Browsing by Subject "Quantum dots"

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Open Access
Advances in fiber sensing devices decorated with functionalized nanomaterials
(2023-05-08) Yıldırım, Elif Yapar; Karatutlu, Ali
Hybrid sensor devices formed via decoration of nanomaterials on the surface of optical fibers are designed and fabricated for sensing specific physical, chemical, or biological objects. In this chapter, advances in optical fiber sensing devices functionalized with nanomaterials are outlined with respect to optical fiber types including the optical fiber sensing device preparation processes, detection object, sensitivity, and their sensing mechanism. The single- and multimode fibers, active fibers, fiber Bragg gratings, and photonic crystal fibers are the mostly utilized forms of optical fiber sensing devices. The emerging functionalized nanomaterials reviewed here are limited to quantum dots, plasmonic nanoparticles (NPs), 2D nanomaterials, and rare earth–doped NPs.
Open Access
Assembly kinetics of nanocrystals via peptide hybridization
(American Chemical Society, 2011-03-16) Seker U.O.S.; Zengin, G.; Tamerler, C.; Sarikaya, M.; Demir, Hilmi Volkan
The assembly kinetics of colloidal semiconductor quantum dots (QDs) on solid inorganic surfaces is of fundamental importance for implementation of their solid-state devices. Herein an inorganic binding peptide, silica binding QBP1, was utilized for the self-assembly of nanocrystal quantum dots on silica surface as a smart molecular linker. The QD binding kinetics was studied comparatively in three different cases: first, QD adsorption with no functionalization of substrate or QD surface; second, QD adsorption on QBP1-modified surface; and, finally, adsorption of QBP1-functionalized QD on silica surface. The surface modification of QDs with QBP1 enabled 79.3-fold enhancement in QD binding affinity, while modification of a silica surface with QBP1 led to only 3.3-fold enhancement. The fluorescence microscopy images also supported a coherent assembly with correspondingly increased binding affinity. Decoration of QDs with inorganic peptides was shown to increase the amount of surface bound QDs dramatically compared to the conventional methods. These results offer new opportunities for the assembly of QDs on solid surfaces for future device applications.
Open Access
Blue liquid lasers from solution of CdZnS/ZnS ternary alloy quantum dots with quasi ‐ continuous pumping
(Wiley - VCH Verlag GmbH & Co. KGaA, 2015) Wang Y.; Leck K.S.; Ta, V. D.; Chen R.; Nalla, V.; Gao, Y.; He T.; Demir, Hilmi Volkan; Sun, H.
A blue (ca. 440 nm) liquid laser with an ultra‐low threshold through which quasi‐continuous wave pumping is accessible is achieved by engineering unconventional ternary CdZnS/ZnS alloyed‐core/shell QDs. Such an achievement is enabled by exploiting the novel gain media with minimal defects, suppressed Auger recombination, and large gain cross‐section in combination with high‐quality‐factor whispering gallery mode resonators.
Open Access
Bright White-Light Emitting Manganese and Copper Co-Doped ZnSe Quantum Dots
(Wiley, 2011) Panda, S. K.; Hickey, S. G.; Demir, Hilmi Volkan; Eychmuller, A.
Doubly doped quantum dots with highly efficient (17 %) white-light emission (WLE) have been directly synthesized using a one-pot hot-injection technique (see picture). The generation of WLE was due to the judicious manipulation of the synthesis strategy for the co-doping of the host material-ZnSe quantum dots-with Mn and Cu.
Open Access
Brightly luminescent Cu-Zn-In-S/ZnS Core/shell quantum dots in salt matrices
(De Gruyter, 2019) Lox, J. F. L.; Eichler, F.; Erdem, Talha; Adam, M.; Gaponik, N.; Demir, Hilmi Volkan; Lesnyak, V.; Eychmüller, A.
In the past decades cadmium-free quantum dots (QDs), among which are quaternary colloidal Cu-Zn-In-S/ZnS (CZIS/ZnS) core/shell nanocrystals (NCs), have attracted great scientific interest. Particularly, their low toxicity and the possibility to tune their photoluminescence (PL) properties by varying the composition in the multicomponent system make them highly attractive for applications in light-emitting diodes (LEDs). Thus, the demands for high quality CZIS/ZnS QDs and methods to process them into bulk materials stimulate investigations of these nanomaterials. Herein, we demonstrate the synthesis of CZIS/ZnS core/shell NCs via a surfactant induced nucleation process, which emit in various colors covering the range from 520 nm to 620 nm possessing high photoluminescence quantum yields (PLQYs) up to 47%. Furthermore, the as synthesized NCs were successfully integrated into two different salt matrices [Na2B4O7 (Borax) and LiCl] using two different approaches. The commonly used incorporation of the NCs into Borax salt led to salt crystals emitting from 540 nm to 600 nm with PLQYs up to 24%. By encapsulating the QDs into LiCl, brightly emitting NCs-in-LiCl powders with the PL covering a range from 520 nm to 650 nm with PLQYs of up to 14% were obtained. As a proof of concept, the fabrication of a color conversion LED using NCs encapsulated into LiCl demonstrated the applicability of the encapsulated NCs.
