Journal articles: 'Optoelectronics - NCs'

1

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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Yang, Liuli, Ting Wang, Qiuhong Min, Chaojie Pi, Fan Li, Xiao Yang, Kongzhai Li, et al. "Ultrahigh photo-stable all-inorganic perovskite nanocrystals and their robust random lasing." Nanoscale Advances 2, no. 2 (2020): 888–95. http://dx.doi.org/10.1039/c9na00775j.

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Pinto, S. R. C., P. Caldelas, A. G. Rolo, A. Chahboun, and M. J. M. Gomes. "Estimation of Ge nanocrystals size by Raman, X-rays, and HRTEM techniques." Microscopy and Microanalysis 14, S3 (September 2008): 61–64. http://dx.doi.org/10.1017/s1431927608089393.

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Ge NCs have attracted considerable attention because of their potential applications in nonvolatile memory and integrated optoelectronics. A number of groups have already proposed integrate flash memories based on Ge NCs embedded SiO2 matrix. Since Al2O3 presents a high dielectric constant comparatively to SiO2, it is a good candidate to replace silica in flash memory systems, and therefore improve their performances. Moreover, Al2O3 presents good mechanical properties, and supports high temperature, which leads it to be an ideal material for Si processing conditions. However, a few studies have been reported on Ge NCs embedded in Al2O3 matrix.

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Ghoshal, Sib Krishna, M. R. Sahar, R. Arifin, M. S. Rohani, and K. Hamzah. "Surface States and Band Gap Correlation in Silicon Nanoclusters." Advanced Materials Research 1107 (June 2015): 308–13. http://dx.doi.org/10.4028/www.scientific.net/amr.1107.308.

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Tuning the visible emission of Si nanomaterials by modifying their size and shape is one of the key issue in optoelectronics. The observed optical gain in Si-nanoclusters (NCs) has given further impulse to nanosilicon research. We develop a phenomenological model by combining the effects of surface passivation, exciton states and quantum confinement (QC). The size and passivation dependent band gap, oscillator strength, radiative lifetime and photoluminescence (PL) intensity for NCs with diameter ranging from 1.0 to 6.0 nm are presented. By controlling a set of fitting parameters, it is possible to tune the optical band gap, PL peak and intensity. In case of pure clusters, the band gap is found to decrease with increasing NC size. Furthermore, the band gap increases on passivating the surface of the cluster with hydrogen and oxygen respectively in which the effect of oxygen is more robust. Both QC and surface passivation in addition to exciton effects determine the optical and electronic properties of silicon NCs. Visible luminescence is due to radiative recombination of electrons and holes in the quantum-confined NCs. The role of surface states on the band gap as well as on the HOMO-LUMO states is also examined and a correlation is established. Our results are in conformity with other observations. The model can be extended to study the light emission from other nanostructures and may contribute towards the development of Si based optoelectronics.

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Patnaik, Sumanta Kumar, Sukanta Kumar Triapthy, and Surendra Nath Sahu. "Synthesis and characterization of small size fluorescent LEEH caped blue emission ZnTe quantum dots." Materials Science-Poland 35, no. 1 (April 23, 2017): 1–5. http://dx.doi.org/10.1515/msp-2017-0012.

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AbstractWe report here for the first time the synthesis of LEEH caped very small size (2 nm) ZnTe quantum dots at low temperature (less than 100 °C) using a simple chemical route. The effects of aging and stirring time on the absorption spectra of the quantum dots were investigated. The synthesized nanocrystal (NC) was characterized by PL, TEM, XRD and the formation of very small size quantum dots having FCC structure was confirmed. Further, blue emission from the prepared sample was observed during exposure to monochromatic UV radiation. ZnTe NCs obtained in this study were found to be more stable compared to those presented in literature reports. ZnTe NCs may be considered as a new material in place of CdTe for optoelectronics devices.

