Browsing by Author "Sharma, Manoj"

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Open Access
All-optical control of exciton flow in a colloidal quantum well complex
(Springer Nature, 2020) Yu, J.; Sharma, Manoj; Sharma, A.; Delikanlı, Savaş; Demir, Hilmi Volkan; Dang, C.
Excitonics, an alternative to romising for processing information since semiconductor electronics is rapidly approaching the end of Moore’s law. Currently, the development of excitonic devices, where exciton flow is controlled, is mainly focused on electric-field modulation or exciton polaritons in high-Q cavities. Here, we show an all-optical strategy to manipulate the exciton flow in a binary colloidal quantum well complex through mediation of the Förster resonance energy transfer (FRET) by stimulated emission. In the spontaneous emission regime, FRET naturally occurs between a donor and an acceptor. In contrast, upon stronger excitation, the ultrafast consumption of excitons by stimulated emission effectively engineers the excitonic flow from the donors to the acceptors. Specifically, the acceptors’ stimulated emission significantly accelerates the exciton flow, while the donors’ stimulated emission almost stops this process. On this basis, a FRET-coupled rate equation model is derived to understand the controllable exciton flow using the density of the excited donors and the unexcited acceptors. The results will provide an effective all-optical route for realizing excitonic devices under room temperature operation.
Open Access
Anomalous spectral characteristics of ultrathin sub-nm colloidal CdSe nanoplatelets
(Optical Society of America, 2017) Bose S.; Delikanlı, Savaş; Yeltik, Aydan; Sharma, Manoj; Erdem, Onur; Dang C.; Fan W.; Zhang D.H.; Demir, Hilmi Volkan
We demonstrate high quantum yield broad photoluminescence emission of ultrathin sub-nanometer CdSe nanoplatelets (two-monolayer). They also exhibit polarization-characterized lateral size dependent anomalous heavy hole and light/split-off hole absorption intensities. © 2017 IEEE.
Open Access
Cd-free Cu-doped ZnInS/ZnS Core/Shell nanocrystals: Controlled synthesis and photophysical properties
(SpringerOpen, 2018) Kaur, Manpreet; Sharma, Ashma; Olutaş, Murat; Erdem, Onur; Kumar, A.; Sharma, Manoj; Demir, Hilmi Volkan
Here, we report efficient composition-tunable Cu-doped ZnInS/ZnS (core and core/shell) colloidal nanocrystals (CNCs) synthesized by using a colloidal non-injection method. The initial precursors for the synthesis were used in oleate form rather than in powder form, resulting in a nearly defect-free photoluminescence (PL) emission. The change in Zn/In ratio tunes the percentage incorporation of Cu in CNCs. These highly monodisperse Cu-doped ZnInS CNCs having variable Zn/In ratios possess peak emission wavelength tunable from 550 to 650 nm in the visible spectrum. The quantum yield (QY) of these synthesized Cd-free CNCs increases from 6.0 to 65.0% after coating with a ZnS shell. The CNCs possessing emission from a mixed contribution of deep trap and dopant states to only dominant dopant-related Stokes-shifted emission are realized by a careful control of stoichiometric ratio of different reactant precursors during synthesis. The origin of this shift in emission was understood by using steady state and time-resolved fluorescence (TRF) spectroscopy studies. As a proof-of-concept demonstration, these blue excitable Cu-doped ZnInS/ZnS CNCs have been integrated with commercial blue LEDs to generate white-light emission (WLE). The suitable combination of these highly efficient doped CNCs results led to a Commission Internationale de l’Enclairage (CIE) color coordinates of (0.33, 0.31) at a color coordinate temperature (CCT) of 3694 K, with a luminous efficacy of optical radiation (LER) of 170 lm/Wopt and a color rendering index (CRI) of 88.
