Journal articles: 'Electronic Properties - Semiconductor Nanocrystals (NCs)'

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Qiao, Fen. "Semiconductor Nanocrystals for Photovoltaic Devices." Materials Science Forum 852 (April 2016): 935–38. http://dx.doi.org/10.4028/www.scientific.net/msf.852.935.

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Recently, photovoltaic devices based on colloidal semiconductor nanocrystals (NCs) have attracted a great interest due to their flexible synthesis with tunable band gaps and shape-dependent optical and electronic properties. However, the surface of NCs typically presents long chain with electrically insulating organic ligands, which hinder the device applications for NCs. So the major challenge of NCs for photovoltaic devices application is to decrease the inter NC space and the height of the tunnel barriers among NCs, therefore increase the transport properties of NCs. In this article, recent development of colloidal semiconductor NCs and possible routes for improving transport properties of colloidal NCs were reviewed. Among those methods, the thermal annealing approach provides a simple and cost-effective way to fabricate superlattice and to decrease the inter-space among NCs, which may be used for the preparation of other nanocrystalline superstructure and functional devices.

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Kovalenko, Maksym V., Loredana Protesescu, and Maryna I. Bodnarchuk. "Properties and potential optoelectronic applications of lead halide perovskite nanocrystals." Science 358, no. 6364 (November 9, 2017): 745–50. http://dx.doi.org/10.1126/science.aam7093.

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Semiconducting lead halide perovskites (LHPs) have not only become prominent thin-film absorber materials in photovoltaics but have also proven to be disruptive in the field of colloidal semiconductor nanocrystals (NCs). The most important feature of LHP NCs is their so-called defect-tolerance—the apparently benign nature of structural defects, highly abundant in these compounds, with respect to optical and electronic properties. Here, we review the important differences that exist in the chemistry and physics of LHP NCs as compared with more conventional, tetrahedrally bonded, elemental, and binary semiconductor NCs (such as silicon, germanium, cadmium selenide, gallium arsenide, and indium phosphide). We survey the prospects of LHP NCs for optoelectronic applications such as in television displays, light-emitting devices, and solar cells, emphasizing the practical hurdles that remain to be overcome.

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Harfenist, S. A., Z. L. Wang, T. G. Schaaff, and R. L. Whettent. "A BCC Superlattice of Passivated Gold Nanocrystals." Microscopy and Microanalysis 4, S2 (July 1998): 716–17. http://dx.doi.org/10.1017/s1431927600023709.

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A recent development in the study of nanocrystalline materials has been the self-assembly of passivated nanometer scale building blocks into larger, well ordered structures reaching the micron scale. Nanocrystal supercrystals (NCS) have been observed in metallic, semiconductor, and magnetic materials. In most cases the nanocrystals (NXs) are encapsulated in some inert medium that effectively protects the nanocrystal core and its unique electronic and optical properties. Here we describe the self-assembly of gold nanocrystals (∼4.5 nm core diameter), passivated with hexanethiol self-assembled-monolayers into ordered regions exhibiting a body-centered-cubic (bcc) superstructure. Transmission Electron Microscopy (TEM) imaging and Electron Diffraction (ED) experiments were used to characterize the NCSs and their resulting superstructures.A large agglomeration of NCSs can be seen in figure 1. One can clearly see regions of periodicity within the nanocrystal aggregation.

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Sayevich, Vladimir, Chris Guhrenz, and Nikolai Gaponik. "All-Inorganic and Hybrid Capping of Nanocrystals as Key to Their Application-Relevant Processing." MRS Advances 3, no. 47-48 (2018): 2923–30. http://dx.doi.org/10.1557/adv.2018.445.

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AbstractThe design of the surface chemistry of colloidal semiconductor nanocrystals (NCs) presents a powerful synthetic approach that allows to tune the optical and electronic properties of the particles in independent and precisely desired manner, to provide chemical and colloidal stability in diverse media, and, finally, to control their targeted applicability ranging from catalysis, medicine to advanced electronic devices. In this article, we summarize the successful functionalization of colloidal NCs with specifically chosen ligands using a novel ligand-exchange strategy. To transform diverse colloidal NCs into a competitive class of solution-processed semiconductors for electronic applications, we replaced the pristine, insulating ligands with tiny inorganic and hybrid inorganic/organic species. The surface modification with inorganic ions modulates the charge carrier density in NC units and guarantees enhanced interparticle interactions. The subsequent functionalization of the all-inorganic-capped NCs with organic molecules leads to the formation of hybrid inorganic/organic-capped NCs. For example, the introduction of short amine molecules enables to preserve the optical and electronic characteristics of their all-inorganic counterparts, while extending the solubility range and improving the ability to form long-range ordered 2D and 3D superstructures. Moreover, these short amines can be further used as convenient axillary co-ligands facilitating the surface functionalization of all-inorganic NCs with other biocompatible molecules, such as polyethylene glycol (PEG). This opens further perspectives for NCs not only in optoelectronic but also in biological and medical applications.

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Casanova-Cháfer, Juan, Rocío García-Aboal, Pedro Atienzar, and Eduard Llobet. "Gas Sensing Properties of Perovskite Decorated Graphene at Room Temperature." Sensors 19, no. 20 (October 20, 2019): 4563. http://dx.doi.org/10.3390/s19204563.

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This paper explores the gas sensing properties of graphene nanolayers decorated with lead halide perovskite (CH3NH3PbBr3) nanocrystals to detect toxic gases such as ammonia (NH3) and nitrogen dioxide (NO2). A chemical-sensitive semiconductor film based on graphene has been achieved, being decorated with CH3NH3PbBr3 perovskite (MAPbBr3) nanocrystals (NCs) synthesized, and characterized by several techniques, such as field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Reversible responses were obtained towards NO2 and NH3 at room temperature, demonstrating an enhanced sensitivity when the graphene is decorated by MAPbBr3 NCs. Furthermore, the effect of ambient moisture was extensively studied, showing that the use of perovskite NCs in gas sensors can become a promising alternative to other gas sensitive materials, due to the protective character of graphene, resulting from its high hydrophobicity. Besides, a gas sensing mechanism is proposed to understand the effects of MAPbBr3 sensing properties.

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Qiao, Fen, Qian Wang, Zixia He, Qing Liu, and Aimin Liu. "Self-Assembly of Colloidal Nanorods Arrays." International Journal of Nanoscience 14, no. 01n02 (February 2015): 1460029. http://dx.doi.org/10.1142/s0219581x14600291.

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Recently, self-assembly of colloidal semiconductor nanocrystals (NCs) have attracted a great interest due to their flexible synthesis with tunable band gaps and shape-dependent optical and electronic properties. In particular, nanorods (NRs) superlattice is receiving considerable attention. Typically, the NRs superlattice is prepared by guiding the process of self-assembly through external forces. In this article, recent development of self-assembly approaches at work in fabricating NRs superlattices was reviewed. Despite those effective self-assembly techniques through external controls to obtain NCs assemblies during deposition were widespread used. But these techniques are time consuming, and cannot get rid of the organic capping insulated molecules surrounding the NCs. So there is still a challenge to guarantee the electron/hole dissociation as well as the charge transport of NCs. Here, thermal annealing method that applies selectivity even in the presence of organic molecules will be adopted to obtain colloidal NRs superlattices, and the self-assembly mechanism of NRs were briefly addressed.

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Dzhagan, Volodymyr, Olga Kapush, Nazar Mazur, Yevhenii Havryliuk, Mykola I. Danylenko, Serhiy Budzulyak, Volodymyr Yukhymchuk, Mykhailo Valakh, Alexander P. Litvinchuk, and Dietrich R. T. Zahn. "Colloidal Cu-Zn-Sn-Te Nanocrystals: Aqueous Synthesis and Raman Spectroscopy Study." Nanomaterials 11, no. 11 (October 31, 2021): 2923. http://dx.doi.org/10.3390/nano11112923.