Open Access
Colloidal heterostructures of semiconductor quantum wells : synthesis, characterization and applications
(2017-06) Keleştemur, Yusuf
Colloidal semiconductor quantum wells, also known as nanoplatelets (NPLs), have recently emerged as a new class of colloidal semiconductor nanocrystals enabling fascinating excitonic properties. With their quasi two-dimensional structure resembling epitaxially-grown quantum wells, these atomically- at nanoplatelets exhibit narrow emission linewidths, giant linear and nonlinear absorption cross-sections, and ultrafast uorescence lifetimes when compared to other classes of semiconductor nanocrystals. These appealing features have led to achievement of low lasing thresholds and high color purity by using simple heterostructures of these NPLs. To further exploit the benefits of these solutionprocessed NPLs and develop next-generation colloidal optoelectronic devices, novel heterostructures of NPLs with superior excitonic properties are in high demand. In this thesis, to address these needs, we proposed and demonstrated novel heterostructured NPLs. This thesis includes the rational design and systematic synthesis and characterization of these hetero-NPLs. To overcome the lower photoluminescence quantum yield (PL-QY) and stability issues of core/shell NPLs, we successfully synthesized CdSe/CdS/CdS core/crown/shell NPLs resembling platelet-in-a-box. With this advanced architecture, we accomplished substantially enhanced PL-QY and absorption crosssection as well as stability, allowing for the achievement of low-threshold optical gain. However, due to the pure vertical confinement observed in these NPLs, these exciting excitonic features of NPLs suffered from the limited spectral tunability. By developing homogenously alloyed CdSexS1 NPLs together with their alloyed core/crown and alloyed core/shell heterostructures, we succeeded in obtaining highly tunable excitonic features and further extending tunability of the optical gain from these NPLs. In addition to the NPLs having Type-I electronic structure, we demonstrated the highly uniform growth of CdSe/CdTe core/crown NPLs having Type-II electronic structure exhibiting unique excitonic properties Additionally, to realize the evolution of Type-II electronic structure, we synthesized CdSe/CdSe1-xTex core/crown NPLs by precisely tailoring the composition of the crown region. Without changing their vertical thicknesses, we achieved again highly tunable excitonic features and near-unity PL-QY from these hetero- NPLs. Based on the proposed architectures of these heteronanoplatelets, we believe the findings of this thesis provide important guidelines and inspiration for the synthesis of highly efficient and stable heterostructured NPLs to construct high-performance colloidal optoelectronic devices, possibly challenging their conventional epitaxially-grown counterparts.
Open Access
Colloidal Nanocrystals Embedded in Macrocrystals: Robustness, Photostability, and Color Purity
(American Chemical Society, 2012-09-14) Otto, T.; Mueller, M.; Mundra, P.; Lesnyak, V.; Demir, Hilmi Volkan; Gaponik N.; Eychmuller, A.
The incorporation of colloidal quantum dots (QDs) into ionic crystals of various salts (NaCl, KCl, KBr, etc.) is demonstrated. The resulting mixed crystals of various shapes and beautiful colors preserve the strong luminescence of the incorporated QDs. Moreover, the ionic salts appear to be very tight matrices, ensuring the protection of the QDs from the environment and as a result providing them with extraordinary high photo- and chemical stability. A prototype of a white light-emitting diode (WLED) with a color conversion layer consisting of this kind of mixed crystals is demonstrated. These materials may also find applications in nonlinear optics and as luminescence standards.
Open Access
Colloidal semiconductor nanocrystals
(Springer Singapore, 2022-10-28) Erdem, Onur; Demir, Hilmi Volkan
In this chapter, we review colloidal semiconductor nanocrystals (NCs) and their remarkable size-dependent properties. We emphasize on colloidal nanoplatelets and explain how they differ from NCs of other classes.
