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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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Lin, Chien-Chung, Hao-Chung Kuo, Guan-Ying Lee, Han-Yu Chao, and Shao-Yi Weng. "77‐1: Invited Paper: The Colloidal Quantum Dot Based Color Conversion Layer for Micro LED Arrays." SID Symposium Digest of Technical Papers 54, no. 1 (June 2023): 1087–90. http://dx.doi.org/10.1002/sdtp.16760.
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The advances of micro LEDs and colloidal quantum dots have provided a great platform for the next generation of micro displays. Although the illuminating efficiency of colloidal quantum dots is close to 100%, the patterning of these nanocrystals is still important and need to be developed. We use semiconductor grade fabrication to obtain small pixels smaller than 10 micrometers and a large scale formation of array. The photonic characterization reveals the conversion efficiency is 20% and the excitation wavelength dependent behavior is also probed. A 1300‐hour of vacuum storage test showed this type of color conversion layer is stable and the emission wavelength and linewidth are almost unchanged.
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Cortés-Villena, Alejandro, and Raquel E. Galian. "Present and Perspectives of Photoactive Porous Composites Based on Semiconductor Nanocrystals and Metal-Organic Frameworks." Molecules 26, no. 18 (September 16, 2021): 5620. http://dx.doi.org/10.3390/molecules26185620.
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This review focuses on the recent developments in synthesis, properties, and applications of a relatively new family of photoactive porous composites, integrated by metal halide perovskite (MHP) nanocrystals and metal-organic frameworks (MOFs). The synergy between the two systems has led to materials (MHP@MOF composites) with new functionalities along with improved properties and phase stability, thus broadening their applications in multiple areas of research such as sensing, light-harvesting solar cells, light-emitting device technology, encryption, and photocatalysis. The state of the art, recent progress, and most promising routes for future research on these photoactive porous composites are presented in the end.
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Keshari, Ashish K., and Avinash C. Pandey. "Size and Distribution: A Comparison of XRD, SAXS and SANS Study of II–VI Semiconductor Nanocrystals." Journal of Nanoscience and Nanotechnology 8, no. 3 (March 1, 2008): 1221–27. http://dx.doi.org/10.1166/jnn.2008.370.
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The uniqueness of size dependent functional properties of II–VI semiconductor nanocrystals have led to the development of various techniques for determination of shape, size and distributions, although the accurate measurements of the particle sizes has always been a fundamental task in nanoscience and even become more crucial with the discovery of quantum confinement effect. Acomparison of the well established techniques X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) with an emphasis on size and distribution of the prepared samples are reported in order to elaborate more precise techniques for the analysis of particles sizes. Modified Scherrer formula for spherical particles has been used to calculate the particle sizes from XRD spectra. Analysis of SAXS data has been reported using Guinier model. Small angle neutron scattering measurements has been performed for ZnO nanocrystals and the scattering data obtained is simulated for polydisperse sphere. The bare ZnO, ZnS and CdS and doped with Mn2+ systems are taken within the framework of our discussion. These materials were synthesized by chemical precipitation route and found to have size distribution from 2 to 6 nm for spherical particles. Sizes determined from various techniques are in good agreement with each other however small angle scattering technique is more reliable than XRD to determine the sizes of the nanoparticles.
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Lin, Weyde M. M., Maksym Yarema, Mengxia Liu, Edward Sargent, and Vanessa Wood. "Nanocrystal Quantum Dot Devices: How the Lead Sulfide (PbS) System Teaches Us the Importance of Surfaces." CHIMIA International Journal for Chemistry 75, no. 5 (May 28, 2021): 398–413. http://dx.doi.org/10.2533/chimia.2021.398.
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Semiconducting thin films made from nanocrystals hold potential as composite hybrid materials with new functionalities. With nanocrystal syntheses, composition can be controlled at the sub-nanometer level, and, by tuning size, shape, and surface termination of the nanocrystals as well as their packing, it is possible to select the electronic, phononic, and photonic properties of the resulting thin films. While the ability to tune the properties of a semiconductor from the atomistic- to macro-scale using solution-based techniques presents unique opportunities, it also introduces challenges for process control and reproducibility. In this review, we use the example of well-studied lead sulfide (PbS) nanocrystals and describe the key advances in nanocrystal synthesis and thin-film fabrication that have enabled improvement in performance of photovoltaic devices. While research moves forward with novel nanocrystal materials, it is important to consider what decades of work on PbS nanocrystals has taught us and how we can apply these learnings to realize the full potential of nanocrystal solids as highly flexible materials systems for functional semiconductor thin-film devices. One key lesson is the importance of controlling and manipulating surfaces.
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Kulakci, M., U. Serincan, and R. Turan. "Electroluminescence generated by a metal oxide semiconductor light emitting diode (MOS-LED) with Si nanocrystals embedded in SiO2layers by ion implantation." Semiconductor Science and Technology 21, no. 12 (September 25, 2006): 1527–32. http://dx.doi.org/10.1088/0268-1242/21/12/004.
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Astankova, K. N., A. S. Kozhukhov, G. K. Krivyakin, Y. A. Zhivodkov, D. V. Sheglov, and V. A. Volodin. "Interaction of low-fluence femtosecond laser pulses with a composite layer containing Ge nanoclusters: A novel type of nanofoam formation." Journal of Laser Applications 34, no. 2 (May 2022): 022002. http://dx.doi.org/10.2351/7.0000620.
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In the present work, the low-fluence nonablating femtosecond laser irradiation (λ = 800 nm) of the GeO2 layer with Ge nanoclusters protected by SiO2 layers is studied by different types of microscopy (optical microscopy, atomic force microscopy, and scanning and transmittance electron microscopy) and Raman spectroscopy. After the laser modification, the multilayer thickness increased by 6%–29% depending on the laser fluence. It was found that the laser fluence of ∼40 mJ/cm2 was the optimal value for observing the swelling effect and was below the ablation threshold. Irradiation at this fluence led the Ge nanoclusters to decrease in size from 5–8 to ∼2 nm and crystallize, while the GeO2 matrix expanded due to the formation of GeO bubbles. The fabrication mechanism of the novel type of nanofoam consisting of a glassy matrix, cavities filled with gas, and semiconductor nanocrystals with reduced size dispersion is discussed. Presumably, this effect is associated with the selective absorption of IR (800 nm) laser radiation by Ge nanoclusters.
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Wang, Shiwei, Weiqiang Bo, Min Zhong, Cong Liu, Ying Li, Mingyuan Zhu, Yemin Hu, and Hongmin Jin. "Effect of Cr Content on the Properties of Magnetic Field Processed Cr-Doped ZnO-Diluted Magnetic Semiconductors." Journal of Nanomaterials 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/501069.
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Cr-doped ZnO-diluted magnetic semiconductor (DMS) nanocrystals with various Cr contents were synthesized by hydrothermal method under high magnetic field. The result indicated that both the amount of Cr contents and high magnetic field significantly influenced crystal structure, morphology, and magnetic property of Cr-doped ZnO DMSs. When the Cr contents increased from 1 at% to 5 at%, the morphology of grains sequentially changed from flower-like to rod-like and then to the flake-like form. All the samples remained hexagonal wurtzite structure after Cr ions were doped into the ZnO crystal lattice. The Cr doping led to the increasing amount of defects and even enhanced the magnetic property of the matrix materials. All the Cr-doped ZnO DMSs obtained under high magnetic field exhibited obvious ferromagnetic behavior at room temperature. The results have also shown the successful substitution of the Cr3+ions for the Zn2+ions in the crystal lattice.
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Erdem, Talha, and Hilmi Volkan Demir. "Color science of nanocrystal quantum dots for lighting and displays." Nanophotonics 2, no. 1 (February 1, 2013): 57–81. http://dx.doi.org/10.1515/nanoph-2012-0031.