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Cu-Zn-Sn-Te (CZTTe) is an inexpensive quaternary semiconductor that has not been investigated so far, unlike its intensively studied CZTS and CZTSe counterparts, although it may potentially have desirable properties for solar energy conversion, thermoelectric, and other applications. Here, we report on the synthesis of CZTTe nanocrystals (NCs) via an original low-cost, low-temperature colloidal synthesis in water, using a small-molecule stabilizer, thioglycolic acid. The absorption edge at about 0.8–0.9 eV agrees well with the value expected for Cu2ZnSnTe4, thus suggesting CZTTe to be an affordable alternative for IR photodetectors and solar cells. As the main method of structural characterization multi-wavelength resonant Raman spectroscopy was used complemented by TEM, XRD, XPS as well as UV-vis and IR absorption spectroscopy. The experimental study is supported by first principles density functional calculations of the electronic structure and phonon spectra. Even though the composition of NCs exhibits a noticeable deviation from the Cu2ZnSnTe4 stoichiometry, a common feature of multinary NCs synthesized in water, the Raman spectra reveal very small widths of the main phonon peak and also multi-phonon scattering processes up to the fourth order. These factors imply a very good crystallinity of the NCs, which is further confirmed by high-resolution TEM.

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Anni, Marco. "Polymer-II-VI Nanocrystals Blends: Basic Physics and Device Applications to Lasers and LEDs." Nanomaterials 9, no. 7 (July 19, 2019): 1036. http://dx.doi.org/10.3390/nano9071036.

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Hybrid thin films that combine organic conjugated molecules and semiconductors nanocrystals (NCs) have been deeply investigated in the previous years, due to their capability to provide an extremely broad tuning of their electronic and optical properties. In this paper we review the main aspects of the basic physics of the organic–inorganic interaction and the actual state of the art of lasers and light emitting diodes based on hybrid active materials.

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Camellini, Andrea, Haiguang Zhao, Sergio Brovelli, Ranjani Viswanatha, Alberto Vomiero, and Margherita Zavelani-Rossi. "(Invited) Ultrafast Spectroscopy in Semiconductor Nanocrystals: Revealing the Origin of Single Vs Double Emission, of Optical Gain and the Role of Dopants." ECS Meeting Abstracts MA2022-01, no. 20 (July 7, 2022): 1104. http://dx.doi.org/10.1149/ma2022-01201104mtgabs.

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A wide variety of materials with nanometre dimensions are increasingly explored for photonic applications. Among them, semiconductor nanocrystals (NCs) are very promising for a variety of uses, including light emission devices (LEDs), lasers, detectors, photovoltaic cells, biological labelling and sensing [1]. Key advantage of NCs is the possibility to tailor their optical response by controlling the electronic structure (“wave function engineering”) through the choice of composition, size and shape. Significant and interesting results have been obtained with heterostructured and doped NCs. Beyond single wavelength tuneable band-edge emission, other regimes have been demonstrated such as intragap emission, simultaneous emission on two different wavelengths, amplified spontaneous emission and laser emission. The luminescent properties are governed by exciton decay, which can proceed through radiative or nonradiative pathways, following different routes. The study of exciton dynamics can allow elucidating the processes connected to single or dual emission and to optical gain. This, in turn, can lead to the identification of the functional and structural characteristics that are responsible for these behaviors. Exciton relaxation occurs on picosecond timescales, so ultrafast optical techniques are required to perform these studies. In this talk, we present studies carried out by ultrafast pump-probe spectroscopy technique, with 100-fs time resolution, on CdSe/CdS and PbS/CdS heterostructured NCs, with different geometries (core/shell, dot-in-rod, dot-in-bulk, with sharp or graded interface) [2-6] and CdSeS and CdZnSe doped NCs [7,8]. These NCs are optically active in the visible and near-infrared spectral region, show single and dual colour photoluminescence emission, optical gain, laser emission and intragap emission [2-9]. The analysis of the experimental data allowed us to unravel the decay processes: the initials take place in a few ps, leading to the ultimate emitting state whose lifetime can extend to hundreds of ps to few ns, allowing for efficient luminescence and optical gain. Our data on heterostructures allowed us to clarify the role of the volume and of the shape of the outer component and the effect of the interface [2-4]. We found that dual emission is possible for both thick and thin quantum-confined shells, and for different interfaces. We studied the decoupling of excitons lying in the two different component of the NC (core exciton and shell exciton) and we revealed the evolution of the exciton barrier known as dynamic hole-blockade effect. We showed that these phenomena are strictly connected to dual emission and optical gain and we identified the condition for their maximum efficiency, in term of band alignment and band transitions. Our results provide a comprehensive understanding of the physical phenomena governing dual-emission mechanisms, suppression of Auger recombination, optical gain and laser emission in heterostructured NCs. Experiments on CdZnSe NCs doped with Mn and on CdSeS NCs engineered with sulfur vacancies, enabled us to disclose donor and acceptor localized states in the band gap. We observed the carrier dynamics responsible for intragap emission which is associated to the emergence of a transient Mn3+ state [7], in the first case, and to a donor state below the conduction band introduced by sulfur vacancies [8], in the latter case. In conclusion, the study of the exciton dynamics in different NCs allowed us to elucidate the relation between structural-morphological characteristics (shape, volume, and interface) and unconventional emission capabilities (dual emission and optical gain) in heterostructures and the photophysics of electronic states introduced by doping. This knowledge is very important to control NC functionalities toward new multilevel electronic or photonic schemes and in applications such as lasers [9], photoelectrochemical (PEC) cell [10], white light emission [11], ratiometric sensing [12]. [1] P. V. Kamat and G. D. Scholes, J. Phys. Chem. Lett. 7, 584 (2016) [2] G. Sirigu et al., Phys. Rev. B 96, 155303 (2017) [3] V. Pinchetti et al., ACS Nano 10, 6877-6887 (2016) [4] H. Zhao et al., Nanoscale 8, 4217-4226 (2016) [5] M. Zavelani-Rossi et al., Nano Lett. 10, 3142-3150 (2010) [6] R. Krahne et al., Appl. Phys. Lett. 98, 063105 (2011) [7] K. Gahlot et al., ACS Energy Lett. 4, 729−735 (2019) [8] F. Carulli et al., Nano Lett. 21, 6211−6219 (2021) [9] M. Zavelani-Rossi et al., Laser & Photonics Reviews 6, 678-683 (2012) [10] L. Jin et al., Nano Energy 30, 531-541 (2016) [11] S. Sapra et al., Adv. Mater. 19, 569 (2007) [12] J. Liu et al., ACS Photonics, 2479 (2019)

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Deng, Yuan, Yicheng Zeng, Wanying Gu, Pan Huang, Geyu Jin, Fangze Liu, Jing Wei, and Hongbo Li. "Colloidal Synthesis and Ultraviolet Luminescence of Rb2AgI3 Nanocrystals." Crystals 13, no. 7 (July 16, 2023): 1110. http://dx.doi.org/10.3390/cryst13071110.

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Semiconductor nanocrystals (NCs) hold immense potential as luminescent materials for various optoelectronic applications. While significant progress has been made in developing NCs with outstanding optical properties in the visible range, their counterparts emitting in the ultraviolet (UV) spectrum are less developed. Rb2AgI3 is a promising UV-emitting material due to its large band gap and high stability. However, the optical properties of low-dimensional Rb2AgI3 NCs are yet to be thoroughly explored. Here, we synthesized Rb2AgI3 NCs via a hot injection method and investigated their properties. Remarkably, these NCs exhibit UV luminescence at 302 nm owing to self-trapped excitons. The wide-bandgap nature of Rb2AgI3 NCs, combined with their intrinsic UV luminescence, offers considerable potential for applications in UV photonic nanodevices. Our findings contribute to the understanding of Rb2AgI3 NCs and pave the way for exploiting their unique properties in advanced optoelectronic systems.