Open Access
Color-enrichment semiconductor nanocrystals for biorhythm-friendly backlighting
(De Gruyter, 2018) Erdem, T.; Demir, Hilmi Volkan
Nanocrystals (NCs) offer great opportunities for developing novel light-emitting devices possessing superior properties such as high quality indoor lighting, efficient outdoor lighting, and display backlighting with increased color definition. The narrow-band emission spectra of these materials also offer opportunities to protect the human daily biological rhythm against the adverse effects of display backlighting. For this purpose, here we address this problem using color converting NCs and analyzed the effect of the NC integrated color converting light-emitting diode (NC LED) backlight spectra on the human circadian rhythm. We employed the three existing models including the circadian light, the melanopic sensitivity function, and the circadian effect factor by simultaneously satisfying the National Television Standards Committee (NTSC) requirements. The results show that NC LED backlighting exhibits (i) 33% less disruption on the circadian cycle if the same color gamut of the commercially available YAG:Ce LED is targeted and (ii) 34% wider color gamut while causing 4.1% weaker disruption on the circadian rhythm compared to YAG:Ce LED backlight if the NTSC color gamut is fully reproduced. Furthermore, we found out that blue and green emission peaks have to be located at 465 with 30 nm bandwidth and at 535 nm with 20 nm bandwidth, respectively, for a circadian rhythm friendly design while the red component offers flexibility around the peak emission wavelength at 636 nm as opposed to the requirements of quality indoor lighting. These design considerations introduced as a new design perspective for the displays of future will help avoiding the disruption of the human circadian rhythm.
Embargo
Core-shell quantum dot-embedded polymers for antistatic applications
(American Chemical Society, 2023-12-07) Ekim, Sunay Dilara; Aydın, Firdevs; Kaya, Görkem Eylül; Baytekin, H. Tarık; Asil, Demet; Baytekin, Bilge
Electrical charges develop on the surfaces of two insulator materials when they are in contact and separated. The retention of charges on insulator polymers causes material losses and hazards in industries using these polymers. Here, we show that a set of core-shell quantum dots embedded into a common polymer can destabilize the charges on the polymer. The locations of the charge carriers in the nanostructure, or the “type” of the dots, affect their discharging ability, which can also be manipulated or reverted remotely by light. The mechanism of antistatic action is presumed to contain interaction with polymer mechanospecies. The quantum dot embedding renders the polymers antistatic without changing their conductivity. Such antistatic additives, by which the polymers remain insulating, can be used to prevent static charges, e.g., in electronic coatings and in other antistatic applications.
Open Access
Coulomb drag effect in parallel quantum dots
(American Institute of Physics, 2009) Tanatar, Bilal; Moldoveanu, V.
We study theoretically the electronic transport in parallel few-level quantum dots in the presence of both intradot and interdot long-range Coulomb interaction. Each dot is connected to two leads and the steady-state currents are calculated within the Keldysh formalism using the random-phase approximation for the interacting Green functions. Due to the momentum transfer mechanism between the two systems it is possible to get a nonvanishing current through an unbiased Coulomb-blockaded dot if the other dot is set in the nonlinear transport regime. The transitions between the levels of the passive dot reduce the drag current and lead to negative differential conductance.
Open Access
Droplet-based microfluidic systems for silica coating and synthesis of conjugated polymer nanoparticles
(2015-07) Özkan, Alican
Nanoparticles have unique electronic, optic and magnetic properties due to their large area to volume ratio. In order for them to preserve their properties for longer times, some of them need to be coated with a protective layer such as silica (silicon dioxide) layer. This coating has to be made uniformly to obtain monodisperse size distributions, which is essential to obtain uniform properties for all nanoparticles. Obtaining monodisperse size distribution relies on the control over reaction conditions such as residence time, concentration and temperature. This thesis presents a microuidic reactor that can achieve strict control over reaction conditions by utilizing a meandering geometry of microchannels and droplet-based ow. Meandering channels reduce the time needed for mixing due to the reduced diffusion lengths; whereas droplet-based flow provides uniform residence time inside the reactor due to the circulating flow profile of droplets as opposed to parabolic ow profile in straight channels. Before fabricating the device, the mixing performance of droplets at different channel cross-sections and meandering geometries were simulated by using Comsol Multiphysicsr. As a result, it is concluded that the channel cross-section and meandering dimensions should be as small as possible for faster mixing. Based on these simulation results, the microuidic device was designed and later fabricated in polydimethyl siloxane (PDMS) by using the soft lithography technique. This system was used to understand the effect of solvent concentrations and residence time on silica formation in order to be able to control the coating thickness compared to batchwise methods. Initially silica nanoparticle formation inside droplets were tested; and 102 nm ± 4 nm diameter of silica nanoparticles were obtained; which is a significant improvement compared to the bath-wise synthesis methods. Additionally, experimental studies on the synthesis of green Conjugated Polymer Nanoparticles (CPN) was also conducted. By using three different methods, bulk solution, continuous ow and droplet-based ow, nanoparticles were synthesized. From the results, it was acquired that droplet-based ow provided higher quality of nanoparticles in terms of nanoparticle size, uniformity and monodispersity.
