Stable and efficient colour enrichment powders of nonpolar nanocrystals in LiCl

Erdem, Talha; Soran‐Erdem, Zeliha; Sharma, Vijay Kumar; Keleştemur, Yusuf; Adam, Marcus; Gaponik, Nikolai; Demir, Hilmi Volkan

doi:10.1039/c5nr02696b

Cited by 16 publications

(43 citation statements)

References 17 publications

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“…On the other hand, 2ML CdSe NPLs synthesized using excess amount of Se exhibit almost purely broadband PL emission centered at ≈535 nm with a FWHM of ≈150 nm as shown in Figure a and a QY of 90% in solution. QY measurements were executed by following the procedure developed by De Mello et al at an excitation wavelength of 380 nm . We performed PL excitation (PLE) spectroscopy to probe the origin of the broadband emission.…”

Section: Resultsmentioning

confidence: 98%

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Delikanlı

Yeltik

et al. 2019

Adv Funct Materials

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Surface effects in atomically flat colloidal CdSe nanoplatelets (NLPs) are significantly and increasingly important with their thickness being reduced to subnanometer level, generating strong surface related deep trap photoluminescence emission alongside the bandedge emission. Herein, colloidal synthesis of highly luminescent two-monolayer (2ML) CdSe NPLs and a systematic investigation of carrier dynamics in these NPLs exhibiting broad photoluminescence emission covering the visible region with quantum yields reaching 90% in solution and 85% in a polymer matrix is shown. The astonishingly efficient Stokes-shifted broadband photoluminescence (PL) emission with a lifetime of ≈100 ns and the extremely short PL lifetime of around 0.16 ns at the bandedge signify the participation of radiative midgap surface centers in the recombination process associated with the underpassivated Se sites. Also, a proof-of-concept hybrid LED employing 2ML CdSe NPLs is developed as color converters, which exhibits luminous efficacy reaching 300 lm W opt −1 . The intrinsic absorption of the 2ML CdSe NPLs (≈2.15 × 10 6 cm −1 ) reported in this study is significantly larger than that of CdSe quantum dots (≈2.8 × 10 5 cm −1 ) at their first exciton signifying the presence of giant oscillator strength and hence making them favorable candidates for next-generation light-emitting and light-harvesting applications.

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Section: Resultsmentioning

confidence: 98%

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Delikanlı

Yeltik

et al. 2019

Adv Funct Materials

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“…[40] We measured the fluorescence quantum yield of the polymer and polyrotaxane solutions in water using the method described in refs. [30] and [41].…”

Section: Optical Characterizationsmentioning

confidence: 99%

“…Otto et al showed that the quantum dots in water can be successfully incorporated into crystalline salt matrices. Later, this approach was shown to improve the fluorescence QY, and emission stability . Moreover, this method was also extended to nonionic crystals including sucrose and anthracene and to quantum dots in nonpolar solvents and applied in light‐emitting diodes (LEDs) and sensors .…”

Section: Introductionmentioning

confidence: 99%

“…Later, this approach was shown to improve the fluorescence QY, and emission stability . Moreover, this method was also extended to nonionic crystals including sucrose and anthracene and to quantum dots in nonpolar solvents and applied in light‐emitting diodes (LEDs) and sensors . Recently, our group has evaluated the potential of this technique by incorporating the conjugated oligomer nanoparticles, which are essentially wrapped in the form of nanoscale balls of oligomers in sucrose crystals .…”

Section: Introductionmentioning

confidence: 99%

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Highly Luminescent CB[7]‐Based Conjugated Polyrotaxanes Embedded into Crystalline Matrices