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Cheng, Oscar Hsu-Cheng, Tian Qiao, Matthew Sheldon, and Dong Hee Son. "Size- and temperature-dependent photoluminescence spectra of strongly confined CsPbBr3 quantum dots." Nanoscale 12, no. 24 (2020): 13113–18. http://dx.doi.org/10.1039/d0nr02711a.

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Lead-halide perovskite nanocrystals (NCs) are receiving much attention as a potential high-quality source of photons due to their superior luminescence properties in comparison to other semiconductor NCs.

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Frolova, Elena, Tobias Otto, Nikolai Gaponik, and Vladimir Lesnyak. "Incorporation of CdTe Nanocrystals into Metal Oxide Matrices Towards Inorganic Nanocomposite Materials." Zeitschrift für Physikalische Chemie 232, no. 9-11 (August 28, 2018): 1335–52. http://dx.doi.org/10.1515/zpch-2018-1139.

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Abstract In this work we present a technique of incorporation of semiconductor CdTe nanocrystals (NCs) into metal oxide matrices prepared by inorganic sol-gel method. As the matrices, we chose alumina and aluminum tin oxide, which are optically transparent in the visible region. Among them the first is electrically insulating, while the second is conductive and thus can be used in optoelectronic devices. We found optimal synthetic parameters allowing us to maintain optical properties of the NCs in both matrices even after heating up to 150°C in air. Therefore, in our approach we overcame a common problem of degradation of the optical properties of semiconductor NCs in oxide matrices as a result of the incorporation and subsequent interaction with the matrix. The resulting materials were characterized in detail from the point of view of their optical and structural properties. Based on the results obtained, we suggest the formation mechanism of these materials. Semiconductor NCs embedded in robust and optically transparent metal oxides offer promising applications in optical switching, optical filtering, waveguides, light emitting diodes, and solar concentrators.

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Slyusarenko, Nina, Marina Gerasimova, Alexei Plotnikov, Nikolai Gaponik, and Evgenia Slyusareva. "Photoluminescence properties of self-assembled chitosan-based composites containing semiconductor nanocrystals." Physical Chemistry Chemical Physics 21, no. 9 (2019): 4831–38. http://dx.doi.org/10.1039/c8cp07051b.

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The photoluminescence (PL) properties of composites obtained by embedding green-emitting semiconductor nanocrystals (NCs) of two different types (thiol-capped CdTe and CdSe/ZnS) into chitosan-based biopolymer particles were investigated.

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Ashkenazi, Or, Doron Azulay, Isaac Balberg, Shinya Kano, Hiroshi Sugimoto, Minoru Fujii, and Oded Millo. "Size-dependent donor and acceptor states in codoped Si nanocrystals studied by scanning tunneling spectroscopy." Nanoscale 9, no. 45 (2017): 17884–92. http://dx.doi.org/10.1039/c7nr06257e.

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SHEN, QI-HUI, YAN LIU, XI YU, XIAO-YANG LIU, MING-QIANG ZOU, JIN-FENG LI, and JIAN-GUANG ZHOU. "FORMATION OF II–VI SEMICONDUCTOR NANOCRYSTALS WITH TUNABLE VISIBLE EMISSION IN AQUEOUS SOLUTION PROMOTED BY HYDRAZINE." Nano 07, no. 06 (December 2012): 1250046. http://dx.doi.org/10.1142/s1793292012500464.

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II–VI Semiconductor nanocrystals (NCs) with tunable visible emission, such as CdS , CdSe and CdTe , were synthesized in aqueous solution using thiols as capping molecules. Hydrazine was found to promote the growth of NCs through a special mechanism. In only a few hours, the synthesis process was completed at room temperature. Under moderate conditions, the capping molecules not only changed the growth rate of NCs simply by varying the concentration, but also altered the spectral properties of NCs. The capping molecules with amino groups were propitious to the growth of CdS NCs, whereas the kinetic growth of CdS NCs was more affected by the surface passivation efficiency of NCs than by steric hindrance in the system. The fastest growth of the CdS NCs was achieved when glutathione was used as a capping molecule, while the emission of CdS and CdSe NCs were shown to remain steady and tunable using the same capping molecule. The growth rate of 3-mercaptopropionic acid-capped CdS and CdSe NCs slowed down significantly, while CdTe NCs were obtained with excellent emission properties when capped with the same molecule. Furthermore, our approach will also be useful for the study of the kinetic growth of NCs in aqueous solution.

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Galkin, Nikolay G., Konstantin Nickolaevich Galkin, Evgeniy Y. Subbotin, Evgeniy Anatoljevich Chusovotin, and Dmitrii L. Goroshko. "Multilayer Heterostructures with Embedded CrSi₂ and β-FeSi₂ Nanocrystals on Si(111) Substrate: From the Formation to Photoelectric Properties." Solid State Phenomena 312 (November 2020): 45–53. http://dx.doi.org/10.4028/www.scientific.net/ssp.312.45.

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The studies are devoted to the development of the technology of multilayer incorporation of nanocrystals (NCs) of semiconductor chromium and iron disilicides with a layer density no less than 2x1010 cm-2, the establishment of the growth mechanism of heterostructures with two types of NCs, the determination of their crystalline quality and optical properties, as well as the creation and study of rectification and photoelectric properties of p-i-n diodes based on them. Morphologically smooth heterostructures with 6 embedded layers of CrSi2 nanocrystals and two types of embedded nanocrystals (with 4 layers of CrSi2 NCs and 2 layers of β-FeSi2 NCs) for optical studies and built-in silicon p-i-n diodes were grown for the first time. The possibility of optical identification of interband transitions in embedded nanocrystals in the photon energy range of 1.2 - 2.5 eV was determined from the reflection spectra and the strongest peaks in reflection from the integrated nanocrystals were determined: 2.0 eV for CrSi2 NCs and 1.75 eV for β-FeSi2 NCs. The created p-i-n diodes have a contact potential difference of 0.95 V, regardless of the type of embedded NCs. At 80 K, an absorption band (0.7 - 1.1 eV) was detected in the diodes, which was associated with carrier photo generation in the embedded CrSi2 and β-FeSi2 NCs. From the spectra of the photoresponse at 80 K, the band gap widths in the NCs were determined: 0.50 eV in CrSi2 and 0.70 eV in the superposition of the CrSi2 and β-FeSi2 NCs.

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Tang, Rui Fan, Kai Huang, Guang Yang Lin, Huan Da Wu, Chen Li, and Hong Kai Lai. "Charge Trapping Properties of Au Nanocrystals with Various Sizes for Non-Volatile Memory Applications." Advanced Materials Research 787 (September 2013): 367–71. http://dx.doi.org/10.4028/www.scientific.net/amr.787.367.

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Charge trapping properties of Au nanocrystals (NCs) with various sizes and densities embedded in metal oxide semiconductor (MOS) were investigated. Comparing with the Nc size, experimental results show that the NC spacing is more influential in electron trapping. Au NCs with the size of 8~13nm have larger memory window than the Au NCs of 13-17nm and 6-8nm, which can be ascribe to the higher field-enhancement effect caused by the larger NC spacing. Optimized NC size can improve the specific characteristic of memory device effectively.

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Feng, Wen Ran, and Hai Zhou. "PbSe Nanocrystals Synthesized by an Ultrasonic Electrochemical Method." Advanced Materials Research 194-196 (February 2011): 545–48. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.545.