Open Access
Electrically control amplified spontaneous emission in colloidal quantum dots
(American Association for the Advancement of Science, 2019) Yu, J.; Shendre, S.; Koh, W.; Liu, B.; Li, M.; Hou, S.; Hettiarachchi, C.; Delikanlı, S.; Hernandez-Martinez, P.; Birowosuto, M. D.; Wang, H.; Sum, T.; Demir, Hilmi Volkan; Dang, C.
Colloidal quantum dots (CQDs) are highly promising materials for light amplification thanks to their efficient photoluminescence, tunable emission wavelength and low-cost synthesis. Unfortunately, CQDs are suffering from band-edge state degeneracy which demands multiple excitons to achieve population inversion. As a result, non-radiative Auger recombination increases the lasing threshold and limits the gain lifetime. Here, benefiting from the negative charging, we demonstrate that the amplified spontaneous emission (ASE) threshold is controllable in a device where CQD film is exposed to an external electric field. Specifically, singly charged CQDs lower the threshold due to the preexisting electron in the conduction band, while strongly enhanced Auger recombination in doubly charged CQDs stymies the ASE. Experimental results and kinetic equation model show that ASE threshold reduces 10% even if our device only charges ~17% of the CQD population. Our results open new possibilities for controlling exciton recombination dynamics and achieving electrically pumped CQD lasers.
Open Access
Electro-optic modulation of InAs quantum dot waveguides
(Technische Universiteit Eindhoven, 2008) Akça, İmran. B.; Dâna, Aykutlu; Aydınlı, Atilla; Rossetti, M.; Li, L.; Fiore, A.; Dağlı, N.
The linear electro-optic properties in waveguides containing self-organized In As quantum dots were studied experimentally. Fabry-Perot measurements at 1515 nm on InAs/GaAs quantum dot structures yield a significantly enhanced linear electro-optic efficiency compared to bulk GaAs.
Open Access
Electroluminescence efficiency enhancement in quantum dot light-emitting diodes by embedding a silver nanoisland layer
(Wiley-VCH Verlag, 2015) Yang, X.; Hernandez-Martinez, P. L.; Dang C.; Mutlugün, E.; Zhang, K.; Demir, Hilmi Volkan; Sun X. W.
A colloidal quantum dot light-emitting diode (QLED) is reported with substantially enhanced electroluminescence by embedding a thin layer of Ag nanoislands into hole transport layer. The maximum external quantum efficiency (EQE) of 7.1% achieved in the present work is the highest efficiency value reported for green-emitting QLEDs with a similar structure, which corresponds to 46% enhancement compared with the reference device. The relevant mechanisms enabling the EQE enhancement are associated with the near-field enhancement via an effective coupling between excitons of the quantum dot emitters and localized surface plasmons around Ag nano-islands, which are found to lead to good agreement between the simulation results and the experimental data, providing us with a useful insight important for plasmonic QLEDs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Open Access
Enhanced spontaneous emission in semiconductor nanocrystal solids using resonant energy transfer for integrated devices
(IEEE, 2008-11) Nizamoğlu, Sedat; Demir, Hilmi Volkan
Size-tuneable optical properties of semiconductor nanocrystal (NC) quantum dots make them attractive for a wide range of device applications. However, in these device applications, nanocrystals typically suffer from relatively low quantum efficiency (QE) when they are cast into solid form. To reduce the effect of this problem, we propose and demonstrate the enhancement of spontaneous emission in nanocrystal solids by recycling their trapped excitons through resonant nonradiative Forster energy transfer (ET) for hybrid integrated devices. For this purpose, we designed closely packed CdSe/ZnS core/shell nanocrystal emitters with an energy gradient of approximately 160 meV integrated on LEDs.