Erdem

Idris

Demir

et al. 2017

Macro Materials & Eng

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they pose significantly lower risks to environment and health compared to other optical materials such as cadmiumbased quantum dots [10] and lead-based perovskites. [11] Despite the potential of conjugated polymers, a decrease in the fluorescence quantum yield (QY) and a low emission stability in their solid state turn out to be an important bottleneck. These problems mainly arise from the changes in the polymer morphology upon film casting, which affects the inter and intrachain interactions. To decrease these interactions and consequently, achieve higher QYs in solid films, various approaches have been adopted including the utilization of nonradiative energy transfer to light-emitting polymers [12,13] and the incorporation of the polymers into inorganic nanoparticles. [14][15][16] Alternatively, chemical entities such as dendrones have been attached to the polymer backbone in order to weaken the π-π stacking.[17] Insulation of the conjugated polymer backbones via rotaxanation, which can be considered as threading the polymer chain using a macrocyclic ring, also steps forward as a promising solution. [18][19][20] In the literature, cyclodextrins and cucurbit[n]urils (CB[n]) have been shown to successfully isolate the polymer backbone leading to enhanced fluorescence QY. [21][22][23][24][25][26] For instance, our group has recently demonstrated fourfold increase in the fluorescence QY of poly(9,9′-bis(6″-(N,N,N-trimethylammonium)hexyl)fluorene-alt-co-thiophenelene) accompanied by blue-shifted fluorescence spectrum and prolonged fluorescence lifetime after threading with CB7. [27] Despite the improvements in the QY of polyrotaxane solutions, their solid films still suffered from decreased fluorescence QY. Therefore, a solution to maintain the fluorescence QY is of significant importance for their use in solid-state lighting.A possible solution to this problem might come from the research on the colloidal quantum dots, which similarly suffered from decreasing QYs in their solid films. Otto et al. [28] showed that the quantum dots in water can be successfully incorporated into crystalline salt matrices. Later, this approach was shown to improve the fluorescence QY, [29] and emission stability. [30,31] Moreover, this method was also extended to nonionic crystals including sucrose [32] and anthracene [33] and to quantum dots in nonpolar solvents [30,34] and applied in lightemitting diodes (LEDs) [31] and sensors. [35] Recently, our group has evaluated the potential of this technique by incorporating π-Conjugated Polyrotaaxanes π-Conjugated polymers suffer from low quantum yields (QYs) due to chainchain interactions. Furthermore, their emission in solid films is significantly quenched due to aggregation leading further decrease in QY. These are the two main issues of these materials hampering their widespread use in optoelectronic devices. To address these issues, here the backbone of poly(9,9′-bis (6″-(N,N,N-trimethylammonium)hexyl)fluorene-alt-co-thiophenelene) is isolated by threading with cucurbit[7]uril (CB7). Su...

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“…Nonetheless, it is well known that such a ligand exchange procedure can significantly decrease the efficiency of the QDs. Our group addressed this issue by specifically employing LiCl as the host matrix [35], which can be dissolved in tetrahydrofuran. Since the nonpolar QDs can also be dispersed in tetrahydrofuran, incorporation of the nonpolar QDs into LiCl has been possible without ligand exchange.…”

Section: Color-converting Colloidal Materials For Lightingmentioning

confidence: 99%

Colloidal nanocrystals for quality lighting and displays: milestones and recent developments

Erdem

Demir

2016

Nanophotonics

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Recent advances in colloidal synthesis of nanocrystals have enabled high-quality high-efficiency light-emitting diodes, displays with significantly broader color gamut, and optically-pumped lasers spanning the whole visible regime. Here we review these colloidal platforms covering the milestone studies together with recent developments. In the review, we focus on the devices made of colloidal quantum dots (nanocrystals), colloidal quantum rods (nanorods), and colloidal quantum wells (nanoplatelets) as well as those of solution processed perovskites and phosphor nanocrystals. The review starts with an introduction to colloidal nanocrystal photonics emphasizing the importance of colloidal materials for light-emitting devices. Subsequently, we continue with the summary of important reports on light-emitting diodes, in which colloids are used as the color converters and then as the emissive layers in electroluminescent devices. Also, we review the developments in color enrichment and electroluminescent displays. Next, we present a summary of important reports on the lasing of colloidal semiconductors. Finally, we summarize and conclude the review presenting a future outlook.

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Stable and efficient colour enrichment powders of nonpolar nanocrystals in LiCl

Cited by 16 publications

References 17 publications

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Highly Luminescent CB[7]‐Based Conjugated Polyrotaxanes Embedded into Crystalline Matrices

Colloidal nanocrystals for quality lighting and displays: milestones and recent developments

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