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Lead selenide (PbSe) is quite an important semiconductor material with several superior physical properties, e.g. optical and electrical ones. In this paper, PbSe nanocrystals (NCs) with different morphologies such as sphere, rod and hexagon were successfully prepared by an ultrasonic electrochemical method, using sodium citrate as the coordination agent, at room temperature. The crystal structure and the morphology of the as-prepared PbSe NCs were confirmed by means of the Transmission Electron Microscopy (TEM) and X-ray diffractometer (XRD). The ultraviolet-visible Spectrophotometer (UV) was performed to analyze the optical properties of the PbSe NCs. Results show that the nanospheres were about 60 nm in diameter, and the nanorods were 20 nm in diameter with a slenderness ratio of 25. The possible mechanism for the nanorods growth was discussed. The energy gap of the PbSe NCs deduced from the UV-visible spectra was much larger than their bulk counterparts, due to the quantum size effect.

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Yu, Hang, and Lei Tao. "A Novel Method for Preparing High Efficient Fluorescence-Encoded Microspheres with Semiconductor Nanocrystals." Advanced Materials Research 306-307 (August 2011): 1284–88. http://dx.doi.org/10.4028/www.scientific.net/amr.306-307.1284.

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A novel method with two steps for preparing high efficiency fluorescence nanocrystals (NCs)-encoded microspheres was developed. First, a series of polystyrene (PS) microspheres from 1 μm to 5 μm in diameter were prepared by dispersion polymerization; then, after a swelling process with CdSe NCs of different size the PS microspheres were encoded quantitatively. This method for fluorescence-encoding of microspheres was shown to have the following outstanding characteristics: (1) An emulsion containing CdSe NCs and swelling agents (chloroform) are firstly used for introduction of NCs into microspheres. (2) The embedded nanocrystals remain their original properties and they are not simply absorbed onto the surface of the microspheres but being carried into the inner of microspheres and so the NCs cannot be released or leaked out easily. As-prepared fluorescence-encoded microspheres could conjugate with proteins by some further surface modification, so they have a great potential to be applied to such fields as biochemistry, molecular biology, cell biology, immunology, etc. In addition, the method could be operated easily and reproducibly.

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Hou, Mingyue, Zhaohua Zhou, Ao Xu, Kening Xiao, Jiakun Li, Donghuan Qin, Wei Xu, and Lintao Hou. "Synthesis of Group II-VI Semiconductor Nanocrystals via Phosphine Free Method and Their Application in Solution Processed Photovoltaic Devices." Nanomaterials 11, no. 8 (August 15, 2021): 2071. http://dx.doi.org/10.3390/nano11082071.

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Solution-processed CdTe semiconductor nanocrystals (NCs) have exhibited astonishing potential in fabricating low-cost, low materials consumption and highly efficient photovoltaic devices. However, most of the conventional CdTe NCs reported are synthesized through high temperature microemulsion method with high toxic trioctylphosphine tellurite (TOP-Te) or tributylphosphine tellurite (TBP-Te) as tellurium precursor. These hazardous substances used in the fabrication process of CdTe NCs are drawing them back from further application. Herein, we report a phosphine-free method for synthesizing group II-VI semiconductor NCs with alkyl amine and alkyl acid as ligands. Based on various characterizations like UV-vis absorption (UV), transmission electron microscope (TEM), and X-ray diffraction (XRD), among others, the properties of the as-synthesized CdS, CdSe, and CdTe NCs are determined. High-quality semiconductor NCs with easily controlled size and morphology could be fabricated through this phosphine-free method. To further investigate its potential to industrial application, NCs solar cells with device configuration of ITO/ZnO/CdSe/CdTe/Au and ITO/ZnO/CdS/CdTe/Au are fabricated based on NCs synthesized by this method. By optimizing the device fabrication conditions, the champion device exhibited power conversion efficiency (PCE) of 2.28%. This research paves the way for industrial production of low-cost and environmentally friendly NCs photovoltaic devices.

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Schneider, R., F. Weigert, V. Lesnyak, S. Leubner, T. Lorenz, T. Behnke, A. Dubavik, et al. "pH and concentration dependence of the optical properties of thiol-capped CdTe nanocrystals in water and D2O." Physical Chemistry Chemical Physics 18, no. 28 (2016): 19083–92. http://dx.doi.org/10.1039/c6cp03123d.

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The optical properties of semiconductor nanocrystals (SC NCs) are largely controlled by their size and surface chemistry, i.e., the chemical nature and number of surface ligands as well as the strength of the particle-ligand bond.

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Pi, Xiaodong. "Doping Silicon Nanocrystals with Boron and Phosphorus." Journal of Nanomaterials 2012 (2012): 1–9. http://dx.doi.org/10.1155/2012/912903.

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The properties of silicon nanocrystals (Si NCs) that are usually a few nanometers in size can be exquisitely tuned by boron (B) and phosphorus (P) doping. Recent progress in the simulation of B- and P-doped Si NCs has led to improved explanation for B- and P-doping-induced changes in the optical properties of Si NCs. This is mainly enabled by comprehensive investigation on the locations of B and P in Si NCs and the electronic properties of B- and P-doped Si NCs. I remarks on the implications of newly gained insights on B- and P-doped Si NCs. Continuous research to advance the understanding of the doping of Si NCs with B and P is envisioned.

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SHEN, M. Y., M. ODA, T. GOTO, and T. YAO. "DYNAMICAL PROCESS OF PHOTOIONIZATION IN SEMICONDUCTOR NANOCRYSTALS." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3574–78. http://dx.doi.org/10.1142/s0217979201008184.

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When quantum dots (QDs) or nanocrystals (NCs) are photoionized, great changes of electric fields exerted on QDs occur, then photodarkening, photobrightening, and persistent hole burning effects may be macroscopically observed in QD system, and luminescence spectral diffusion and on/off behavior may be microscopically observed in a single QD. The dynamics of the emitted carrier from the QD by photoionization governs the properties of these phenomena. The photoionization process has been directly found in CdTe nanocrystals embedded in TOPO by measuring the temperature dependence of their photocurrent and photoluminescence. The phase transition of the matrix TOPO from amorphous solid to liquid makes the diffusion length of the emitted carriers outside the nanocrystals increase abruptly, resulting in a steep rise in both the photocurrent and the photoluminescence. Photoionization of a QD is fundamentally important to its optical properties

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Dzhagan, Volodymyr, Oleksandr Stroyuk, Oleksandra Raievska, Oksana Isaieva, Olga Kapush, Oleksandr Selyshchev, Volodymyr Yukhymchuk, Mykhailo Valakh, and Dietrich R. T. Zahn. "Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices." Nanomaterials 10, no. 12 (December 21, 2020): 2565. http://dx.doi.org/10.3390/nano10122565.

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The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental factors. Luminescent NCs in optically transparent polymers have been investigated due to their perspective applications in photonics and bio-imaging. Here, we report on the manifestations of photo-induced enhancement of photoluminescence (PL) of aqueous colloidal NCs embedded in water-soluble polymers. Based on the comparison of results obtained on bare and core/shell NCs, NCs of different compounds (CdSe, CdTe, ZnO) as well as different embedding polymers, we conclude on the most probable mechanism of the photoenhancement for these sorts of systems. Contrary to photoenhancement observed earlier as a result of surface photocorrosion, we do not observe any change in peak position and width of the excitonic PL. Therefore, we suggest that the saturation of trap states by accumulated photo-excited charges plays a key role in the observed enhancement of the radiative recombination. This suggestion is supported by the unique temperature dependence of the trap PL band as well as by power-dependent PL measurement.

