.…”

Section: Wleds Based On Dual-color-emitting and White-emitting Qdsmentioning

confidence: 99%

Recent Progress in Quantum Dot Based White Light-Emitting Devices

Su,

Zhang,

Zhang

et al. 2016

Top Curr Chem (Z)

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Colloidal semiconductor quantum dots (QDs) have been widely employed as components of white light-emitting diodes (WLEDs) due to their excellent optical properties (highly saturated emission color, high luminescence quantum yield) as well as thermal and chemical stability. Much effort has been devoted to realize efficient QD-based WLEDs, including the synthesis of superior luminescent nanomaterials with excellent stabilities, and the design of advanced devices structures. In this paper, after introducing photometric parameters of the contemporary QD-based WLEDs, we highlight the recent progress in these devices grouped according to three main mechanisms for white light generation: optical excitation, direct charge carrier injection, and Förster resonance energy transfer. The methods to generate white light, the design of QD emitters and QD-based devices, as well as their fabrication techniques are considered, and the key scientific and technological challenges in the QD-based WLEDs are highlighted. Novel light-emitting materials for WLEDs such as carbon-based nanoparticles are also considered.

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Selective enhancement of surface-state emission and simultaneous quenching of interband transition in white-luminophor CdS nanocrystals using localized plasmon coupling

Cited by 41 publications

References 25 publications

Raman and Infrared Phonon Spectra of Ultrasmall Colloidal CdS Nanoparticles

Raman and Infrared Phonon Spectra of Ultrasmall Colloidal CdS Nanoparticles

Semiconductor‐Nanocrystals‐Based White Light‐Emitting Diodes

Recent Progress in Quantum Dot Based White Light-Emitting Devices

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