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AbstractColloidal nanocrystals of semiconductor quantum dots (QDs) are gaining prominence among the optoelectronic materials in the photonics industry. Among their many applications, their use in artificial lighting and displays has attracted special attention thanks to their high efficiency and narrow emission band, enabling spectral purity and fine tunability. By employing QDs in color-conversion LEDs, it is possible to simultaneously accomplish successful color rendition of the illuminated objects together with a good spectral overlap between the emission spectrum of the device and the sensitivity of the human eye, in addition to a warm white color, in contrast to other conventional sources such as incandescent and fluorescent lamps, and phosphor-based LEDs, which cannot achieve all of these properties at the same time. In this review, we summarize the color science of QDs for lighting and displays, and present the recent developments in QD-integrated LEDs and display research. First, we start with a general introduction to color science, photometry, and radiometry. After presenting an overview of QDs, we continue with the spectral designs of QD-integrated white LEDs that have led to efficient lighting for indoor and outdoor applications. Subsequently, we discuss QD color-conversion LEDs and displays as proof-of-concept applications – a new paradigm in artificial lighting and displays. Finally, we conclude with a summary of research opportunities and challenges along with a future outlook.
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Coropceanu, Igor, Eric M. Janke, Joshua Portner, Danny Haubold, Trung Dac Nguyen, Avishek Das, Christian P. N. Tanner, et al. "Self-assembly of nanocrystals into strongly electronically coupled all-inorganic supercrystals." Science 375, no. 6587 (March 25, 2022): 1422–26. http://dx.doi.org/10.1126/science.abm6753.
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Colloidal nanocrystals of metals, semiconductors, and other functional materials can self-assemble into long-range ordered crystalline and quasicrystalline phases, but insulating organic surface ligands prevent the development of collective electronic states in ordered nanocrystal assemblies. We reversibly self-assembled colloidal nanocrystals of gold, platinum, nickel, lead sulfide, and lead selenide with conductive inorganic ligands into supercrystals exhibiting optical and electronic properties consistent with strong electronic coupling between the constituent nanocrystals. The phase behavior of charge-stabilized nanocrystals can be rationalized and navigated with phase diagrams computed for particles interacting through short-range attractive potentials. By finely tuning interparticle interactions, the assembly was directed either through one-step nucleation or nonclassical two-step nucleation pathways. In the latter case, the nucleation was preceded by the formation of two metastable colloidal fluids.
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Thung, Yi Tian, Zitong Zhang, Fei Yan, Hilmi Volkan Demir, and Handong Sun. "Narrow electroluminescence in bromide ligand-capped cadmium chalcogenide nanoplatelets." Applied Physics Letters 120, no. 24 (June 13, 2022): 241105. http://dx.doi.org/10.1063/5.0094798.
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Colloidal zinc blende II–VI semiconductor nanoplatelets (NPLs) demonstrate as a promising class of materials for optoelectronic devices due to their unique excitonic characteristics, narrow emission linewidth, and quantum well-structure. Adopting heterostructures for these nanocrystals allows tuning of their optical features and enhances their photostability, photoluminescence (PL), quantum yield (QY), and color purity for further device integration. Exchanging of carboxylate capping ligands on top and bottom [001] facets of CdSe NPLs with halide ligands is an alternative to achieve the aims of spectral tunability and improve surface passivation, but to date there have been no reports on integrating the advantages of halide ligand exchanged CdSe NPLs for device fabrication. In this work, we demonstrate green electroluminescence (EL) of bromide ligand-capped CdSe NPLs as active emitters in an electrically driven light emitting diode (LED) with a low turn-on voltage of 3.0 V. We observed EL emission at 533.1 nm with a narrow linewidth of 19.4 nm, a maximum luminance of 1276 cd/m2, and the highest external quantum efficiency (EQE) of 0.803%. These results highlight the ability of halide ligand exchange in tuning the EL properties of CdSe NPL-LEDs and potential of bromide ligand-capped CdSe NPLs in contributing to the green emission region of NPL-LEDs, demonstrating its potential for future device integration and contribution to a high color rendering index of future NPL displays.
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Zhou, W. L., J. Wiemann, K. L. Stokes, and C. J. O’Connor. "Monodisperse Pbse Nanoparticle Self-Assembling Nanoarrays Before and After Annealing." Microscopy and Microanalysis 7, S2 (August 2001): 314–15. http://dx.doi.org/10.1017/s1431927600027641.
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A variety of semiconductor and metal nanoparticles can be synthesized and tunable in size from about 10 to 200 Å using size-selective separation technique. Preparation of monodisperse samples enables systematic characterization of the structural, electron, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close-packed, glassy and ordered nanocrystal. At inter-particle separations 5-100 Å, dipole-dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. The fabrication of monodisperse ordered nanoarrays with the inter-particle separations less than 5Å will be very important to study its physical properties since interaction between neighboring nanocrystals cause otherwise insulating assemblies to become semiconducting, metallic, or superconducting depending on nanocrystals composition. Here we present the fabrication of monodisperse PbSe nanoarrays with inter-particle distance less than 5 Å and its nanostructure study.
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Pascazio, Roberta, Juliette Zito, and Ivan Infante. "An Overview of Computational Studies on Colloidal Semiconductor Nanocrystals." CHIMIA International Journal for Chemistry 75, no. 5 (May 28, 2021): 427–34. http://dx.doi.org/10.2533/chimia.2021.427.
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In the last two decades, colloidal semiconductor nanocrystals have emerged as a phenomenal research topic due to their size-dependent optoelectronic properties and to their outstanding versatility in many technological applications. In this review, we provide an historical account of the most relevant computational works that have been carried out to understand atomistically the electronic structure of these materials, including the main requirements needed for the preparation of nanocrystal models that align well with the experiments. We further discuss how the advancement of these computational tools has affected the analysis of these nanomaterials over the years. We focus our review on the three main families of colloidal semiconductor nanocrystals: group II-VI and IV-VI metal chalcogenides, group III-V metal pnictogenides and metal halides, in particular lead-based halide perovskites. We discuss the most recent research frontiers and outline the future outlooks expected in this field from a computational perspective.
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Meng, Lingju, and Xihua Wang. "Doping Colloidal Quantum Dot Materials and Devices for Photovoltaics." Energies 15, no. 7 (March 27, 2022): 2458. http://dx.doi.org/10.3390/en15072458.
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Colloidal semiconductor nanocrystals have generated tremendous interest because of their solution processability and robust tunability. Among such nanocrystals, the colloidal quantum dot (CQD) draws the most attention for its well-known quantum size effects. In the last decade, applications of CQDs have been booming in electronics and optoelectronics, especially in photovoltaics. Electronically doped semiconductors are critical in the fabrication of solar cells, because carefully designed band structures are able to promote efficient charge extraction. Unlike conventional semiconductors, diffusion and ion implantation technologies are not suitable for doping CQDs. Therefore, researchers have creatively developed alternative doping methods for CQD materials and devices. In order to provide a state-of-the-art summary and comprehensive understanding to this research community, we focused on various doping techniques and their applications for photovoltaics and demystify them from different perspectives. By analyzing two classes of CQDs, lead chalcogenide CQDs and perovskite CQDs, we compared different working scenarios of each technique, summarized the development in this field, and raised our own future perspectives.
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Beard, Matt C. "(Invited) Ultrafast Spectroscopy Measurements of Lead-Halide Hybrid Semiconductor Nanocrystals for Photocatalysis." ECS Meeting Abstracts MA2022-02, no. 48 (October 9, 2022): 1831. http://dx.doi.org/10.1149/ma2022-02481831mtgabs.