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Milekhin, Ilya A., Alexander G. Milekhin, and Dietrich R. T. Zahn. "Surface- and Tip-Enhanced Raman Scattering by CdSe Nanocrystals on Plasmonic Substrates." Nanomaterials 12, no. 13 (June 26, 2022): 2197. http://dx.doi.org/10.3390/nano12132197.

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This work presents an overview of the latest results and new data on the optical response from spherical CdSe nanocrystals (NCs) obtained using surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS). SERS is based on the enhancement of the phonon response from nanoobjects such as molecules or inorganic nanostructures placed on metal nanostructured substrates with a localized surface plasmon resonance (LSPR). A drastic SERS enhancement for optical phonons in semiconductor nanostructures can be achieved by a proper choice of the plasmonic substrate, for which the LSPR energy coincides with the laser excitation energy. The resonant enhancement of the optical response makes it possible to detect mono- and submonolayer coatings of CdSe NCs. The combination of Raman scattering with atomic force microscopy (AFM) using a metallized probe represents the basis of TERS from semiconductor nanostructures and makes it possible to investigate their phonon properties with nanoscale spatial resolution. Gap-mode TERS provides further enhancement of Raman scattering by optical phonon modes of CdSe NCs with nanometer spatial resolution due to the highly localized electric field in the gap between the metal AFM tip and a plasmonic substrate and opens new pathways for the optical characterization of single semiconductor nanostructures and for revealing details of their phonon spectrum at the nanometer scale.

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Erdem, Talha, and Hilmi Volkan Demir. "Color-Enrichment Semiconductor Nanocrystals for Biorhythm-Friendly Backlighting." Zeitschrift für Physikalische Chemie 232, no. 9-11 (August 28, 2018): 1457–68. http://dx.doi.org/10.1515/zpch-2018-1134.

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Abstract 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.

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Lübkemann, Franziska, Timo C. Gusenburger, Dominik Hinrichs, Rasmus Himstedt, Dirk Dorfs, and Nadja C. Bigall. "Synthesis of InP/ZnS Nanocrystals and Phase Transfer by Hydrolysis of Ester." Zeitschrift für Physikalische Chemie 233, no. 1 (December 19, 2018): 55–67. http://dx.doi.org/10.1515/zpch-2018-1167.

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Abstract The synthesis of highly luminescent non-toxic nanocrystals (NCs) and the subsequent phase transfer to aqueous solution by hydrolysis of the crystal-bound ester are presented. Therefore, the synthesis of the spherical semiconductor system InP/ZnS was modified by changing the sulfur precursor in the synthesis from 1-dodecanethiol to dodecyl 3-mercaptopropionate (D3MP). By employing D3MP both as sulfur precursor for the ZnS shell growth and as stabilizing ligand, the phase transfer from organic to aqueous solution can be performed easily. Instead of the usually employed ligand exchange with mercaptopropionic acid, the NCs are only shaken with a sodium borate buffer in order to obtain aqueous soluble NCs by hydrolysis of the ester. In future work, the NCs must be protected against aggregation and the long term stability has to be increased. The optical properties of the samples are investigated by UV/Vis and photoluminescence spectroscopy, and the morphology of the nanoparticles (NPs) before and after phase transfer is determined by transmission electron microscopy.

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Xu, Rong Hui, Jiu Ba Wen, and Feng Zhang Ren. "Synthesis of CdS/CdCO₃ Core/Shell Structural Nanocrystals Potentially Used for Solar Cell via Hydrothermal Route." Applied Mechanics and Materials 79 (July 2011): 7–12. http://dx.doi.org/10.4028/www.scientific.net/amm.79.7.

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Synthesis of CdS/CdCO3Core/Shell semiconductor nanocrystals potentially used for solar cell via hydrothermal route is presented. Water-soluble crystallites with wurtzite crystal structure (CdS), hexagonal structure (CdCO3) with strong photoluminescence are prepared. The synthesis is based on the separation of the nucleation and growth stages of core and shell by controlling some crucial factors such as temperature, pH, ratio and concentration of reactant mixture. Bare wurtzite structural CdS nanocrystallites were synthesized by using cadmium acetate and thiourea as precursors. Ostwald ripening process under high temperature leads to high sample quality. Photoluminescence of nanocrystals with Core/Shell Structure and bare nanocrystals was compared and analysed. Nanocrystals with Core/Shell Structure have stabler performance of photoluminescence than CdS bare nanocrystallites because of the shell. Transmission electron microscopy and X-ray powder diffraction indicate the presence of bulk structural properties in crystallites as small as 5nm in diameter. X-ray Photoelectron Spectroscopy was used to characterize core/shell structure of as-prepared NCs. Ultra-stability and super strong photoluminescence emission of as-prepared CdS/CdCO3Core/Shell semiconductor nanocrystallites indicates its potentially practical value in NCs solar cell.

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McVey, Benjamin F. P., Robert A. Swain, Delphine Lagarde, Wilfried-Solo Ojo, Kaltoum Bakkouche, Cécile Marcelot, Bénédicte Warot, et al. "Cd3P2/Zn3P2 Core-Shell Nanocrystals: Synthesis and Optical Properties." Nanomaterials 12, no. 19 (September 27, 2022): 3364. http://dx.doi.org/10.3390/nano12193364.

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II–V semiconductor nanocrystals such as Cd3P2 and Zn3P2 have enormous potential as materials in next-generation optoelectronic devices requiring active optical properties across the visible and infrared range. To date, this potential has been unfulfilled due to their inherent instability with respect to air and moisture. Core-shell system Cd3P2/Zn3P2 is synthesized and studied from structural (morphology, crystallinity, shell diameter), chemical (composition of core, shell, and ligand sphere), and optical perspectives (absorbance, emission-steady state and time resolved, quantum yield, and air stability). The improvements achieved by coating with Zn3P2 are likely due to its identical crystal structure to Cd3P2 (tetragonal), highlighting the key role crystallographic concerns play in creating cutting edge core-shell NCs.

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Zhang, Zhijie, Rui Zhou, Deben Li, Ying Jiang, Xuesheng Wang, Huiling Tang, and Jiayue Xu. "Recent Progress in Halide Perovskite Nanocrystals for Photocatalytic Hydrogen Evolution." Nanomaterials 13, no. 1 (December 25, 2022): 106. http://dx.doi.org/10.3390/nano13010106.

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Due to its environmental cleanliness and high energy density, hydrogen has been deemed as a promising alternative to traditional fossil fuels. Photocatalytic water-splitting using semiconductor materials is a good prospect for hydrogen production in terms of renewable solar energy utilization. In recent years, halide perovskite nanocrystals (NCs) are emerging as a new class of fascinating nanomaterial for light harvesting and photocatalytic applications. This is due to their appealing optoelectronic properties, such as optimal band gaps, high absorption coefficient, high carrier mobility, long carrier diffusion length, etc. In this review, recent progress in halide perovskite NCs for photocatalytic hydrogen evolution is summarized. Emphasis is given to the current strategies that enhance the photocatalytic hydrogen production performance of halide perovskite NCs. Some scientific challenges and perspectives for halide perovskite photocatalysts are also proposed and discussed. It is anticipated that this review will provide valuable references for the future development of halide perovskite-based photocatalysts used in highly efficient hydrogen evolution.

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Apretna, Thibault, Sylvain Massabeau, Charlie Gréboval, Nicolas Goubet, Jérôme Tignon, Sukhdeep Dhillon, Francesca Carosella, Robson Ferreira, Emmanuel Lhuillier, and Juliette Mangeney. "Few picosecond dynamics of intraband transitions in THz HgTe nanocrystals." Nanophotonics 10, no. 10 (July 21, 2021): 2753–63. http://dx.doi.org/10.1515/nanoph-2021-0249.