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Liu, Albert, Diogo B. Almeida, Luiz G. Bonato, Gabriel Nagamine, Luiz F. Zagonel, Ana F. Nogueira, Lazaro A. Padilha, and S. T. Cundiff. "Multidimensional coherent spectroscopy reveals triplet state coherences in cesium lead-halide perovskite nanocrystals." Science Advances 7, no. 1 (January 2021): eabb3594. http://dx.doi.org/10.1126/sciadv.abb3594.

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Advances in optoelectronics require materials with novel and engineered characteristics. A class of materials that has garnered tremendous interest is metal-halide perovskites, stimulated by meteoric increases in photovoltaic efficiencies of perovskite solar cells. In addition, recent advances have applied perovskite nanocrystals (NCs) in light-emitting devices. It was found recently that, for cesium lead-halide perovskite NCs, their unusually efficient light emission may be due to a unique excitonic fine structure composed of three bright triplet states that minimally interact with a proximal dark singlet state. To study this fine structure without isolating single NCs, we use multidimensional coherent spectroscopy at cryogenic temperatures to reveal coherences involving triplet states of a CsPbI3 NC ensemble. Picosecond time scale dephasing times are measured for both triplet and inter-triplet coherences, from which we infer a unique exciton fine structure level ordering composed of a dark state energetically positioned within the bright triplet manifold.

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Wang, Yen Po, Hsin Chieh Li, Yan Chi Huang, and Chih Shan Tan. "Synthesis and Applications of Halide Perovskite Nanocrystals in Optoelectronics." Inorganics 11, no. 1 (January 11, 2023): 39. http://dx.doi.org/10.3390/inorganics11010039.

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The perovskites used for optoelectronic devices have been more attractive during recent years due to their wide variety of advantages, such as their low cost, high photoluminescence quantum yield (PLQY), high carrier mobility, flexible bandgap tunability, and high light absorption ability. However, optoelectronic applications for traditional inorganic and organic materials present dilemmas due to their hardly tunable bandgap and instability. On the other hand, there are some more important benefits for perovskite nanocrystals, such as a size-dependent bandgap and the availability of anion exchange at room temperature. Therefore, perovskite NC-based applications are currently favored, offering a research direction beyond perovskite, and much research has focused on the stability issue and device performance. Thus, the synthesis and applications of perovskite NCs need to be thoroughly discussed for the future development of solar cells, light-emitting diodes, photodetectors, and laser research.

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Arumugam, Gowri Manohari, Santhosh Kumar Karunakaran, Raquel E. Galian, and Julia Pérez-Prieto. "Recent Progress in Lanthanide-Doped Inorganic Perovskite Nanocrystals and Nanoheterostructures: A Future Vision of Bioimaging." Nanomaterials 12, no. 13 (June 21, 2022): 2130. http://dx.doi.org/10.3390/nano12132130.

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All-inorganic lead halide perovskite nanocrystals have great potential in optoelectronics and photovoltaics. However, their biological applications have not been explored much owing to their poor stability and shallow penetration depth of ultraviolet (UV) excitation light into tissues. Interestingly, the combination of all-inorganic halide perovskite nanocrystals (IHP NCs) with nanoparticles consisting of lanthanide-doped matrix (Ln NPs, such as NaYF4:Yb,Er NPs) is stable, near-infrared (NIR) excitable and emission tuneable (up-shifting emission), all of them desirable properties for biological applications. In addition, luminescence in inorganic perovskite nanomaterials has recently been sensitized via lanthanide doping. In this review, we discuss the progress of various Ln-doped all-inorganic halide perovskites (LnIHP). The unique properties of nanoheterostructures based on the interaction between IHP NCs and Ln NPs as well as those of LnIHP NCs are also detailed. Moreover, a systematic discussion of basic principles and mechanisms as well as of the recent advancements in bio-imaging based on these materials are presented. Finally, the challenges and future perspectives of bio-imaging based on NIR-triggered sensitized luminescence of IHP NCs are discussed.