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We are exploring the use of metal-halide perovskite semiconductor nanocrystals (PNCs) as efficient photocatalysis. Heterogeneous photocatalysis are less common than homogeneous but can provide unique avenues for inducing novel chemical transformations and can also be utilized for energy transductions, i.e., the energy in the photons can be captured in chemical bonds. Additional, earth abundant nanocrystal based photocatalyst are highly sought after as they can potentially eliminate expensive noble metal catalyst. A detailed understand of the underlying reaction mechanism could provide guidance in designing new systems that can activate a larger class of small molecules. Here, we discuss transient absorption spectroscopy to study a model C-C bond formation reaction, i.e., alkylation of aldehydes catalyzed by colloidal CsPbBr3 NCs. We find that both electrons and holes undergo ultrafast charge transfer from photoexcited PNCs. After charge transfer the charge separated state lives ~ 1 ns enabling radical mechanism to form C-C bonds. I will also discuss the use of PNCs to host a transition metal Cu-site incorporated at the surface of the PNCs to induce a to induce a N-N heterocyclization reaction. The reaction starts from surface coordinated diamine substrates and requires to subsequent photo-oxidation events. We established a photocatalytic cycle where photo-excited holes are funneled to the coordinated substrates.
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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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Zhou, Qingchao, and Zhongyi Shang. "CuInS2 Nanocrystals Embedded PMMA Composite Films: Adjustment of Polymer Molecule Weights and Application in Remote-Type White LEDs." Nanomaterials 13, no. 6 (March 17, 2023): 1085. http://dx.doi.org/10.3390/nano13061085.
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The commercial application of colloidal semiconductor nanocrystals has been realized owing to the development of composite film technology. Here, we demonstrated the fabrication of green and red emissive CuInS2 nanocrystals embedded polymer composite films of equal thickness by using a precise solution casting method. The impacts of polymer molecular weight on the dispersibility of CuInS2 nanocrystals were then systematically studied through evaluating the decrease in transmittance and red shift of emission wavelength. The composite films made from PMMA of small molecular weights exhibited higher transmittance. Applications of these green and red emissive composite films as color converters in remote-type light-emitting devices were further demonstrated.
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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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Wu, Fengbing, Dawei Zhang, Shuzhen Shang, Yiming Zhu, Songlin Zhuang, and Jian Xu. "Developing Quantum Dot Phosphor-Based Light-Emitting Diodes for Aviation Lighting Applications." Journal of Nanomaterials 2012 (2012): 1–5. http://dx.doi.org/10.1155/2012/629157.
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We have investigated the feasibility of employing quantum dot (QD) phosphor-based light-emitting diodes (LEDs) in aviation applications that request Night Vision Imaging Systems (NVIS) compliance. Our studies suggest that the emerging QD phosphor-based LED technology could potentially be superior to conventional aviation lighting technology by virtue of the marriage of tight spectral control and broad wavelength tunability. This largely arises from the fact that the optical properties of semiconductor nanocrystal QDs can be tailored by varying the nanocrystal size without any compositional changes. It is envisioned that the QD phosphor-based LEDs hold great potentials in cockpit illumination, back light sources of monitor screens, as well as the LED indicator lights of aviation panels.
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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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Himadri, D., D. Pranayee, and S. Kandarpa Kumar. "Synthesis of PbS Nanoparticles and Its Potential as a Biosensor based on Memristic Properties." Volume 4,Issue 5,2018 4, no. 5 (September 14, 2018): 500–502. http://dx.doi.org/10.30799/jnst.147.18040510.
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Quantum dots are nearly spherical nanocrystals that have unique optical property which are in intermediate in size between bulk semiconductor and individual atom. Lead sulphide (PbS) nanoparticles are synthesized by the reaction between lead nitrate and sodium sulphide. This paper proposes a detection method of bacterial sample based on memristic properties of semiconductor quantum dots. In this case, PbS nanoparticle is considered for its good fluorescent property. PbS nanoparticle were synthesized and characterized by UV –visible spectroscopy, PL, XRD, SEM and HRTEM. The antimicrobial activity of Pbs and CdS quantum dots are observed in this paper. The potential application of these quantum dots as a biosensor is examined by conjugating bacterial stain E. coli and S. aureus and examining the current –voltage characteristics with E. coli.
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Kamat, Prashant V., Rebecca Scheidt, Geetha Balakrishna, Steven Kobosko, and Vikashkumar Ravi. "(Keynote) Photocatalytic Aspects of CsPbBr3 Perovskite Nanocrystals." ECS Meeting Abstracts MA2018-01, no. 31 (April 13, 2018): 1842. http://dx.doi.org/10.1149/ma2018-01/31/1842.
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Lead halide perovskites have been extensively studied to explore their photovoltaic properties. They offer a useful strategy for continuous tuning of the semiconductor bandgap. In addition to photovoltaic applications these lead halide perovskites offer rich photophysical properties with ability to induce electron and hole transfer at the semiconductor/electrolyte interface. The photoinduced electron transfer between CsPbBr3 quantum dots and methyl viologen shows electron transfer to be completed with 20 ps. The transient absorption spectroscopy and emission spectroscopy offers mechanistic and kinetic insights of the interfacial charge transfer processes. CsPbBr3 films cast from colloidal suspension can also be transformed into CsPbI3 via a halide exchange reaction upon exposure to a heated PbI2 solution (~70°C). The internal structure of hybrid CsPbBrxI3-x varies with increasing thickness of the exchanged film. The gradient structure thus allows us to probe the flow of the charge carriers within the film. The electron transfer properties that highlight photocatalytic properties of mixed halide nanocrystals will be discussed.
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Gutman, Nadav, Akiva Armon, Michael Shandalov, Anna Osherov, Yuval Golan, and Amir Sa'ar. "Silicon Photonic Crystals Doped with Colloidally Synthesized Lead Salt Semiconductors Nanocrystals." Journal of Nanoscience and Nanotechnology 9, no. 6 (June 1, 2009): 3648–51. http://dx.doi.org/10.1166/jnn.2009.ns45.
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Yang, Shihe, Suhua Wang, and K. K. Fung. "One-dimensional growth of rock-salt PbS nanocrystals mediated by surfactant/polymer templates." Pure and Applied Chemistry 72, no. 1-2 (January 1, 2000): 119–26. http://dx.doi.org/10.1351/pac200072010119.
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A novel method has been developed for the synthesis of compound semiconductor nanorods (PbS). This method consists of using a functionalized lead(II) salt Pb(AOT)2 as the precursor and a polymer (PVB) as both a matrix and a stabilizer. The PbS nanocrystallites prepared using this method are all oriented with their (100) lattice planes parallel to the substrate surface. Possible mechanisms are briefly discussed for the growth of the rod-shaped PbS nanocrystals with the preferred orientation in the polymer film.
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Schrier, Joshua, Byounghak Lee, and Lin-Wang Wang. "Mechanical and Electronic-Structure Properties of Compressed CdSe Tetrapod Nanocrystals." Journal of Nanoscience and Nanotechnology 8, no. 4 (April 1, 2008): 1994–98. http://dx.doi.org/10.1166/jnn.2008.18264.
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The coupling of mechanical and optical properties in semiconductor nanostructures can potentially lead to new types of devices. This work describes our theoretical examination of the mechanical properties of CdSe tetrapods under directional forces, such as may be induced by AFM tips. In addition to studying the general behavior of the mechanical properties under modifications of geometry, nanocrystal-substrate interaction, and dimensional scaling, our calculations indicate that mechanical deformations do not lead to large changes in the band-edge state eigenenergies, and have only a weak effect on the oscillator strengths of the lowest energy transitions.