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Abstract Optoelectronic devices based on intraband or intersublevel transitions in semiconductors are important building blocks of the current THz technology. Large nanocrystals (NCs) of Mercury telluride (HgTe) are promising semiconductor candidates owing to their intraband absorption peak tunable from 60 THz to 4 THz. However, the physical nature of this THz absorption remains elusive as, in this spectral range, quantum confinement and Coulomb repulsion effects can coexist. Further, the carrier dynamics at low energy in HgTe NCs, which strongly impact the performances of THz optoelectronic devices, is still unexplored. Here, we demonstrate a broad THz absorption resonance centered at ≈4.5 THz and fully interpret its characteristics with a quantum model describing multiple intraband transitions of single carriers between quantized states. Our analysis reveals the absence of collective excitations in the THz optical response of these self-doped large NCs. Furthermore, using optical pump-THz probe experiments, we report on carrier dynamics at low energy as long as 6 ps in these self-doped THz HgTe NCs. We highlight evidence that Auger recombination is irrelevant in this system and attribute the main carrier recombination process to direct energy transfer from the electronic transition to the ligand vibrational modes and to nonradiative recombination assisted by surface traps. Our study opens interesting perspectives for the use of large HgTe NCs for the development of advanced THz optoelectronic devices such as emitters and detectors and for quantum engineering at THz frequencies.

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Noh, Miru, and Y. S. Lee. "Optical Characterization on Perovskite Zirconate Nanocrystals." Journal of Nanoscience and Nanotechnology 15, no. 10 (October 1, 2015): 8267–70. http://dx.doi.org/10.1166/jnn.2015.11283.

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We performed an optical study on the electronic properties of perovskite zirconate AZrO3 (A = Ca and Ba) nanocrystals (NCs), which depend strongly on the size of A ion as well as the postannealing process. The zirconate NCs were synthesized in the combustion method, which was found to be quite effective for synthesizing highly orthorhombic CaZrO3 NCs in the sense that their grain sizes are relatively larger and as-synthesized NCs do not include any raw material phase in the XRD pattern, compared with the cubic BaZrO3 NCs.The room-temperature visible emission is commonly quite strong in both NCs. Interestingly, the dominance of the green-yellow emission over the violet-blue emission with increasing the post-annealing temperature (Tanneal) appears to be in agreement with the formation of the mid-gap state identified in the absorption spectra. While the optical bandgaps of NCs increased with increasing Tanneal, a systematic trend that the optical bandgap in the AZrO3 NCs decreased with the increasingly larger size of the A ion occurred. We discuss our findings in relation to the oxygen vacancy formation, lattice distortion, and size effect.

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Kriegel, Ilka, and Francesco Scotognella. "Tunable light filtering by a Bragg mirror/heavily doped semiconducting nanocrystal composite." Beilstein Journal of Nanotechnology 6 (January 16, 2015): 193–200. http://dx.doi.org/10.3762/bjnano.6.18.

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Tunable light filters are critical components for many optical applications in which light in-coupling, out-coupling or rejection is crucial, such as lasing, sensing, photovoltaics and information and communication technology. For this purpose, Bragg mirrors (band-pass filters with high reflectivity) represent good candidates. However, their optical characteristics are determined during the fabrication stage. Heavily doped semiconductor nanocrystals (NCs), on the other hand, deliver a high degree of optical tunability through the active modulation of their carrier density, ultimately influencing their plasmonic absorption properties. Here, we propose the design of an actively tunable light filter composed of a Bragg mirror and a layer of plasmonic semiconductor NCs. We demonstrate that the filtering properties of the coupled device can be tuned to cover a wide range of frequencies from the visible to the near infrared (vis–NIR) spectral region when employing varying carrier densities. As the tunable component, we implemented a dispersion of copper selenide (Cu2−xSe) NCs and a film of indium tin oxide (ITO) NCs, which are known to show optical tunablility with chemical or electrochemical treatments. We utilized the Mie theory to describe the carrier-dependent plasmonic properties of the Cu2−x Se NC dispersion and the effective medium theory to describe the optical characteristics of the ITO film. The transmission properties of the Bragg mirror have been modelled with the transfer matrix method. We foresee ease of experimental realization of the coupled device, where filtering modulation is achieved upon chemical and electrochemical post-fabrication treatment of the heavily doped semiconductor NC component, eventually resulting in tunable transmission properties of the coupled device.

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Onishchuk, D. A., P. S. Parfenov, A. Dubavik, and A. P. Litvin. "The Influence of the Schottky Barrier at the Metal/PbS NCs Junction on the Charge Transport Properties-=SUP=-*-=/SUP=-." Журнал технической физики 128, no. 8 (2020): 1194. http://dx.doi.org/10.21883/os.2020.08.49725.1002-20.

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The effect of the Schottky barrier height changes on the metal/EDT-treated (1,2-ethanedithiol) PbS nanocrystals film interface is considered. Also, the influence of shunts on the J-V characteristic and the Schottky barrier height is demonstrated, as well, the effect of silver oxide layer on the charge accumulation and tunneling. It is shown that the gold electrodes provide more stable results even when the Schottky barrier is formed, while the silver electrode provides more current. Keywords: semiconductor nanocrystals, Schottky barrier, charge carriers transport, thin films.

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Hua, Yan, Yuming Wei, Bo Chen, Zhuojun Liu, Zhe He, Zeyu Xing, Shunfa Liu, et al. "Directional and Fast Photoluminescence from CsPbI3 Nanocrystals Coupled to Dielectric Circular Bragg Gratings." Micromachines 12, no. 4 (April 13, 2021): 422. http://dx.doi.org/10.3390/mi12040422.

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Lead halide perovskite nanocrystals (NCs), especially the all-inorganic perovskite NCs, have drawn substantial attention for both fundamental research and device applications in recent years due to their unique optoelectronic properties. To build high-performance nanophotonic devices based on perovskite NCs, it is highly desirable to couple the NCs to photonic nanostructures for enhancing the radiative emission rate and improving the emission directionality of the NCs. In this work, we synthesized high-quality CsPbI3 NCs and further coupled them to dielectric circular Bragg gratings (CBGs). The efficient couplings between the perovskite NCs and the CBGs resulted in a 45.9-fold enhancement of the photoluminescence (PL) intensity and 3.2-fold acceleration of the radiative emission rate. Our work serves as an important step for building high-performance nanophotonic light emitting devices by integrating perovskite NCs with photonic nanostructures.

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Li, Zongtao, Cunjiang Song, Longshi Rao, Hanguang Lu, Caiman Yan, Kai Cao, Xinrui Ding, Binhai Yu, and Yong Tang. "Synthesis of Highly Photoluminescent All-Inorganic CsPbX3 Nanocrystals via Interfacial Anion Exchange Reactions." Nanomaterials 9, no. 9 (September 11, 2019): 1296. http://dx.doi.org/10.3390/nano9091296.

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All-inorganic cesium lead halide perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) have attracted significant attention owing to their fascinating electronic and optical properties. However, researchers still face challenges to achieve highly stable and photoluminescent CsPbX3 NCs at room temperature by the direct-synthesis method. Herein, we synthesize CsPbX3 NCs by a facile and environmentally friendly method, which uses an aqueous solution of metal halides to react with Cs4PbBr6 NCs via interfacial anion exchange reactions and without applying any pretreatment. This method produces monodisperse and air-stable CsPbX3 NCs with tunable spectra covering the entire visible range, narrow photoluminescence emission bandwidth, and high photoluminescence quantum yield (PL QY, 80%). In addition, the chemical transformation mechanism between Cs4PbBr6 NCs and CsPbX3 NCs was investigated. The Cs4PbBr6 NCs were converted to CsPbBr3 NCs first by stripping CsBr, and then, the as-prepared CsPbBr3 NCs reacted with metal halides to form CsPbX3 NCs. This work takes advantage of the chemical transformation mechanism of Cs4PbBr6 NCs and provides an efficient and environmentally friendly way to synthesize CsPbX3 NCs.