Open Access
CdSe/CdMnS nanoplatelets with bilayer core and magnetically doped shell exhibit switchable excitonic circular polarization: Implications for lasers and light-emitting diodes
(American Chemical Society, 2020-03) Najafi, A.; Tarasek, S.; Delikanlı, Savaş; Zhang, P.; Norden, T.; Shendre, S.; Sharma, Manoj; Bhattacharya, A.; Taghipour, Nima; Pientka, J.; Dedmir, Hilmi Volkan; Thomay, T.
We utilized time-resolved photoluminescence (TRPL) spectroscopy to study the excitonic circular polarization (PX) from CdSe/CdMnS core/shell nanoplatelets (NPLs) with a bilayer core. This allows an extensive study of the emission dynamics as a function of magnetic field, temperature, doping concentration, and excitation wavelength. In the presence of an external magnetic field, pulsed excitation below the shell gap results in near-zero excitonic circular polarization PX at all time delays. In contrast, pulsed excitation with photon energy larger than the shell gap results in a rapid (100 ps) buildup of the excitonic circular polarization which subsequently remains constant at a level of up to 40%. We propose a model to describe the dynamics which takes into account the exchange interaction between carrier and magnetic ion (Mn) spins. The studied system exhibits a fast switchable excitonic circular polarization, implying possible applications in lasers and light emitting diodes.
Open Access
Efficient generation of emissive many-body correlations in copper-doped colloidal quantum wells
(Cell Press, 2022-09-21) Yu, Junhong; Sharma, Manoj; Li, Mingjie; Liu, Baiquan; Hernández-Martínez, Pedro Ludwig; Delikanli, Savaş; Sharma, Ashma; Altintas, Yemliha; Hettiarachchi, Chathuranga; Sum, Tze Chien; Demir, Hilmi Volkan; Dang, Cuong
Colloidal quantum wells (CQWs) provide an appealing platform to achieve emissive many-body correlations for novel optoelectronic devices, given that they act as hosts for strong carrier Coulomb interactions and present suppressed Auger recombination. However, the demonstrated high-order excitonic emission in CQWs requires ultrafast pumping with high excitation levels and can only be spectrally resolved at the single-particle level under cryogenic conditions. Here, through systematic investigation using static power-dependent emission spectroscopy and transient carrier dynamics, we show that Cu-doped CdSe CQWs exhibit continuous-wave-pumped high-order excitonic emission at room temperature with a large binding energy of ∼64 meV. We attribute this unique behavior to dopant excitons in which the ultralong lifetime and the highly localized wavefunction facilitate the formation of many-body correlations. The spectrally resolved high-order excitonic emission generated at power levels compatible with solar irradiation and electrical injection might pave the way for novel solution-processed solid-state devices. © 2022 The Authors
Open Access
Light-Emitting diodes with Cu-Doped colloidal quantum wells: from ultrapure green, tunable dual-emission to white light
(WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2019) Liu, B.; Sharma, Manoj; Yu, J.; Shendre, S.; Hettiarachchi, C.; Sharma, Ashma; Yeltik, Aydan; Wang, L.; Sun, H.; Dang, C.; Demir, Hilmi Volkan
Copper‐doped colloidal quantum wells (Cu‐CQWs) are considered a new class of optoelectronic materials. To date, the electroluminescence (EL) property of Cu‐CQWs has not been revealed. Additionally, it is desirable to achieve ultrapure green, tunable dual‐emission and white light to satisfy the various requirement of display and lighting applications. Herein, light‐emitting diodes (LEDs) based on colloidal Cu‐CQWs are demonstrated. For the 0% Cu‐doped concentration, the LED exhibits Commission Internationale de L'Eclairage 1931 coordinates of (0.103, 0.797) with a narrow EL full‐wavelength at half‐maximum of 12 nm. For the 0.5% Cu‐doped concentration, a dual‐emission LED is realized. Remarkably, the dual emission can be tuned by manipulating the device engineering. Furthermore, at a high doping concentration of 2.4%, a white LED based on CQWs is developed. With the management of doping concentrations, the color tuning (green, dual‐emission to white) is shown. The findings not only show that LEDs with CQWs can exhibit polychromatic emission but also unlock a new direction to develop LEDs by exploiting 2D impurity‐doped CQWs that can be further extended to the application of other impurities (e.g., Mn, Ag).