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Harris-Lee, Thom R., Yan Zhang, Christopher R. Bowen, Philip J. Fletcher, Yuanzhu Zhao, Zhenyu Guo, Jerome W. F. Innocent, S. Andrew L. Johnson, and Frank Marken. "Photo-Chlorine Production with Hydrothermally Grown and Vacuum-Annealed Nanocrystalline Rutile." Electrocatalysis 12, no. 1 (November 9, 2020): 65–77. http://dx.doi.org/10.1007/s12678-020-00630-x.
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AbstractPhoto-generated high-energy surface states can help to produce chlorine in aqueous environments. Here, aligned rutile (TiO2) nanocrystal arrays are grown onto fluorine-doped tin oxide (FTO) substrates and activated either by hydrothermal Sr/Ba surface doping and/or by vacuum-annealing. With vacuum-annealing, highly photoactive films are obtained with photocurrents of typically 8 mA cm−2 at 1.0 V vs. SCE in 1 M KCl (LED illumination with λ = 385 nm and approx. 100 mW cm−2). Photoelectrochemical chlorine production is demonstrated at proof-of-concept scale in 4 M NaCl and suggested to be linked mainly to the production of Ti(III) surface species by vacuum-annealing, as detected by post-catalysis XPS, rather than to Sr/Ba doping at the rutile surface. The vacuum-annealing treatment is proposed to beneficially affect (i) bulk semiconductor TiO2 nanocrystal properties and electron harvesting, (ii) surface TiO2 reactivity towards chloride adsorption and oxidation, and (iii) FTO substrate performance.
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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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Wang, Xiaoqian, Wanli Liu, Jiazhen He, Yuqing Li, and Yong Liu. "Synthesis of All-Inorganic Halide Perovskite Nanocrystals for Potential Photoelectric Catalysis Applications." Catalysts 13, no. 7 (June 27, 2023): 1041. http://dx.doi.org/10.3390/catal13071041.
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Compared with conventional semiconductors, halide perovskite nanocrystals (NCs) have a unique crystal structure and outstanding optoelectronic properties, offering wide potential for applications in optoelectronic devices such as solar cells, photodetectors, light-emitting diodes, lasers, and displays. Rational technological design is providing vital support for the development of perovskite optoelectronics. Herein, monodisperse all-inorganic halide perovskite nanocrystals with consistent morphology and cubic crystal phase were synthesized employing a modified one-pot hot injection method to independently modulate the stoichiometric ratios of three precursors involving cesium salt, lead source, and halide. In combination with an anion exchange reaction, mixing two kinds of perovskite NCs with different halogens enables a transition from violet emission to green and finally to red emission over the entire visible region. Additionally, optical and electrochemical tests suggested that the as-synthesized halide perovskite NCs are promising for photoelectric catalysis applications.
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Erce-Montilla, R., M. PiÑero, N. de la Rosa-Fox, A. Santos, and L. Esquivias. "Control growth of PbS quantum dots doped sono-ormosil." Journal of Materials Research 16, no. 9 (September 2001): 2572–78. http://dx.doi.org/10.1557/jmr.2001.0353.
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Semiconductor PbS quantum dots doped-SiO2 organically modified silicate (ormosil) gels were synthesised via sol-gel by using high-power ultrasounds (sonogel). The effect of PbS crystal concentration and the addition of (3-mercaptopropyl)trimethoxysilane acting as surface capping agent (SCA) were investigated. By adjustment of the SCA to lead ratio, PbS nanoparticles of different sizes and morphologies were obtained. Textural parameters were calculated from N2 physisorption isotherms. The PbS galena phase was identified by x-ray diffraction, the crystal size by high-resolution transmission electron microscopy, and the exciton confinement by ultraviolet–visible–near-infrared spectrophotometry. Crystallite mean sizes of spheres and cubes ranging from 6.5 to 10.5 nm and needles 7-nm wide and 15–20 nm long, for different PbS and SCA concentrations, were obtained. These results differ from those predicted by the effective mass approximation corroborating the band gap modifications in the smallest nanocrystals. The method allows the control of the crystal size and improves the stabilization of the PbS nanocrystals.
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Boudjemila L., Aleshin A. N., Malyshkin V. M., Aleshin P. A., Shcherbakov I. P., Petrov V. N., and Terukov E. I. "Electrical and Optical Characteristics of CsPbI-=SUB=-3-=/SUB=- and CsPbBr-=SUB=-3-=/SUB=- Lead Halide Perovskite Nanocrystal Films Deposited on c-Si Solar Cells for Photovoltaic Applications." Physics of the Solid State 64, no. 11 (2022): 1670. http://dx.doi.org/10.21883/pss.2022.11.54189.418.
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The deposition of an additional layer of nanoparticles is a widely used method for improving the optical and electrical characteristics of semiconductor solar cells (SCs). In this work, films of nanocrystals (NC) of inorganic perovskites of lead halides CsPbI3 and CsPbBr3 are deposited on the surface of a solar cell based on crystalline silicon (c-Si). It is shown that the optical properties of such NC films are in good agreement with the optical properties of c-Si. It has been found that the absorption coefficient of solar cells with NC layers of inorganic perovskites is much higher in the visible region of the spectrum, which increases the photocurrent generation in the SC in the range of 370-900 nm. A significant effect of surface roughness on the photoelectric properties of solar cells has been found. CsPbI3 NC films have a textured surface and higher photocurrent than CsPbBr3 NC films, which are rougher. Enhanced photovoltaic properties of photoelectric structures with a CsPbI3 NC layer compared to CsPbBr3 NC films due to their lower degree of roughness were observed. Keywords: perovskite nanocrystals, silicon solar cells, reflection spectra, photoluminescence, electrical conductivity.
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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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Lingley, Zachary, Krishnamurthy Mahalingam, Siyuan Lu, Gail J. Brown, and Anupam Madhukar. "Nanocrystal-semiconductor interface: Atomic-resolution cross-sectional transmission electron microscope study of lead sulfide nanocrystal quantum dots on crystalline silicon." Nano Research 7, no. 2 (December 21, 2013): 219–27. http://dx.doi.org/10.1007/s12274-013-0389-4.
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Ko, Dong-Kyun, Junsung Park, Mohammad M. Al Mahfuz, and Rock Huebner. "Mid-Infrared Photoconductive Detectors Fabricated from Solution-Processed PbSe Nanocrystals." ECS Meeting Abstracts MA2022-02, no. 20 (October 9, 2022): 921. http://dx.doi.org/10.1149/ma2022-0220921mtgabs.
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Lead selenide (PbSe) was the first semiconductor used for photosensors operating in the mid-wavelength infrared spectral region (3-5 um) and is still the primary choice for low-cost, uncooled photoconductive detector applications. Even through PbSe has been studied for over 70 years, more understandings on its physical mechanism for high photoresponsivity is still emerging. Common methods of fabricating PbSe detectors involve physical/chemical vapor deposition or chemical bath deposition (CBD) techniques, followed by post-deposition sensitization processes including oxygen annealing and iodization. Here, we present a new approach to fabricating photoconductive devices based on PbSe colloidal nanocrystals. This infrared colloidal ink can serve as a critical component to enabling digital additive manufacturing of mid-infrared sensor arrays and simultaneously lower the fabrication cost by removing multiple masking steps required in conventional approaches. We report on the synthesis and fabrication of PbSe nanostructured film and the effects of thermal annealing as well as oxygen and iodide incorporation on the photoconductive properties.
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González-Rubio, Guillermo, and Wiebke Albrecht. "Engineering of plasmonic gold nanocrystals through pulsed laser irradiation." Applied Physics Letters 121, no. 20 (November 14, 2022): 200502. http://dx.doi.org/10.1063/5.0122888.