Open Access
Highly stable multicrown heterostructures of type-II nanoplatelets for ultralow threshold optical gain
(American Chemical Society, 2019) Dede, Didem; Taghipour, Nima; Quliyeva, Ulviyya; Sak, Mustafa; Kelestemur, Yusuf; Güngör, Kıvanç; Demir, Hilmi Volkan
Solution-processed type-II quantum wells exhibit outstanding optical properties, which make them promising candidates for light-generating applications including lasers and LEDs. However, they may suffer from poor colloidal stability under ambient conditions and show strong tendency to assemble into face-to-face stacks. In this work, to resolve the colloidal stability and uncontrolled stacking issues, we proposed and synthesized CdSe/CdSe1–xTex/CdS core/multicrown heteronanoplatelets (NPLs), controlling the amount of Te up to 50% in the crown without changing their thicknesses, which significantly increases their colloidal and photostability under ambient conditions and at the same time preserving their attractive optical properties. Confirming the final lateral growth of CdS sidewalls with X-ray photoelectron spectroscopy, energy-dispersive analysis, and photoelectron excitation spectroscopy, we found that the successful coating of this CdS crown around the periphery of conventional type-II NPLs prevents the unwanted formation of needle-like stacks, which results in reduction of the undesired scattering losses in thin-film samples of these NPLs. Owing to highly efficient exciton funneling from the outmost CdS crown accompanied by the reduced scattering and very low waveguide loss coefficient (∼18 cm–1), ultralow optical gain thresholds of multicrown type-II NPLs were achieved to be as low as 4.15 μJ/cm2 and 2.48 mJ/cm2 under one- and two-photon absorption pumping, respectively. These findings indicate that the strategy of using engineered advanced heterostructures of nanoplatelets provides solutions for improved colloidal stability and enables enhanced photonic performance.
Open Access
Implementation of high-quality warm-white light-emitting diodes by a model-experimental feedback approach using quantum dot-salt mixed crystals
(American Chemical Society, 2015) Adam, M.; Erdem, T.; Stachowski, G.M.; Soran-Erdem Z.; Lox, J. F. L.; Bauer, C.; Poppe, J.; Demir, Hilmi Volkan; Gaponik N.; Eychmüller A.
In this work, a model-experimental feedback approach is developed and applied to fabricate high-quality, warm-white light-emitting diodes based on quantum dots (QDs) as color-conversion materials. Owing to their unique chemical and physical properties, QDs offer huge potential for lighting applications. Nevertheless, both emission stability and processability of the QDs are limited upon usage from solution. Incorporating them into a solid ionic matrix overcomes both of these drawbacks, while preserving the initial optical properties. Here borax (Na2B4O7·10H2O) is used as a host matrix because of its lower solubility and thereby reduced ionic strength in water in comparison with NaCl. This guarantees the stability of high-quality CdSe/ZnS QDs in the aqueous phase during crystallization and results in a 3.4 times higher loading amount of QDs within the borax crystals compared to NaCl. All steps from the synthesis via mixed crystal preparation to the warm-white LED preparation are verified by applying the model-experimental feedback, in which experimental data and numerical results provide feedback to each other recursively. These measures are taken to ensure a high luminous efficacy of optical radiation (LER) and a high color rendering index (CRI) of the final device as well as a correlated color temperature (CCT) comparable to an incandescent bulb. By doing so, a warm-white LED with a LER of 341 lm/Wopt, a CCT of 2720 K and a CRI of 91.1 is produced. Finally, we show that the emission stability of the QDs within the borax crystals on LEDs driven at high currents is significantly improved. These findings indicate that the proposed warm-white light-emitting diodes based on QDs-in-borax hold great promise for quality lighting. © 2015 American Chemical Society.