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Domashevskaya, Evelina P., Sergey A. Ivkov, Pavel V. Seredin, Dmitry L. Goloshchapov, Konstantin A. Barkov, Stanislav V. Ryabtsev, Yrii G. Segal, Alexander V. Sitnikov, and Elena A. Ganshina. "Nonlinear Electromagnetic Properties of Thinfilm Nanocomposites (CoFeZr)x(MgF2)100−x." Magnetochemistry 9, no. 6 (June 20, 2023): 160. http://dx.doi.org/10.3390/magnetochemistry9060160.

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The aim of this work is a comprehensive study of the effect of variable atomic composition and structural-phase state of (CoFeZr)x(MgF2)100−x nanocomposites (NCs) on their nonlinear electronic and magnetic/magneto-optical properties. Micrometer-thick nanocomposite layers on the glass substrates were obtained by ion-beam sputtering of a composite target in the argon atmosphere in a wide range of compositions x = 9–51 at·%. The value of the resistive percolation threshold, xper = 34 at·%, determined from the concentration dependencies of the electrical resistance of NCs, coincides with the beginning of nucleation of metallic nanocrystals CoFeZr in MgF2 dielectric matrix. The absolute value of maximum magnetoresistance of NCs is 2.4% in a magnetic field of 5.5 kG at x = 25 at·%, up to the percolation threshold. Two maxima appear in the concentration dependencies of magneto-optical transversal Kerr effect, one of which, at x = 34 at·%, corresponds to the formation of CoFeZr alloy nanocrystals of a hexagonal structure, and the second one at x = 45 at·% corresponds to the phase transition of nanocrystals from a hexagonal to a cubic body-centered structure. The magnetic percolation threshold in (CoFeZr)x(MgF2)100−x system at xfm = 34 at·%, with the appearance of a hysteresis loop and a coercive force of Hc ≈ 8 Oe, coincides with the resistive percolation threshold xper = 34 at·%. Concentration dependence of the coercive force showed that at low contents of metallic alloy x < 30 at·%, NCs are superparamagnetic (Hc = 0). With an increase of the alloy content, in the region of magnetic and resistive percolation thresholds, NCs exhibit a magnetically soft ferromagnetic character and do not change it far beyond the percolation threshold, with the maximum value of the coercive force Hc < 30 Oe.

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Matsumura, Takashi, Atsushi Miura, Takio Hikono, and Yukiharu Uraoka. "Forming Fe nanocrystals by reduction of ferritin nanocores for metal nanocrystal memory." AIP Advances 12, no. 5 (May 1, 2022): 055029. http://dx.doi.org/10.1063/5.0092210.

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To fabricate metal nanocrystal (NC) memories based on iron ferritin proteins, we propose a method for embedding ferritin cores in SiO2 and performing a reduction process by rapid thermal annealing (RTA) in a hydrogen atmosphere. An iron oxide core biochemically synthesized by ferritin was used to fabricate a high-density memory node array of 7.7 × 1011 dots/cm2. Reduction intermediates and metallic iron NCs were obtained in a short time by using a hydrogen atmosphere RTA with the iron oxide core embedded in SiO2. Metal-oxide-semiconductor memory structures were fabricated, capacitance–voltage (C–V) measurements were performed, and hysteresis (memory window) suggesting charging and discharging of NCs was observed. Furthermore, the memory window and the charge injection threshold tended to vary depending on the reduction temperature. Since these values are proportional to the magnitude of the dot work function (or electron affinity), it is assumed that the formation of reduced intermediates NCs with varying work functions depending on the treatment temperature affects the electrical properties. The results suggest that the work function of the charge retention node can be controlled by reducing the metal oxide, enabling a new approach to memory design that actively employs the reduction process.

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Wang, Jintao, Chuanxiang Ye, Xiaowei Wu, and Zhijian Zheng. "Optical Properties of Cu-Doped Perovskite Nanoplatelets." Journal of Nanoelectronics and Optoelectronics 18, no. 1 (January 1, 2023): 1–5. http://dx.doi.org/10.1166/jno.2023.3359.

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All inorganic perovskite nanocrystals (NCs) have been widely concerned for their unique optical properties. However, due to the rotation and inclining of the [PbX6]4− octahedron caused by Cs ions, such kind of materials usually have poor stability, which will hinder their commercialization. It is well known that using smaller divalent cations to replace Pb2+ can effectively improve the stability and luminescence properties of CsPbX3 NCs. In this work, Cu-doped CsPbBr3 nanoplatelets (NPs) are prepared, i.e., CsPb0.95Cu0.05Br3 NPs, and their temperature dependent emission properties have been investigated. The experimental results show that Cu-doping method can weaken the thermal expansion effect and electron-phonon interaction strength of perovskite NPs. Although the exciton binding energy of CsPb0.95Cu0.05Br3 NPs is smaller than that of CsPbBr3 NPs, it is still much larger than that of CsPbBr3 cubic NCs. Our experimental results will be of significance for the development of optoelectronic devices based on transition metal doped perovskite NPs.

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Zhou, Jigang, Xingtai Zhou, Xuhui Sun, Michael Murphy, Franziskus Heigl, Tsun-Kong Sham, and Zhifeng Ding. "Electronic structures of CdSe nanocrystals — An X-ray absorption near-edge structure (XANES) investigation." Canadian Journal of Chemistry 85, no. 10 (October 1, 2007): 756–60. http://dx.doi.org/10.1139/v07-080.

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CdSe nanocrystals (NCs), capped with trioctylphosphine oxide and 1-octadecanamine, have been synthesized with colloidal methods. Both UV–vis absorption and photoluminescence spectra show that the prepared nanostructures exhibit a quantum confinement effect. X-ray absorption near–edge structure (XANES) at Se K-edge recorded in fluorescence yield mode have been carried out on these NCs, with different size and capping ligands to gain insight into how their electronic structures are affected by the NC size and chemical properties of the ligands. The results indicate that XANES are sensitive to both the NC size and the nature of the capping ligands. The whiteline intensity in XANES spectra can be related to the photoluminescence properties of these NCs.Key words: CdSe nanocrystals, capping ligands, X-ray absorption near-edge structure, UV–vis spectroscopy, photoluminescence.

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Nomoto, Keita, Xiang-Yuan Cui, Andrew Breen, Anna V. Ceguerra, Ivan Perez-Wurfl, Gavin Conibeer, and Simon P. Ringer. "Effects of thermal annealing on the distribution of boron and phosphorus in p-i-n structured silicon nanocrystals embedded in silicon dioxide." Nanotechnology 33, no. 7 (November 26, 2021): 075709. http://dx.doi.org/10.1088/1361-6528/ac38e6.

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Abstract Thermal annealing temperature and time dictate the microstructure of semiconductor materials such as silicon nanocrystals (Si NCs). Herein, atom probe tomography (APT) and density functional theory (DFT) calculations are used to understand the thermal annealing temperature effects on Si NCs grown in a SiO2 matrix and the distribution behaviour of boron (B) and phosphorus (P) dopant atoms. The APT results demonstrate that raising the annealing temperature promotes growth and increased P concentration of the Si NCs. The data also shows that the thermal annealing does not promote the incorporation of B atoms into Si NCs. Instead, B atoms tend to locate at the interface between the Si NCs and SiO2 matrix. The DFT calculations support the APT data and reveal that oxygen vacancies regulate Si NC growth and dopant distribution. This study provides the detailed microstructure of p-type, intrinsic, and n-type Si NCs with changing annealing temperature and highlights how B and P dopants preferentially locate with respect to the Si NCs embedded in the SiO2 matrix with the aid of oxygen vacancies. These findings will be useful towards future optoelectronic applications.