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Gold nanocrystals (NCs) have drawn tremendous interest in the scientific community due to their unique ability to interact with light. When irradiated with ultrafast pulsed lasers, the lattice temperature of gold NCs can rapidly increase, even above the melting and evaporation thresholds, which results in strong morphological, structural, and aggregation state modifications. Thereby, ultrafast pulsed laser irradiation can lead to the formation of metastable gold nanostructures with distinctive physicochemical features. In this Perspective, we discuss the implementation of femtosecond and nanosecond pulsed lasers to engineer gold NCs. We underline the importance of controlling the heating and cooling dynamics to achieve desired reshaping and restructuring of gold NCs at temperatures below and above its melting point. In addition, we demonstrate the need for advanced electron microscopy characterization techniques and single-particle studies to understand the detailed atomistic mechanisms behind the modifications following pulsed laser irradiation. Finally, we provide our views of the evolving opportunities of ultrafast laser irradiation as a unique tool for the fabrication of unprecedented nanomaterials and catalysts from metal and multimetal NCs to semiconductors.
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He, Ziyang, Huan Liu, Fei Xie, Mingyu Bai, Shuai Wen, Jijie Zhao, and Weiguo Liu. "Lead Selenium Colloidal Quantum Dots for 400-2600 nm Broadband Photodetectors." Journal of Nanomaterials 2022 (February 4, 2022): 1–8. http://dx.doi.org/10.1155/2022/2940382.
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By the photodetector manufactured using traditional semiconductor materials, such as HgCdTe and InGaAs, it is difficult to broaden the application range of such photodetectors due to their high cost and complex manufacturing process. PbSe colloidal quantum dots (CQDs) have the potential to shift the working range of photodetector from visible to infrared wavelength region, and it also has high photoresponsivity. Herein, we report the characterization of PbSe CQDs synthesized using a facile solution process, as well as the relationship between the size of nanocrystal and the reaction temperature. The films of PbSe CQDs are deposited using the layer-by-layer (LbL) spin-coating method, which is then used to fabricate the photoconductive device. The fabricated device is found to have an efficient response in a broad spectrum range of 400-2600 nm. The device maintains good responsivity of ~320 mA/W at room temperature. Its external quantum efficiency was quite high in the shorter wavelength infrared region, and it has approximately 14% external quantum efficiency (EQE) at 2520 nm. The device demonstrated excellent performance, confirming that PbSe colloidal quantum dots is a promising material for future broadband spectrum photodetectors.
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Emin, Saim, Ceco Dushkin, Seiichiro Nakabayashi, and Eiki Adachi. "Growth kinetics of CdSe nanoparticles synthesized in reverse micelles using bis(trimethylsilyl) selenium precursor." Open Chemistry 5, no. 2 (June 1, 2007): 590–604. http://dx.doi.org/10.2478/s11532-007-0018-8.
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AbstractWe first focus on the kinetics of nanoparticle growth in a microemulsion synthesis of CdSe semiconductor nanocrystals. The process consists of a fast initial stage of typical time constant of the order of 103 s followed by a slow stage of time constant of the order of 104s. Growth proceeds similarly to that described for the hot-matrix synthesis of CdSe, underlining the generality of the two-stage growth mechanism, irrespective of the matrix type and synthesis conditions. However, the time constant of each stage in the microemulsion synthesis is much larger than in the hot-matrix one. Also, the ratio between the fast and slow time constant is appreciably bigger. We also prove that larger size reverse micelles, obtained by increasing the water:surfactant ratio, generally lead to larger CdSe nanoparticles. Bis(trimethylsilyl) selenium is the crucial precursor for the CdSe nanoparticle synthesis. An intermediate stage of the chemical reaction limiting the bis(trimethylsilyl) selenium production is described theoretically.
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Creutz, Sidney E., Evan N. Crites, Michael C. De Siena, and Daniel R. Gamelin. "Colloidal Nanocrystals of Lead-Free Double-Perovskite (Elpasolite) Semiconductors: Synthesis and Anion Exchange To Access New Materials." Nano Letters 18, no. 2 (February 5, 2018): 1118–23. http://dx.doi.org/10.1021/acs.nanolett.7b04659.
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Aceves-Mijares, M., A. A. González-Fernández, R. López-Estopier, A. Luna-López, D. Berman-Mendoza, A. Morales, C. Falcony, C. Domínguez, and R. Murphy-Arteaga. "On the Origin of Light Emission in Silicon Rich Oxide Obtained by Low-Pressure Chemical Vapor Deposition." Journal of Nanomaterials 2012 (2012): 1–11. http://dx.doi.org/10.1155/2012/890701.
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Silicon Rich Oxide (SRO) has been considered as a material to overcome the drawbacks of silicon to achieve optical functions. Various techniques can be used to produce it, including Low-Pressure Chemical Vapor Deposition (LPCVD). In this paper, a brief description of the studies carried out and discussions of the results obtained on electro-, cathode-, and photoluminescence properties of SRO prepared by LPCVD and annealed at 1,100°Care presented. The experimental results lead us to accept that SRO emission properties are due to oxidation state nanoagglomerates rather than to nanocrystals. The emission mechanism is similar to Donor-Acceptor decay in semiconductors, and a wide emission spectrum, from 450 to 850 nm, has been observed. The results show that emission is a function of both silicon excess in the film and excitation energy. As a result different color emissions can be obtained by selecting the suitable excitation energy.
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Menezes, Shalini, Anura P. Samantilleke, Sharmila J. Menezes, Yi Mo, and David S. Albin. "Electrodeposition of poly and nanocrystalline Cu-In-Se absorbers for optoelectronic devices." MRS Advances 4, no. 37 (2019): 2043–52. http://dx.doi.org/10.1557/adv.2019.319.
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ABSTRACTCoupling semiconductors with electrochemical processes can lead to unusual materials, and attractive, practical device configurations. This work examines the reaction mechanism for single-step electrodeposition approach that creates device quality copper-indium-selenide (CISe) films with either polycrystalline or nanocrystalline morphologies on Cu and steel foils, respectively. The polycrystalline CISe film grows from In3+/Se4+ solution on Cu foil as Cu→ CuxSe→ CuInSe2; it may be used in standard planar pn devices. The nanocrystalline CISe film grown from Cu+/In3+/Se4+ solution follows the CuSe(In)→ CuInSe2→ CuIn3Se5 sequence. The latter approach leads to naturally ordered, space-filling nanocrystals, comprising interconnected 3-dimensional network of sharp, abrupt, p-CISe/n-CISe bulk homojunctions with extraordinary electro-optical attributes. Sandwiching these films between band-aligned contact electrodes can lead to high performance third generation devices for solar cells, light emitting diodes or photoelectrodes for fuel cells. Both approaches produce self-stabilized CISe absorbers that avoid recrystallization steps and can be roll-to-roll processed in simple flexible thin-film form factor for easy scale-up.
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McCluskey, Matthew D., Marianne C. Tarun, and Samuel T. Teklemichael. "Acceptor Dopants in Bulk and Nanoscale ZnO." MRS Proceedings 1494 (2012): 3–12. http://dx.doi.org/10.1557/opl.2012.1574.
