Electroluminescence from isolated CdSe∕ZnS quantum dots in multilayered light-emitting diodes

Zhao, Jialong; Zhang, Jingying; Jiang, Chaoyang; Bohnenberger, Jolanta; Basché, Thomas; Mews, Alf

doi:10.1063/1.1784611

Cited by 143 publications

(93 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[29] The increase in peak width of the EL is likely to be an effect of both environmental broadening and local heating of the sample under current flow. [25] In conclusion, we have reported a method to control the sequential growth of CdSe magic-size clusters of progressively larger sizes. We modeled the time evolution of the concentration of the various magic sizes using a slight modification of a continuous-growth model.…”

mentioning

confidence: 98%

Sequential Growth of Magic‐Size CdSe Nanocrystals

et al. 2007

View full text Add to dashboard Cite

Colloidal semiconductor nanocrystals have been exploited in several applications in which they serve as fluorophores, because of the tunability of the wavelength of the emitted light. [1][2][3] The possibility of exactly controlling the size of nanocrystals is of great importance in the development of these materials, as this will lead to nano-objects with well-defined and reproducible properties. Whereas this goal seems to be hard to achieve with large nanocrystals, it might be viable for clusters consisting of a few tens or hundreds of atoms, as in this size regime a handful of structures can have an exceptionally high stability and therefore would form preferentially over any other combination of atoms. This concept is already well-known for several metal clusters, as for some of them several "magic" structures exist that are formed by closed shells of atoms. [4][5][6][7] Cluster molecules that can be considered as the smallest building units of semiconductors have been investigated in the past.As an example several tetrahedral cluster molecules based on the general formula [z-(where E = S or Se; M = Zn or Cd; and R = alkyl or aryl) or similar were reported some years ago. [8,9] The series was formed only by clusters containing a well-defined number of atoms, and therefore, characterized by particularly stable structures; thus, these structures can also be termed "magic-size clusters" (MSCs). Different families of almost monodisperse CdS clusters of sizes down to 1.3 nm were reported by Vossmeyer et al., [10] whereas CdSe MSCs were observed later in the solution growth of colloidal nanocrystals [11] and the various cluster sizes found were explained as arising from the aggregation of smaller clusters. Soloviev et al. synthesized and crystallized a homologous series of CdSe cluster molecules [12,13] (very similar in structure to those reported earlier [8,9] ) that were capped by selenophenol ligands. Also in many high-temperature organometallic syntheses of colloidal CdSe nanocrystals, either the transient formation of ultrasmall, highly stable CdSe clusters was noticed, [14,15] or these clusters could be isolated using size-selective precipitation. [16,17] Recently, one type of CdSe MSC has been synthesized in a water-in-oil reverse-micelle system.[18]Here, we report a method for controlling the sequential growth in solution of CdSe MSCs of progressively larger sizes. Each of these types of clusters is characterized by a sharp optical-absorption feature at a well-defined energy. During the synthesis, the relative populations of the different families of MSCs varied, as smaller MSCs evolved into larger MSCs. We can model the time evolution of the concentration of the various magic sizes using a modification of a continuous-growth model, by taking into account the much higher stability of the various MSCs over nanocrystals of any intermediate size.For the synthesis of the CdSe MSCs reported here a mixture of dodecylamine and nonanoic acid was used to decompose cadmium oxide at 200°C under an inert atmosphere. Th...

show abstract

mentioning

confidence: 98%

Sequential Growth of Magic‐Size CdSe Nanocrystals

et al. 2007

View full text Add to dashboard Cite

show abstract

“…In the first device layout, a thin QD layer is sandwiched between a hole and electron injection layer such that excitons are formed directly in the QD layer. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] In the second layout, the active layer consists of a blend of QDs dispersed in a polymer [29][30][31][32][33][34][35][36][37][38][39] or small molecule matrix. 40,41 The QDs in this composite material serve as emissive traps for ͑migrating͒ excitons that are generated in the polymer matrix by charge carrier recombination.…”

Section: Introductionmentioning

confidence: 99%

Energy transfer in hybrid quantum dot light-emitting diodes

Chin

Hikmet

Janssen

2008

Journal of Applied Physics

View full text Add to dashboard Cite

Energy transfer in a host-guest system consisting of a blue-emitting poly͑2,7-spirofluorene͒ ͑PSF͒ donor and red-emitting CdSe/ ZnS core shell quantum dots ͑QDs͒ as acceptor is investigated in solid films, using time-resolved optical spectroscopy, and in electroluminescent diodes. In the QD:PSF composite films, the Förster radius for energy transfer is found to be 4 -6 nm. In electroluminescent devices lacking an electron transport layer, the electroluminescence ͑EL͒ spectrum of the QD:PSF polymer composite is similar to the photoluminescence ͑PL͒, giving evidence for energy transfer from PSF to the QDs. The addition of an electron transport layer between the emitting layer and the cathode results in a significant change in the EL spectrum and a considerable improved device performance, providing almost pure monochromatic emission at 630 nm with a luminance efficiency of 0.32 cd/ A. The change in spectrum signifies that the electron transport layer changes the dominant pathway for QD emission from energy transfer from the polymer host to direct electron-hole recombination on the QDs.

show abstract

“…The QD charging process can change with the film thickness or surface roughness owing to variations in the local space charges or because of local Joule heating. [20,21] The presence of a negligible a-NPD (420 nm) emission suggests hole accumulation at the HIL/HTL and a-NPD/CBP interfaces owing to the alignment of the highest occupied molecular orbital (HOMO) levels. [22] The HBL is effective in precluding the transfer of holes and excitons into the ETL, Alq 3 , and thus inhibits emission from the ETL.…”

mentioning

confidence: 99%

Hybrid Light‐Emitting Diodes from Microcontact‐Printing Double‐Transfer of Colloidal Semiconductor CdSe/ZnS Quantum Dots onto Organic Layers

et al. 2008

View full text Add to dashboard Cite

Colloidal semiconductor nanocrystals have been attracting increasing technological interest for applications in lighting and flat-panel display applications. [1][2][3][4][5][6][7] In particular, continuing improvements in synthetic methods have enabled the design of high-quality quantum dot (QD) structures with photoluminescence (PL) ranging across the visible spectrum, a PL full width at half maximum (FWHM) less than 30 nm, and a PL efficiency higher than 50%.

show abstract

Electroluminescence from isolated CdSe∕ZnS quantum dots in multilayered light-emitting diodes

Cited by 143 publications

References 28 publications

Sequential Growth of Magic‐Size CdSe Nanocrystals

Sequential Growth of Magic‐Size CdSe Nanocrystals

Energy transfer in hybrid quantum dot light-emitting diodes

Hybrid Light‐Emitting Diodes from Microcontact‐Printing Double‐Transfer of Colloidal Semiconductor CdSe/ZnS Quantum Dots onto Organic Layers

Contact Info

Product

Resources

About