Open Access
Light-induced paramagnetism in colloidal Ag+-doped CdSe nanoplatelets
(American Chemical Society, 2021-03-25) Najafi, A.; Sharma, Manoj; Delikanlı, Savaş; Bhattacharya, A.; Murphy, J. R.; Pientka, J.; Sharma, A.; Quinn, A. P.; Erdem, Onur; Kattel, S.; Kelestemur, Y.; Kovalenko, M. V.; Rice, W. D.; Demir, Hilmi Volkan; Petrou, A.
We describe a study of the magneto-optical properties of Ag+-doped CdSe colloidal nanoplatelets (NPLs) that were grown using a novel doping technique. In this work, we used magnetic circularly polarized luminescence and magnetic circular dichroism spectroscopy to study light-induced magnetism for the first time in 2D solution-processed structures doped with nominally nonmagnetic Ag+ impurities. The excitonic circular polarization (PX) and the exciton Zeeman splitting (ΔEZ) were recorded as a function of the magnetic field (B) and temperature (T). Both ΔEZ and PX have a Brillouin-function-like dependence on B and T, verifying the presence of paramagnetism in Ag+-doped CdSe NPLs. The observed light-induced magnetism is attributed to the transformation of nonmagnetic Ag+ ions into Ag2+, which have a nonzero magnetic moment. This work points to the possibility of incorporating these nanoplatelets into spintronic devices, in which light can be used to control the spin injection.
Open Access
Management of electroluminescence from silver-doped colloidal quantum well light-emitting diodes
(Cell Press, 2022-05-18) Liu, Baiquan; Sharma, Manoj; Yu, Junhong; Wang, Lin; Shendre, Sushant; Sharma, Ashma; Izmir, Merve; Delikanlı, Savaş; Altıntaş, Yemliha; Dang, Cuong; Sun, Handong; Demir, Hilmi Volkan
Impurity doping is a promising strategy to afford colloidal nanocrystals exhibiting novel optical, catalytic, and electronic characteristics. However, some significant properties of noble metal-doped nanocrystals (NMD-NCs) remain unknown. Here, we report the electroluminescence (EL) from NMD-NCs. By doping silver impurity into cadmium selenide colloidal quantum wells (CQWs), dual-emission emitters are achieved and a light-emitting diode (LED) with a luminance of 1,339 cd m−2 is reported. In addition, the proposed energy gap engineering to manage exciton recombination is a feasible scheme for tunable EL emissions (e.g., the dopant emission is tuned from 606 to 761 nm). Furthermore, an organic-inorganic hybrid white LED based on CQWs is realized, reaching a color rendering index of 82. Moreover, flexible CQW-LEDs are reported. The findings present a step to unveil the EL property of NMD-NCs, which can be extended to other noble metal impurities, and pave the pathway for NMD-NCs as a class of electronic materials for EL applications. © 2022 The Authors
Open Access
Modulating emission properties in a host–guest colloidal quantum well superlattice
(Wiley-VCH Verlag GmbH & Co. KGaA, 2021-12-19) Yu, J.; Sharma, Manoj; Wang, Y.; Delikanlı, S.; Baruj, Hamed Dehghanpour; Sharma, A.; Demir, Hilmi Volkan
Self-assembly of colloidal nanocrystals into ordered superlattices is a powerful approach to enable novel collective properties which are not available in individual colloids. However, to date, it remains a major challenge to develop a practical route to modulate such collective properties for potential photonic applications. Herein, it is shown that the collective emission properties in colloidal quantum well (CQW) superlattices, including emission color and anisotropy, can be effectively modulated in a binary host–guest architecture. The experimental and theoretical results reveal that excitons of the host (i.e., the undoped CQWs) generated by photoexcitation can be controllably harvested by the guest (i.e., the Cu-doped CQWs) for light emission, owing to an exciton hopping assisted exciton trapping process. Such a nano-building block with tunable collective optical properties may enlighten novel colloidal material-based photonic applications, including optical anti-counterfeiting, next-generation liquid crystal displays, and multifunctional biological markers.