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ABSTRACTZinc oxide (ZnO) is a semiconductor that emits bright UV light, with little wasted heat. This intrinsic feature makes it a promising material for energy-efficient white lighting, nano-lasers, and other optical applications. For devices to be competitive, however, it is necessary to develop reliable p-type doping. Although substitutional nitrogen has been considered as a potential p-type dopant for ZnO, recent theoretical and experimental work suggests that nitrogen is a deep acceptor and will not lead to p-type conductivity. In nitrogen-doped samples, a red photoluminescence (PL) band is correlated with the presence of deep nitrogen acceptors. PL excitation (PLE) measurements show an absorption threshold of 2.26 eV, in good agreement with theory. The results of these studies seem to rule out group-V elements as shallow acceptors in ZnO, contradicting numerous reports in the literature. Optical studies on ZnO nanocrystals show some intriguing leads. At liquid-helium temperatures, a series of sharp IR absorption peaks arise from an unknown acceptor impurity. The data are consistent with a hydrogenic acceptor 0.46 eV above the valence band edge. While this binding energy is still too deep for many practical applications, it represents a significant improvement over the 1.4-1.5 eV binding energy for nitrogen acceptors. Nanocrystals present another twist. Due to their high surface-to-volume ratio, surface states are especially important. In our model, the 0.46 eV level is shallow with respect to the surface valence band, raising the possibility of surface hole conduction.
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Tahara, Hirokazu, and Yoshihiko Kanemitsu. "(Invited, Digital Presentation) Photocurrent Detection of Cooperative Exciton Quantum Interference in Nanocrystal Thin Films." ECS Meeting Abstracts MA2022-02, no. 20 (October 9, 2022): 922. http://dx.doi.org/10.1149/ma2022-0220922mtgabs.
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Colloidal semiconductor quantum dots (QDs) are excellent materials for studying the photophysics of exciton complexes such as biexcitons, triexcitons, and charged excitons (trions). Dynamics of exciton complexes usually determines the performance of optoelectronic devices [1]. For example, trions reduce the optical gain threshold in QD lasers and multiexcitons increase photon-to-current conversion efficiencies via carrier multiplication processes in QD solar cells. In addition, unconventional properties of multiexcitons emerge in coherent processes in QD systems. We recently discovered the high-frequency coherent oscillations with integer multiples of the exciton resonance frequency, which is called multiexciton harmonic quantum coherence [2,3]. The multiexciton coherent properties have been investigated using optical methods. However, to clarify their roles in optoelectronic devices, it is necessary to conduct the electrical detection of multiexciton coherence. Here, we performed photocurrent detection of exciton quantum interference signals in QD thin films. The samples used in this study were closely packed PbS QD thin films. The QD films were sandwiched between the electron and hole transport layers to extract photogenerated carriers. Multiexcitons were generated by phase-locked femtosecond laser pulses, and then their photocurrent quantum interference signals were measured by using a quantum interference technique [4]. The photocurrent interference signal in the weak excitation shows a single sinusoidal oscillation originating from single excitons, while the interference signal changes to the profile involving multiple sinusoidal oscillations with increasing excitation intensity. This means that the multiexciton quantum coherence exhibiting harmonic oscillations is successfully detected in a photocurrent technique [5]. Furthermore, the amplitudes of harmonic quantum coherent signals in coupled QDs are significantly larger than those in isolated QDs. We clarified that the enhancement of the amplitudes is caused by cooperative processes in coupled QDs, where excitons in adjacent QDs interact with each other through their inter-QD coherent coupling. This cooperative effect can provide a new way to use inter-QD coherent coupling in advanced optoelectronic applications, e.g., amplifiers of coherent signals. Part of this work was supported by JSPS KAKENHI (JP19H05465 and JP22H01990) and JST CREST (JPMJCR21B4). References [1] Kanemitsu, Y. Trion dynamics in lead halide perovskite nanocrystals. J. Chem. Phys. 151, 170902 (2019). [2] Tahara, H.; Sakamoto, M.; Teranishi, T.; Kanemitsu, Y. Harmonic Quantum Coherence of Multiple Excitons in PbS/CdS Core-Shell Nanocrystals. Phys. Rev. Lett. 119, 247401 (2017). [3] Tahara, H.; Sakamoto, M.; Teranishi, T.; Kanemitsu, Y. Quantum coherence of multiple excitons governs absorption cross-sections of PbS/CdS core/shell nanocrystals. Nat. Commun. 9, 3179 (2018). [4] Tahara, H.; Kanemitsu, Y. Quantum Interference Measurements and Their Application to Analysis of Ultrafast Photocarrier Dynamics in Semiconductor Solar Cell Materials. Adv. Quantum Technol. 3, 1900098 (2020). [5] Tahara, H.; Sakamoto, M.; Teranishi, T.; Kanemitsu, Y. Collective enhancement of quantum coherence in coupled quantum dot films. Phys. Rev. B 104, L241405 (2021).
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Буджемила, Л., А. Н. Алешин, В. Г. Малышкин, П. А. Алешин, И. П. Щербаков, В. Н. Петров, and Е. И. Теруков. "Электрические и оптические характеристики пленок нанокристаллов перовскитов галогенида свинца CsPbI-=SUB=-3-=/SUB=- и CsPbBr-=SUB=-3-=/SUB=-, нанесенных на c-Si солнечные элементы для фотовольтаических приложений." Физика твердого тела 64, no. 11 (2022): 1695. http://dx.doi.org/10.21883/ftt.2022.11.53322.418.
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The deposition of an additional layer of nanoparticles is a widely used method for improving the optical and electrical characteristics of semiconductor solar cells (SCs). In this work, films of nanocrystals (NC) of inorganic perovskites of lead halides CsPbI3 and CsPbBr3 are deposited on the surface of a solar cell based on crystalline silicon (c-Si). It is shown that the optical properties of such NC films are in good agreement with the optical properties of c-Si. It has been found that the absorption coefficient of solar cells with NC layers of inorganic perovskites is much higher in the visible region of the spectrum, which increases the photocurrent generation in the SC in the range of 370–900 nm. A significant effect of surface roughness on the photoelectric properties of solar cells has been found. CsPbI3 NC films have a textured surface and higher photocurrent than CsPbBr3 NC films, which are rougher. Enhanced photovoltaic properties of FE structures with a CsPbI3 NC layer compared to CsPbBr3 NC films due to their lower degree of roughness were observed.
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Mishra, Leepsa, Aradhana Panigrahi, Priyanka Dubey, and Manas Kumar Sarangi. "Photo-induced charge transfer in composition-tuned halide perovskite nanocrystals with quinone and its impact on conduction current." Journal of Applied Physics 132, no. 19 (November 21, 2022): 195702. http://dx.doi.org/10.1063/5.0123558.
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A facile interfacial charge transfer (CT) with a reduced inter-layer energy band regulates the charge transport mechanism in any optoelectronic device. The enhancement in semiconductor-based device performance often demands improved CT dynamics and collection of free carriers with reduced charge recombination. In this work, we present a detailed inspection of the photo-induced CT between inorganic lead halide perovskite nanocrystals (PNCs) with varied compositions and their consequence on the charge transport process. The superior CT rate in mixed halide CsPbBr2Cl PNCs with naphthoquinone (NPQ) is revealed when compared with the parent CsPbBr3 PNCs and its anion-exchanged counterpart CsPbCl3. The glimpses of hole transfer contribution along with electron transfer are detected for CsPbBr2Cl with superior CT efficiency. The enhanced conduction current after the insertion of NPQ into the PNCs with a reduced hysteresis suggests an improved charge transport in the fabricated device compared to the pristine PNCs. These findings can contribute to a better understanding of multiple ways of engineering optoelectronic devices to boost performance and efficiencies and the concurrent role of the CT process in the conduction mechanism.
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König, Dirk, and Sean C. Smith. "Analytical description of nanowires. I. Regular cross sections for zincblende and diamond structures." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 75, no. 5 (September 3, 2019): 788–802. http://dx.doi.org/10.1107/s2052520619009351.