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Lippens, P. E., and M. Lannoo. "Optical properties of II-VI semiconductor nanocrystals." Semiconductor Science and Technology 6, no. 9A (September 1, 1991): A157—A160. http://dx.doi.org/10.1088/0268-1242/6/9a/030.

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Na, Guangren, Yawen li, Xiaoyu Wang, Yuhao Fu, and Lijun Zhang. "Electronic and optical properties of tapered tetrahedral semiconductor nanocrystals." Nanotechnology 32, no. 29 (April 30, 2021): 295203. http://dx.doi.org/10.1088/1361-6528/abf68f.

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Qu, Fanyao, A. M. Alcalde, C. G. Almeida, and Noelio Oliveira Dantas. "Finite element method for electronic properties of semiconductor nanocrystals." Journal of Applied Physics 94, no. 5 (September 2003): 3462–69. http://dx.doi.org/10.1063/1.1593221.

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Luo, Wenqin, Yongsheng Liu, and Xueyuan Chen. "Lanthanide-doped semiconductor nanocrystals: electronic structures and optical properties." Science China Materials 58, no. 10 (October 2015): 819–50. http://dx.doi.org/10.1007/s40843-015-0091-9.

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Eljarrat, Alberto, Lluís López-Conesa, Julian López-Vidrier, Sergi Hernández, Blas Garrido, César Magén, Francesca Peiró, and Sònia Estradé. "Retrieving the electronic properties of silicon nanocrystals embedded in a dielectric matrix by low-loss EELS." Nanoscale 6, no. 24 (2014): 14971–83. http://dx.doi.org/10.1039/c4nr03691c.

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Song, Jing, Xiaoxia Xu, Jihuai Wu, and Zhang Lan. "Low-temperature solution-processing high quality Nb-doped SnO2 nanocrystals-based electron transport layers for efficient planar perovskite solar cells." Functional Materials Letters 12, no. 01 (January 21, 2019): 1850091. http://dx.doi.org/10.1142/s1793604718500911.

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Low-temperature solution-processing method is a kind of low-energy-consuming and simple methodology for preparing cost-effective planar perovskite solar cells (PSCs). To achieve high-effciency planar PSCs, the quality of electron-transporting layers (ETLs) play a key role. The solvothermal-synthesized organic ligands capped semiconductor nanocrystals (NCs) not only have high crystallinity but also show excellent film-formation. Nevertheless, the biggest problem is that these organic ligands will form insulating barriers around the NCs, which will seriously hinder electronic coupling and limit performance of the corresponding devices. Therefore, the stripping treatment for organic ligands, which is not only complex but also has destructive influence on the quality of films, is traditionally used for achieving good performance. Here, we select high crystalline oleic acid-capped SnO2 NCs to prepare ETLs with low-temperature solution-processed methodology without complex ligand stripping step. We use Nb[Formula: see text] doping route to further enhance photovoltaic performance of the planar PSCs. The champion PSC based on Nb-doped SnO2 NCs ETL achieves a power conversion efficiency of 20.07%.

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Lee, Bryan, Tristan Hegseth, and Xiaoshan Zhu. "Optical Properties of Mn-Doped CuGa(In)S-ZnS Nanocrystals (NCs): Effects of Host NC and Mn Concentration." Nanomaterials 12, no. 6 (March 17, 2022): 994. http://dx.doi.org/10.3390/nano12060994.

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Time-gated fluorescence measurement (TGFM) using long-life fluorescence probes is a highly sensitive fluorescence-measurement technology due to the inherently high signal-to-background ratio. Although many probes for TGFM such as luminescent-metal-complex probes and lanthanide-doped nanoparticles are in development, they generally need sophisticated/expensive instruments for biosensing/imaging applications. Probes possessing high brightness, low-energy (visible light) excitation, and long lifetimes up to milliseconds of luminescence, are highly desired in order to simplify the optical and electronic design of time-gated instruments (e.g., adopting non-UV-grade optics or low-speed electronics), lower the instrument complexity and cost, and facilitate broader applications of TGFM. In this work, we developed Mn-doped CuGa(In)S-ZnS nanocrystals (NCs) using simple and standard synthetic steps to achieve all the desired optical features in order to investigate how the optical properties (fluorescence/absorption spectra, brightness, and lifetimes) of the Mn-doped NCs are affected by different host NCs and Mn concentrations in host NCs. With optimal synthetic conditions, a library of Mn-doped NCs was achieved that possessed high brightness (up to 47% quantum yield), low-energy excitation (by 405 nm visible light), and long lifetimes (up to 3.67 ms). Additionally, the time-domain fluorescence characteristics of optimal Mn-doped NCs were measured under pulsed 405 nm laser excitation and bandpass-filter-based emission collection. The measurement results indicate the feasibility of these optimal Mn-doped NCs in TGFM-based biosensing/imaging.

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49

Yun, Hongseok, and Taejong Paik. "Colloidal Self-Assembly of Inorganic Nanocrystals into Superlattice Thin-Films and Multiscale Nanostructures." Nanomaterials 9, no. 9 (September 1, 2019): 1243. http://dx.doi.org/10.3390/nano9091243.

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The self-assembly of colloidal inorganic nanocrystals (NCs) offers tremendous potential for the design of solution-processed multi-functional inorganic thin-films or nanostructures. To date, the self-assembly of various inorganic NCs, such as plasmonic metal, metal oxide, quantum dots, magnetics, and dielectrics, are reported to form single, binary, and even ternary superlattices with long-range orientational and positional order over a large area. In addition, the controlled coupling between NC building blocks in the highly ordered superlattices gives rise to novel collective properties, providing unique optical, magnetic, electronic, and catalytic properties. In this review, we introduce the self-assembly of inorganic NCs and the experimental process to form single and multicomponent superlattices, and we also describe the fabrication of multiscale NC superlattices with anisotropic NC building blocks, thin-film patterning, and the supracrystal formation of superlattice structures.

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50

Dzhagan, Volodymyr, Nazar Mazur, Olga Kapush, Oleksandr Selyshchev, Anatolii Karnaukhov, Oleg A. Yeshchenko, Mykola I. Danylenko, Volodymyr Yukhymchuk, and Dietrich R. T. Zahn. "Core and Shell Contributions to the Phonon Spectra of CdTe/CdS Quantum Dots." Nanomaterials 13, no. 5 (March 1, 2023): 921. http://dx.doi.org/10.3390/nano13050921.

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The parameters of the shell and interface in semiconductor core/shell nanocrystals (NCs) are determinant for their optical properties and charge transfer but are challenging to be studied. Raman spectroscopy was shown earlier to be a suitable informative probe of the core/shell structure. Here, we report the results of a spectroscopic study of CdTe NCs synthesized by a facile route in water, using thioglycolic acid (TGA) as a stabilizer. Both core-level X-ray photoelectron (XPS) and vibrational (Raman and infrared) spectra show that using thiol during the synthesis results in the formation of a CdS shell around the CdTe core NCs. Even though the spectral positions of the optical absorption and photoluminescence bands of such NCs are determined by the CdTe core, the far-infrared absorption and resonant Raman scattering spectra are dominated by the vibrations related with the shell. The physical mechanism of the observed effect is discussed and opposed to the results reported before for thiol-free CdTe Ns as well as CdSe/CdS and CdSe/ZnS core/shell NC systems, where the core phonons were clearly detected under similar experimental conditions.

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Journal articles on the topic 'Electronic Properties - Semiconductor Nanocrystals (NCs)'

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