Open Access
Mutual energy transfer in a binary colloidal quantum well complex
(American Chemical Society, 2019) Yu, J.; Sharma, Manoj; Delikanlı, Savaş; Birowosuto, M. D.; Demir, Hilmi Volkan; Dang, C.
Förster resonance energy transfer (FRET) is a fundamental process that is key to optical biosensing, photosynthetic light harvesting, and down-converted light emission. However, in total, conventional FRET in a donor–acceptor pair is essentially unidirectional, which impedes practical application of FRET-based technologies. Here, we propose a mutual FRET scheme that is uniquely bidirectional in a binary colloidal quantum well (CQW) complex enabled by utilizing the d orbital electrons in a dopant–host CQW system. Steady-state emission intensity, time-resolved, and photoluminescence excitation spectroscopies have demonstrated that two distinct CQWs play the role of donor and acceptor simultaneously in this complex consisting of 3 monolayer (ML) copper-doped CQWs and 4 ML undoped CQWs. Band-edge excitons in 3 ML CQWs effectively transfer the excitation to excitons in 4 ML CQWs, whose energy is also harvested backward by the dopants in 3 ML CQWs. This binary CQW complex, which offers a unique mutual energy-transfer mechanism, may unlock revolutionary FRET-based technologies.
Open Access
Near-infrared emission from CdSe-Based nanoplatelets induced by Ytterbium doping
(American Chemical Society, 2023-02-15) İzmir, Merve; Durmusoglu, Emek G.; Sharma, Manoj; Shabani, Farzan; Işık, Furkan; Delikanlı, Savaş; Sharma, Vijay Kumar; Demir, Hilmi Volkan
Cadmium selenide (CdSe) nanoplatelets (NPLs) have attracted significant attention thanks to their favorable optical properties, including narrow emission linewidths, reduced Auger recombination, and a high absorption cross section. However, the photoluminescence (PL) quantum yield (QY) in the near-infrared (NIR) region is poor as compared to that in the visible region. Doping of metal ions is proven to be a successful strategy for inducing Stokes-shifted NIR emission. Here, we report the first account of the successful doping of ytterbium (Yb) into CdSe NPLs by a modified seeded-growth method. The successful incorporation of divalent Yb ions into CdSe NPLs resulted in an additional NIR emission apart from their excitonic emission. By optimizing the dopant concentration, we observed an impressive PL QY of ∼55% for these Yb-doped NPLs. Detailed elemental and optical characterizations were conducted to understand the emerging photophysical properties of these Yb-doped NPLs. These NIR-emitting lanthanide-doped CdSe NPLs might have applications in the next-generation bioimaging, night vision, and photodetection. © 2023 The Authors. Published by American Chemical Society
Open Access
Near-Infrared-Emitting five-monolayer thick copper-doped CdSe nanoplatelets
(WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2019) Sharma, Ashma; Sharma, Manoj; Güngör, Kıvanç; Olutaş, Murat; Dede, Didem; Demir, Hilmi Volkan
Doped nanocrystals are instrumental to the high‐performance luminescent solar concentrators (LSCs) and the color conversion devices. Recently, copper (Cu)‐doped three and four monolayer (ML) thick CdSe nanoplatelets (NPLs) have been shown superior to the existing Cu‐doped quantum dots (QDs) for their use in LSCs. However, additional improvement in the LSC performance can be achieved by further redshifting the emission into the near‐infrared (NIR) region of electromagnetic spectrum and increasing the absorbed portion of the solar irradiation. Cu‐doping into higher thicknesses of these atomically flat NPLs (e.g., ≥5 ML) can achieve these overarching goals. However, addition of the dopant ions during the nucleation stage disturbs this high‐temperature growth process and leads to multiple populations of NPLs and QDs. Here, by carefully controlling the precursor chemistry the successful doping of Cu in five ML thick NPLs by high‐temperature nucleation doping method is demonstrated. The optimized synthesis method shows nearly pure population of doped five ML thick NPLs, which possess ≈150 nm Stokes‐shifted NIR emission with high quantum yield of 65 ± 2%. Structural, elemental, and optical studies are conducted to confirm the successful doping and understand the detailed photophysics. Finally, these materials are tested experimentally and theoretically for their performance as promising LSC materials.