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Semiconductor nanowires (NWires) experience stress and charge transfer from their environment and impurity atoms. In response, the environment of a NWire experiences a NWire stress response which may lead to propagated strain and a change in the shape and size of the NWire cross section. Here, geometric number series are deduced for zincblende- (zb-) and diamond-structured NWires of diameter d Wire to obtain the numbers of NWire atoms N Wire(d Wire[i]), bonds between NWire atoms N bnd(d Wire[i]) and interface bonds N IF(d Wire[i]) for six high-symmetry zb NWires with the low-index faceting that occurs frequently in both bottom-up and top-down approaches of NWire processing. Along with these primary parameters, the specific lengths of interface facets, the cross-sectional widths and heights and the cross-sectional areas are presented. The fundamental insights into NWire structures revealed here offer a universal gauge and thus could enable major advancements in data interpretation and understanding of all zb- and diamond-structure-based NWires. This statement is underpinned with results from the literature on cross-section images from III–V core–shell NWire growth and on Si NWires undergoing self-limiting oxidation and etching. The massive breakdown of impurity doping due to self-purification is shown to occur for both Si NWires and Si nanocrystals (NCs) for a ratio of N bnd/N Wire = N bnd/N NC = 1.94 ± 0.01 using published experimental data.
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Mahmoud Idris Mohammed, Ahmed. "Halide and Oxide Double Perovskites As Promising Semiconductor Photocatalysts Candidates for Artificial Photosynthesis of Solar Fuels." ECS Meeting Abstracts MA2022-02, no. 48 (October 9, 2022): 1856. http://dx.doi.org/10.1149/ma2022-02481856mtgabs.
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Abstract Artificial photosynthesis of solar fuels is deemed as one of the Holy grails of renewable energy technology for simultaneously solving energy and environmental issues. At the present, it is one of the most involved programs in the international Mission Innovation Challenge for Accelerating the Clean Energy Revolution. Solar-driven water splitting and CO2 conversion are the main research application of artificial photosynthesis. However, these reactions are extremely challenging due to energetically uphill (G>0) and non-spontaneous multi-electron transfer processes, which are difficult to be understood by traditional knowledge of catalysis. An efficient solar energy conversion system must simultaneously deal well with light absorption, charge separation and transfer, surface redox reactions. Particularly, efficient charge separation and transfer by retarding back electron transfer, are often regarded as the key determining steps for overall solar energy conversion. To solve the high recombination rates of photogenerated electron-hole pairs and their low reduction and oxidation abilities in a single photocatalyst, heterojunction manipulation is urgently required. Two mainstream heterojunctions—type-II and Z-scheme heterojunctions have been widely acknowledged [1]. Recently, lead halide perovskites (LHPs) with the chemical formula of ABX3, where A is an organic or inorganic cation (A= Cs+, MA+, FA+), B is Pb2+, and X is a halogen anion (Br-, Cl-, I-), such as CH3NH3PbI3,FAPbI3, and CsPbBr3 have been widely investigated as auspicious semiconductor photocatalysts for photocatalytic H2 production and photocatalytic CO2 reduction owing to their impressive photoelectrochemical properties, facile to synthesize, high carrier mobility, low exciton binding energy, and long carrier lifetime [2]. However, the high toxicity and notorious instability upon exposure to light, moisture, and high temperature are the major obstacles to their practical use.Therefore, developing alternative lead-free semiconductor photocatalysts with similar optoelectronic properties to the LHPs is highly needed. Inorganic halide double-perovskites and analogous oxide double-perovskites with the chemical formula of A2B'B"X6 and A2B'B"O6, respectively, are layered 3D materials, which have been considered as a novel ecofriendly visible light responsive semiconductor photocatalysts to replace the toxic lead-halide perovskite. The main feature of the halide and oxide double-perovskites is that their structures can be accommodated with different transition metal combinations on B' and B" site cations to tune their intrinsic properties such as light absorption, carrier mobilities, chemical diversity, and so on. Theoretically, an auspicious photocatalytic activity can be realized from them owing to their impressive photophysical properties. However, poor charge separation and severe charge recombination have restricted their practical photocatalytic application. Recently, several halides and oxides double perovskites have been demonstrated as visible light-responsive photocatalysts for photocatalytic CO2 reduction and photocatalytic half-reaction (oxygen and hydrogen evolution reactions) such as Cs2AgBrBr6, Cs2AgSbBr6, Sr2CoTaO6, Sr2CoWO6, etc. [3-5]. However, for oxide double perovskites even though they have shown bifunctional photocatalytic oxygen and hydrogen two half-reactions with visible light but their potential as photocatalytic CO2 reduction and one-step overall water splitting have not been achieved so far. Therefore, further improvement of the material design and synthesis by assembling heterostructure based on two eco-friendly halide and oxide double perovskites may play a key role in achieving high efficient photocatalytic performance under visible-light-irradiation. Thought is a challenging task, but holds great potential in advancing science and technology in photocatalysis. References Liao, C. Li, S.-Y. Liu, B. Fang, H. Yang, Emerging frontiers of Z-scheme photocatalytic systems, Trends in Chemistry. 4 (2022) 111–127. -C. Wang, N. Li, A.M. Idris, J. Wang, X. Du, Z. Pan, Z. Li, Surface Defect Engineering of CsPbBr3 Nanocrystals for High Efficient Photocatalytic CO2 Reduction, Solar RRL. 5 (2021) 2100154. Idris, A. M.; Liu, T.; Shah, J. H.; Zhang, X.; Ma, C.; Malik, A. S.; Jin, A. Solar RRL 2020, 4 (3), 1900456. Idris, A. M.; Liu, T.; Hussain Shah, J.; Han, H.; Li, C. ACS Sustainable Chemistry&Engineering 2020, 8 (37), 14190-14197. Wang, H. Huang, Z. Zhang, C. Wang, Y. Yang, Q. Li, D. Xu, Lead-free perovskite Cs2AgBiBr6@g-C3N4 Z-scheme system for improving CH4 production in photocatalytic CO2 reduction, Applied Catalysis B: Environmental. 282 (2021).
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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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Kuo, Yue. "(Edward G. Acheson Award) Exploration of Amorphous Thin Film Electronics." ECS Meeting Abstracts MA2022-02, no. 15 (October 9, 2022): 2409. http://dx.doi.org/10.1149/ma2022-02152409mtgabs.
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Thin films are critical elements in modern semiconductor devices. They are often prepared in the amorphous phase due to practical reasons, such as the reliability and manufacturability concerns. For example, the amorphous high-k gate dielectric is less prone to current leakage than the polycrystalline dielectric in the MOS device (1). The utilization of amorphous silicon (a-Si:H) or metal oxide semiconductor layer enables the commercial production of thin film transistor (TFT) arrays for flat panel displays (2). Requirements for amorphous thin films are related to the products. For advanced MOSFETs, the nanometer EOT gate dielectric is necessary (3). For LCD or OLED TVs or monitors, the fabrication process has to be low temperature, large area capability, and high throughput (4). In addition, the fabricated device has to be highly reliable, i.e., resistant to damages from subsequent process steps and environmental exposure. In this talk, examples on amorphous thin films conducted in my group will be given and discussed. The doped metal oxide high-k thin film, which has a crystallization temperature higher than that of the undoped film (5), will be examined with respect to fundamental material and electrical properties. Novel devices made from this kind of film, e.g., nanocrystals embedded nonvolatile memories (6) and nano-resistor solid state incandescent LEDs (SSI-LEDs) (7), will be shown and the principles will be deliberated. Separately, PECVD process condition affects the a-Si:H TFT performance as well as the uniformity of the large-area material properties (8), which can be explained with the generalized deposition-etching mechanism (9). Applications of a-Si:H TFTs in nonvolatile memories, e.g., using the floating-gate structure (10), and protein/DNA analysis, e.g., attached with the microchannel device (11), will also be examined. In order to achieve the best device performance with high reliability, both the bulk film and the interface properties of the amorphous thin film have to be tightly controlled, which requires the multidisciplinary approach. This is the early stage of the field. Many new and unique applications of the amorphous thin films can be expected in the near future. Y. Kuo, ECS Trans., 54(1), 273-281 (2013). Y. Kuo, Amorphous Silicon Thin Film Transistors, Kluwer, Norwell, MA, 2004. J. Yan, Y. Kuo, and J. Lu, Electrochem. Solid-State Lett., 10(7), H199-H202 (2007). Y. Kuo, ECS Interface, 22(1), 55-60 (2013). J.-Y. Tewg, Y. Kuo, and J. Lu, Electrochem. Solid-State Lett., 8(1), G27-G29 (2005). Y. Kuo, ECS Trans., 3(3), 253-263 (2006). Y. Kuo and C.-C. Lin, Appl. Phys. Letts., 102(3), 031117 (2013). Y. Kuo, J. Electrochem. Soc., 142, 186-190 (1995). Y. Kuo, Appl. Phys. Lett., 63(2), 144-146 (1993). Y. Kuo and H. Nominanda, Appl. Phys. Letts., 89, 173503 (2006). H. Lee and Y. Kuo, Electrochem. Solid-State Letts., 9, J21-J23 (2006).