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Sadighian, James C., Michael L. Crawford, and Cathy Y. Wong. "Rapid sampling during synthesis of lead halide perovskite nanocrystals for spectroscopic measurement." MRS Advances 4, no. 36 (2019): 1957–64. http://dx.doi.org/10.1557/adv.2019.263.

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ABSTRACTThe photophysical properties of lead halide perovskite nanocrystals (NCs) are critical to their potential application in light emitting devices and other optoelectronics, and are typically characterized using optical spectroscopies. Measurements of nuclei and nascent NC photophysics during synthesis provide insight into how the reaction can be changed to control the properties of the resulting NCs. However, these measurements are typically only performed ex situ after growth is halted by centrifuging the reaction mixture for several minutes. Here, a method is reported to rapidly sample the reaction mixture during a solvation-limited synthesis to enable multiple spectroscopic measurements during nucleation and NC growth. Absorbance and fluorescence measurements of a reaction mixture during the formation of methylammonium lead triiodide perovskite NCs are reported. The changing positions of spectral features as a function of reaction time show the expected weakening of exciton confinement during NC growth. The evolving fluorescence spectra demonstrate that the capping and surface passivation of nascent NCs changes during the reaction. The species in the reaction mixture, particularly during the early stages of the synthesis, are shown to be unstable. This indicates that, even for a relatively slow solvation-limited reaction, the photophysics of the reaction mixture can only be accurately captured if spectroscopic measurements are completed within seconds of sampling. The common use of centrifugation to quench NC syntheses prior to spectroscopic measurement biases the NC population towards more stable, well-capped NCs and does not accurately report on the full NC population in a reaction mixture.

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Żaba, Adam, Svitlana Sovinska, Tetiana Kirish, Adam Węgrzynowicz, and Katarzyna Matras-Postołek. "Photodegradation Process of Organic Dyes in the Presence of a Manganese-Doped Zinc Sulfide Nanowire Photocatalyst." Materials 14, no. 19 (October 6, 2021): 5840. http://dx.doi.org/10.3390/ma14195840.

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Zinc sulfide (ZnS) nanowires represent a promising candidate in many fields, including optoelectronics and photocatalysis because of their advantages such as excellent optical properties, chemical stability and an easy-scalable simple synthesis method. In this study, an energy-friendly microwave radiation process was used to develop the single-step, solvothermal process for the growth of manganese-doped zinc sulfide (ZnS) and undoped nanocrystals (NCs) in the forms of nanowires using two short amines as a stabilizer, e.g. ethylenediamine and hydrazine, respectively. ZnS nanowires doped with Mn atoms show absorbance in UV and in the visible region of the spectrum. The photocatalytic degradation of rhodamine B in the presence of Mn-doped and undoped ZnS nanocrystals illuminated with only a 6-W UV lamp has been comprehensively studied. The effect of Mn doping and the presence of a nanocrystal stabilizer on the degradation process was determined. It was found that the efficiency of a photocatalytic degradation process was strongly affected by both factors: the doping process of nanowires with Mn2+ atoms and the attachment of ligands to the nanocrystal surface.

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Zhu, Yiyue, Wen Huang, Yifei He, Lei Yin, Yiqiang Zhang, Deren Yang, and Xiaodong Pi. "Perovskite-Enhanced Silicon-Nanocrystal Optoelectronic Synaptic Devices for the Simulation of Biased and Correlated Random-Walk Learning." Research 2020 (September 2, 2020): 1–9. http://dx.doi.org/10.34133/2020/7538450.

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Silicon- (Si-) based optoelectronic synaptic devices mimicking biological synaptic functionalities may be critical to the development of large-scale integrated optoelectronic artificial neural networks. As a type of important Si materials, Si nanocrystals (NCs) have been successfully employed to fabricate optoelectronic synaptic devices. In this work, organometal halide perovskite with excellent optical asborption is employed to improve the performance of optically stimulated Si-NC-based optoelectronic synaptic devices. The improvement is evidenced by the increased optical sensitivity and decreased electrical energy consumption of the devices. It is found that the current simulation of biological synaptic plasticity is essentially enabled by photogating, which is based on the heterojuction between Si NCs and organometal halide perovskite. By using the synaptic plasticity, we have simulated the well-known biased and correlated random-walk (BCRW) learning.