Open Access
Nonradiative energy transfer between doped and undoped flat semiconductor nanocrystals of colloidal Quasi-2D nanoplatelets
(American Chemical Society, 2019) Yeltik, Aydan; Olutaş, Murat; Sharma, Manoj; Güngör, Kıvaç; Demir, Hilmi Volkan
Atomically flat colloidal semiconductors such as nanoplatelets (NPLs) promise great potential for different optoelectronic applications. Here, we systematically investigate the excitonic energy transfer from colloidal Cu-doped CdSe to undoped core/shell CdSe/CdS nanoplatelets via steady-state and time-resolved photoluminescence spectroscopy techniques. We show the strong quenching in photoluminescence emission of the doped NPL donors together with significant modifications in the time-resolved kinetics by changing the concentration of the undoped NPL acceptors in close proximity. This newly presented all-colloidal and all-quasi2D doped−undoped NPL−NPL hybrid system shows near-unity room-temperature energy transfer efficiency (99%) in solid films. We strongly believe that such highly efficient energy transfer in doped−undoped hybrid films will create more interest in the scientific community to further explore different donor/acceptor combinations with these newly reported doped NPLs for next-generation energy harvesting applications.
Open Access
Persuasive evidence for electron–nuclear coupling in diluted magnetic colloidal nanoplatelets using optically detected magnetic resonance spectroscopy
(American Chemical Society, 2019) Strassberg, R.; Delikanlı, Savaş; Barak, Y.; Dehnel, J.; Kostadinov, A.; Maikov, G.; Hernandez-Martinez, P. L.; Sharma, Manoj; Demir, Hilmi Volkan; Lifshitz, E.
The incorporation of magnetic impurities into semiconductor nanocrystals with size confinement promotes enhanced spin exchange interaction between photogenerated carriers and the guest spins. This interaction stimulates new magneto-optical properties with significant advantages for emerging spin-based technologies. Here we observe and elaborate on carrier–guest interactions in magnetically doped colloidal nanoplatelets with the chemical formula CdSe/Cd1–xMnxS, explored by optically detected magnetic resonance and magneto-photoluminescence spectroscopy. The host matrix, with a quasi-type II electronic configuration, introduces a dominant interaction between a photogenerated electron and a magnetic dopant. Furthermore, the data convincingly presents the interaction between an electron and nuclear spins of the doped ions located at neighboring surroundings, with consequent influence on the carrier’s spin relaxation time. The nuclear spin contribution by the magnetic dopants in colloidal nanoplatelets is considered here for the first time.
Open Access
Record high external quantum efficiency of 19.2% achieved in light-emitting diodes of colloidal quantum wells enabled by hot-Injection shell growth
(WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2020) Liu, B.; Altıntaş, Yemliha; Wang, L.; Shendre, S.; Sharma, Manoj; Sun, H.; Mutlugün, Evren; Demir, Hilmi Volkan
Colloidal quantum wells (CQWs) are regarded as a highly promising class of optoelectronic materials, thanks to their unique excitonic characteristics of high extinction coefficients and ultranarrow emission bandwidths. Although the exploration of CQWs in light‐emitting diodes (LEDs) is impressive, the performance of CQW‐LEDs lags far behind other types of soft‐material LEDs (e.g., organic LEDs, colloidal‐quantum‐dot LEDs, and perovskite LEDs). Herein, high‐efficiency CQW‐LEDs reaching close to the theoretical limit are reported. A key factor for this high performance is the exploitation of hot‐injection shell (HIS) growth of CQWs, which enables a near‐unity photoluminescence quantum yield (PLQY), reduces nonradiative channels, ensures smooth films, and enhances the stability. Remarkably, the PLQY remains 95% in solution and 87% in film despite rigorous cleaning. Through systematically understanding their shape‐, composition‐, and device‐engineering, the CQW‐LEDs using CdSe/Cd0.25Zn0.75S core/HIS CQWs exhibit a maximum external quantum efficiency of 19.2%. Additionally, a high luminance of 23 490 cd m−2, extremely saturated red color with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.715, 0.283), and stable emission are obtained. The findings indicate that HIS‐grown CQWs enable high‐performance solution‐processed LEDs, which may pave the path for future CQW‐based display and lighting technologies.