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Magnussen, Olaf M. "(Invited) Atomic-Scale Aspects of Nucleation and Growth at Liquid-Liquid Interfaces." ECS Meeting Abstracts MA2022-01, no. 23 (July 7, 2022): 1152. http://dx.doi.org/10.1149/ma2022-01231152mtgabs.
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Interfaces between liquid metals and liquid electrolytes, in particular the liquid Hg - electrolyte interface, have played a key role in the development of the theory of the electrical double layer and electrochemical adsorption. More recently, liquid-liquid interfaces have regained interest in the field of material synthesis. Unlike solid interfaces, where strain and stress, heterogeneities, and defects strongly influence growth processes, fluid systems provide soft, defect- and stress-free interfaces. In addition, the growth process profits from the high mobility of atoms, molecules, and particles in both liquids, which allows growth from both sides of the phase boundary. A large variety of metallic and non-metallic nanomaterials has been prepared via electrochemical and electroless deposition at such liquid-liquid interfaces. As demonstrated by Maldonado and coworkers, electrodeposition at liquid metal electrodes even allows the growth of nanostructured crystalline semiconductors via a simple one-step, room-temperature electrochemical process [1]. Understanding of the fundamental processes in nucleation and growth at liquid-liquid interfaces is hampered by difficulties in studying these interfaces experimentally on the atomic scale. Most surface-sensitive techniques, especially also scanning probe microscopy methods, cannot access these fluidic phase boundaries. For this reason, the majority of studies relies on electrochemical measurements, optical microscopy, and ex situ investigation of the deposit and thus provide little insight on the initial steps of the growth process. We have shown in the past that hard X-ray scattering methods, such as X-ray reflectivity (XRR) and grazing incidence X-ray scattering (GIXS), are unique tools for determining the atomic liquid-liquid interface structure. In this talk, we present case studies of electrochemically induced growth at liquid interfaces from the first monolayer up to several ten nanometer thick films. The first part discusses the growth of ionic compounds, using lead halides on Hg electrodes as an example. In PbBr2 containing NaF we observed previously growth of a PbBrF layer by operando X-ray scattering. This growth exhibited a complex nucleation and growth behavior, involving a crystalline precursor layer prior to 3D crystal growth [2]. The well-defined subnanometer thick precursor layer provided a template for the subsequent quasi-epitaxial growth of oriented 3D crystallites. Detailed studies on the potential-dependent nucleation and growth kinetics revealed with increasing overpotential a crossover from a low surface density film of large crystals to a compact PbBrF deposit with a saturation thickness of 25 nm [3,4]. In addition, growth on the liquid substrate was found to involve micromechanical effects, such as crystal reorientation and film breakup during dissolution. More recently, we extended these studies to growth in solutions containing only one type of halide anion (Br, Cl, or F). Also here, the formation of precursor layers was observed, indicating that this growth behavior is a general phenomenon. In the second part, joint X-ray scattering studies with Maldonado and coworkers on the electrochemical liquid-liquid-solid deposition of semiconductors from aqueous electrolyte are presented, focusing on Ge electrodeposition on Hg and HgxIn1-x alloy electrodes [5]. We provide evidence for the adsorption of GeO3 - anions on the liquid metal surface and the formation of a crystalline GeO2 adlayer at the positive end of the double layer region. Ge electrodeposition results in nanocrystals, which are separated from the Hg electrode by a water cushion. Furthermore, pronounced Hg surface segregation is found in HgxIn1-x, which protects the electrode surface from oxidation in the potential regime of Ge deposition. [1] Carim, A. I., Collins, S. M., Foley, J. M. & Maldonado, J. Am. Chem. Soc. 133, 13292 (2011) [2] A. Elsen, S. Festersen, B. Runge, C.T. Koops, B. M. Ocko, M. Deutsch, O. Seeck, B. M. Murphy, O. M. Magnussen, Proc. Nat. Acad. Sci., 110, 6663 (2013) [3] B.M. Murphy, S. Festersen, O.M. Magnussen, Nanoscale, 8, 13859 (2016) [4] S. Festersen, B. Runge, C. Koops, F. Bertram, B.M. Ocko, M. Deutsch, B.M. Murphy, O.M. Magnussen, Langmuir, 36, 10905 (2020) [5] D. Pattadar, Q. Cheek, A. Satori, Y. Zhao, P.R. Giri, B. Murphy, O.M. Magnussen, S. Maldonado, Cryst. Growth Des., 21, 1645 (2021)
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Zhang, Shubin, Maksym Zhukovskyi, Boldizsár Jankó, and Masaru Kuno. "Progress in laser cooling semiconductor nanocrystals and nanostructures." NPG Asia Materials 11, no. 1 (October 11, 2019). http://dx.doi.org/10.1038/s41427-019-0156-4.
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Abstract Over the past two decades, there have been sizable efforts to realize condensed phase optical cooling. To date, however, there have been no verifiable demonstrations of semiconductor-based laser cooling. Recently, advances in the synthesis of semiconductor nanostructures have led to the availability of high-quality semiconductor nanocrystals, which possess superior optical properties relative to their bulk counterparts. In this review, we describe how these nanostructures can be used to demonstrate condensed phase laser cooling. We begin with a description of charge carrier dynamics in semiconductor nanocrystals and nanostructures under both above gap and below-gap excitation. Two critical parameters for realizing laser cooling are identified: emission quantum yield and upconversion efficiency. We report the literature values of these two parameters for different nanocrystal/nanostructure systems as well as the measurement approaches used to estimate them. We identify CsPbBr3 nanocrystals as a potential system by which to demonstrate verifiable laser cooling given their ease of synthesis, near-unity emission quantum yields and sizable upconversion efficiencies. Feasibility is further demonstrated through numerical simulations of CsPbBr3 nanocrystals embedded in an aerogel matrix. Our survey generally reveals that optimized semiconductor nanocrystals and nanostructures are poised to demonstrate condensed phase laser cooling in the near future.
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Dalui, Amit, Katsuhiko Ariga, and Somobrata Acharya. "Colloidal Semiconductor Nanocrystals: From Bottom-up Nanoarchitectonics to Energy Harvesting Applications." Chemical Communications, 2023. http://dx.doi.org/10.1039/d3cc02605a.
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Colloidal semiconductor nanocrystals (NCs) have been extensively investigated owing to their unique properties induced by the quantum confinement effect. The advent of colloidal synthesis routes led to the design of...