Open Access
Innovative hybrid composite nanomaterials
(2016-09) Erdem, Zeliha Soran
Digital lighting and bio-imaging are two emerging crucial research fields. Nanotechnology stands in the center of these applications by providing nano-scale particles possessing large surface-to-volume ratios, high effciency, and low toxicity while allowing for functionalization, effcient quality lighting and improved biocompatible bio-imaging. Some of the frequently employed nanoparticles in optoelectronics and imaging are colloidal semiconductor quantum dots, colloidal conjugated polymer nanoparticles, and colloidal iron oxide nanoparticles, all of which we have studied using colloidal approaches to make hybrid composites for lighting and imaging in this thesis. Fluorescent inorganic nanoparticles of colloidal quantum dots (QDs) attract significant interest for many optoelectronic and biomedical applications. Although they possess numerous advantages including broad absorption band, high quantum yield, and narrow emission spectrum, there are serious concerns on their recycling due to their cadmium-based composition. Alternatively, relatively low toxic organic uorescent polymer nanoparticles or oligomer nanoparticles have stepped forward. However, their reduced emission effciency and stability in solid state is an important limitation for their use in wide-spread solid-state lighting applications. To address these problems, in the first part of this thesis, we proposed and demonstrated the design of new hybrid composite material systems of oligomer nanoparticles to be used in solid-state lighting. We first showed that the emission effciency and stability of the oligomer nanoparticles in solid state are significantly improved based on our proposed crystallization technique. Here, using this simple and low-cost approach, oligomer nanoparticle monoliths were obtained from the powders of these crystals. Despite the disadvantages of using QDs, their high quantum effciency and narrow-band emission still make them a valuable asset for solid-state lighting. However, the decrease in solid-film effciencies is still an important issue to be addressed. With this perspective, in this thesis we utilized the incorporation of QDs into crystalline matrices allowing for the nonradiative energy transfer (NRET) to improve the emission capability of the nano-emitters. Since it is an interesting crystalline semiconductor organic molecule, we employed anthracene as the host donor medium and incorporated the quantum dots being exciton acceptors. Here, we systematically investigated the NRET from each anthracene emission peak to QDs and demonstrated the use of this composite system on LEDs as color converters and the polarization ratio change of quantum dots within this crystal system. Magnetic resonance imaging (MRI), for which we also developed colloidal contrast agents using nanoparticles (NPs) as the second part of this thesis, is a powerful diagnostic tool providing good soft tissue contrast and high spatial resolution. It produces T1- and T2-weighted images, in which the region of interest is observed as brighter and darker contrast, respectively. Superparamagnetic iron oxide (IO) NPs are an important member of T2-weighted contrast agents possessing low toxicity. However, they suer from poor anatomic details due to their darker contrast. Therefore, combining T1- and T2-weighted features in a single IO NP (dual-modal contrast) is a major step for improving MRI contrast. In order to meet the requirement for dual-modal contrast agents, which possess both T1- and T2-weighted imaging capability, in this thesis we synthesized highly monodisperse superparamagnetic cubic IO NPs. Magnetic characterizations along with in vivo MRI experiments demonstrated that these nanoparticles hold great promise for dual-modal imaging. This increased dual-modal eect without paramagnetic material doping or decreasing the size of nanoparticles smaller than 5 nm directed us to understand the relation of the T1 and T2 relaxations depending on the IO NP size and shape. Here, we showed the presence of intrinsic paramagnetic phase in magnetite IO NPs. Moreover, we demonstrated that this contribution is higher in IO NPs possessing cubic shape compared to the spherical counterparts, which explains the increased dual-modal effect in the monodisperse superparamagnetic nanocubes.
Open Access
Layer-by-layer self-assembled semiconductor nanocrystal composites with nonradiative resonance energy transfer for innovative architectural precise color tuning and control
(2009-08) Çiçek, Neslihan
In recent years semiconductor quantum dot nanocrystals (NC) have attracted significant interest and have found numerous important optoelectronic device applications mainly because of their highly tunable optical properties. For example, precisely tuning shades of color chromaticity is critically important in solid state lighting to achieve ultra-efficient, application-specific, spectrallyengineered illumination. To date such color tuning and control of NC emitters have been investigated and demonstrated only based on their composition, shape, and size (using the quantum confinement effect). All of these parameters are, however, limited to be controlled and set during the synthesis process. As a post-synthesis alternative, we proposed and demonstrated the precise and broad control and tuning of color chromaticity by strongly modifying photoluminescence decay kinetics of NC emitters solely based on nonradiative Förster resonance energy transfer (FRET) in layer-by-layer self-assembled NC composite structures. Locating NC emitters in such a layered architecture with a targeted gradient of bandgap in the close proximity (<10 nm) of each other and spatially interspacing them at the nanoscale (with a precision of <1 nm) enabled us to fine-tune and master FRET at a desired efficiency level of nonradiative energy transfer from electronically excited donor NCs to luminescent acceptor iv NCs. These proof-of-concept experimental demonstrations, combined with our numerical modeling and simulation results, proved a highly sensitive tuning capability based on FRET to span a broad color area in Commission Internationale De L’Eclairage (CIE) chromaticity diagram in principle beyond the limits of each of the commonly used LED epitaxial material systems. This innovative architectural tuning opens up a new direction for the photometric engineering of color-conversion LEDs.