Open Access
sp-d exchange interactions in wave function engineered colloidal CdSe/Mn: CdS Hetero-Nanoplatelets
(American Chemical Society, 2018) Muckel, F.; Delikanlı S.; Hernández-Martínez, Pedro Ludwig; Priesner, T.; Lorenz, S.; Ackermann, J.; Sharma, Manoj; Demir, Hilmi Volkan; Bacher, G.
In two-dimensional (2D) colloidal semiconductor nanoplatelets, which are atomically flat nanocrystals, the precise control of thickness and composition on the atomic scale allows for the synthesis of heterostructures with well-defined electron and hole wave function distributions. Introducing transition metal dopants with a monolayer precision enables tailored magnetic exchange interactions between dopants and band states. Here, we use the absorption based technique of magnetic circular dichroism (MCD) to directly prove the exchange coupling of magnetic dopants with the band charge carriers in hetero-nanoplatelets with CdSe core and manganese-doped CdS shell (CdSe/Mn:CdS). We show that the strength of both the electron as well as the hole exchange interactions with the dopants can be tuned by varying the nanoplatelets architecture with monolayer accuracy. As MCD is highly sensitive for excitonic resonances, excited level spectroscopy allows us to resolve and identify, in combination with wave function calculations, several excited state transitions including spin-orbit split-off excitonic contributions. Thus, our study not only demonstrates the possibility to expand the extraordinary physical properties of colloidal nanoplatelets toward magneto-optical functionality by transition metal doping but also provides an insight into the excited state electronic structure in this novel two-dimensional material.
Open Access
Spectrally wide-range-tunable, efficient, and bright colloidal light-emitting diodes of quasi-2D nanoplatelets enabled by engineered alloyed heterostructures
(American Chemical Society, 2020) Altıntaş, Yemliha; Liu, B.; Hernández-Martínez, P. L.; Gheshlaghi, Negar; Shabani, Farzan; Sharma, Manoj; Wang, L.; Sun, H.; Mutlugün, Evren; Demir, Hilmi Volkan
Recently, there has been tremendous interest in the synthesis and optoelectronic applications of quasi-two-dimensional colloidal nanoplatelets (NPLs). Thanks to the ultranarrow emission linewidth, high-extinction coefficient, and high photostability, NPLs offer an exciting opportunity for high-performance optoelectronics. However, until now, the applications of these NPLs are limited to available discrete emission ranges, limiting the full potential of these exotic materials as efficient light emitters. Here, we introduce a detailed systematic study on the synthesis of NPLs based on the alloying mechanisms in core/shell, core/alloyed shell, alloyed core/shell, and alloyed core/alloyed shell heterostructures. Through the engineering of the band gap supported by the theoretical calculations, we carefully designed and successfully synthesized the NPL emitters with continuously tunable emission. Unlike conventional NPLs showing discrete emission, here, we present highly efficient core/shell NPLs with fine spectral tunability from green to deep-red spectra. As an important demonstration of these efficient emitters, the first-time implementation of yellow NPL light-emitting diodes (LEDs) has been reported with record device performance, including the current efficiency surpassing 18.2 cd A–1, power efficiency reaching 14.8 lm W–1, and record luminance exceeding 46 900 cd m–2. This fine and wide-range color tunability in the visible range from stable and efficient core/shell NPLs is expected to be extremely important for the optoelectronic applications of the family of colloidal NPL emitters.
Open Access
Strong plasmon-wannier mott exciton interaction with high aspect ratio colloidal quantum wells
(Cell Press, 2020) Yu, J.; Hou, S.; Sharma, Manoj; Tobing, L. Y. M.; Song, Z.; Delikanlı, Savaş; Hettiarachchi, C.; Zhang, D.; Fan, W.; Birowosuto, M. D.; Wang, H.; Demir, Hilmi Volkan; Dang, C.
The strong interaction between excitons and plasmons, manifested as Rabi splitting of the eigen energies, is of fundamental interest for manipulating photons in nanoscale devices. Thanks to their enhanced photostability and minimal inhomogeneous broadening compared with organic molecules, inorganic emitters are preferred for practical applications. However, a relatively small Rabi splitting with inorganic materials severely hinders the active plasmonic operation, considering its weak optical nonlinearity and slow energy interexchange. Here, we circumvent this problem in a hybrid system consisting of high aspect ratio colloidal quantum wells (HARCQWs) and an individual plasmonic silver nanocube. By taking advantages of a highly in-plane oriented exciton, enhanced exciton binding energy, and non-stacking properties in HARCQWs, we demonstrate an unprecedented giant Rabi splitting energy up to 400 meV under ambient conditions, which is observed not only in scattering but also in photoluminescent spectra. These findings are a key step toward achieving inorganic plasmonic devices.
Open Access
Synthesis and characterization of Mn doped ZnCdS core shell nanostructures QDs using a chemical precipitation route
(AIP, 2016) Kaur, M.; Pandey, O. P.; Sharma, Manoj
With advancement in time, researchers has drawn great attention in the synthesis and characterization of mono dispersed alloyed nanocomposites of II-VI compounds. Ternary semiconductor alloyed ZnCdS quantum dots (QD's) exhibit properties intermediate between those of ZnS and CdS. It shows high absorption coefficients, a composition tunable and size tunable band gap. Moreover, ZnCdS alloyed NC's display unique composition dependent properties distinct from those of their bulk counterparts. The most striking feature of the alloyed NC's nanocrystals is their unusual long time stability in emission wavelength. ZnCdS alloyed QD's at room temperature has been synthesized using chemical precipitation method. Undoped and Mn2+ doped ZnCdS QDs have been synthesized and studied. UV-visible absorption spectrum shows absorbance in the visible region and photoluminescence (PL) emission spectra of the doped ZnCdS QD's shows orange emission in comparison to weak blue emission from undoped QDs. The crystallite size is calculated from the XRD patterns. The experimental results indicate that this easy synthesis route would prove a versatile approach for the preparation of doped and undoped ZnCdS QD's.
Open Access
Two-dimensional CdSe-based nanoplatelets: their heterostructures, doping, photophysical properties, and applications
(Institute of Electrical and Electronics Engineers, 2020) Sharma, Manoj; Delikanlı, Savaş; Demir, Hilmi Volkan
In the past decade, colloidal quantum wells, also known as 2-D semiconductor nanoplatelets (NPLs), have been added to the colloidal nanocrystal (NC) family. Through the unique control of the thickness with monolayer precision, these novel materials exhibit strong 1-D quantum confinement that offers unique optical properties along with the possibility of fabricating advanced heterostructures, which are not possible with other quantum-confined nanostructures. The 2-D CdX (X = Se, S)-based NPLs provide high color purities, fast fluorescence lifetimes, and large exciton binding energies. This review covers the latest developments in the successful utilization of these flat NCs in different nanophotonic device applications. The synthesis of the advanced heterostructures of flat 2-D NCs (e.g., core-shell, core-crown, and core-crown-shell) has matured very rapidly, and new exciting optical and electronic applications are emerging. Doping of these atomically thin NCs also offers new possibilities for their utilization in different solar light harvesting, magnetic, electronic, and lasing applications. This review also includes the recent advancements in the understanding of their unique optical properties that are of utmost importance for their practical implementation in light-emitting devices and lasers. Finally, we present a future perspective on their successful utilization in different nanophotonic applications.