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Zhang, Fei, Zhuangzhuang Ma, Zhifeng Shi, Xu Chen, Di Wu, Xinjian Li, and Chongxin Shan. "Recent Advances and Opportunities of Lead-Free Perovskite Nanocrystal for Optoelectronic Application." Energy Material Advances 2021 (February 5, 2021): 1–38. http://dx.doi.org/10.34133/2021/5198145.

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Metal halide perovskite nanocrystals (NCs), as a new class of light-emitting and light-harvesting materials, have recently attracted intensive attention for an impressive variety of optoelectronic applications. However, the lead toxicity and poor stability of such materials severely restrict their practical applications and future commercialization. Lead-free perovskite NCs and their derivatives, designed by the reasonable chemical substitution of Pb with other nontoxic elements, are recently booming as an attractive alternative to lead-based counterparts. In this review, we firstly present a comprehensive overview of currently explored lead-free perovskite NCs with an emphasis on their design routes, morphologies, optoelectronic properties, and environmental stability issues. Then, we discuss the preliminary achievements of lead-free perovskite NCs in versatile optoelectronic applications, such as light-emitting devices, solar cells, photodetectors, and photocatalysis. We finish this review with a critical outlook into the currently existing challenges and possible development opportunities of this rapidly evolving field.

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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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Park, Jusun, and Ju Young Woo. "Thermally Stable All Inorganic Cesium Lead Halide Perovskite Nanocrystals." Journal of Flexible and Printed Electronics 1, no. 1 (August 2022): 91–99. http://dx.doi.org/10.56767/jfpe.2022.1.1.91.

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All inorganic CsPbX3 (X is Cl, Br, or I) perovskite nanocrystals (CPX NCs) have become one of the most promising materials which can be integrated into high performance optoelectronic devices such as light emitting diodes, sensors, and solar cells. However, poor thermal stability seriously hampers successful demonstration of commercially available optoelectronic devices based on CPX NCs. In this study, we demonstrate strikingly enhanced thermal stability of CPX NCs by employing impurity metal halides during synthesis. Thermal stability of CPX NCs were investigated by microscopic and spectroscopic characterizations, and it turned out that various metal halides are effective for enhancement of thermal stability of CPX NCs. CPX NCs maintains their original structures and properties with little sign of instability such as merging and phase transformations when the NCs were synthesized by adding impurity metal halides. We finally propose plausible mechanisms on enhanced thermal stability of CPB NCs synthesized under the presence of impurity metal halides.

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Hu, Yue, Yuxin Zhang, Chaoqun Yang, Ji Li, and Li Wang. "The cation–anion co-exchange in CsPb1−xFex(Br1−yCly)3 nanocrystals prepared using a hot injection method." RSC Advances 10, no. 55 (2020): 33080–85. http://dx.doi.org/10.1039/d0ra06238c.

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Ding, Hongwei, Weiwei Liu, Youkun Zheng, Chunmei Li, Hui Jiang, and Xuemei Wang. "Transition metal halide-doped, highly stable all-inorganic perovskite nanocrystals for fabrication of white light-emitting diodes." Journal of Materials Chemistry C 7, no. 6 (2019): 1690–95. http://dx.doi.org/10.1039/c8tc05732j.

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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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Wang, Yujie, Utkarsh Ramesh, Charles K. A. Nyamekye, Bradley J. Ryan, Rainie D. Nelson, Abdulla M. Alebri, Umar H. Hamdeh, Atefe Hadi, Emily A. Smith, and Matthew G. Panthani. "Synthesis of germanium nanocrystals from solid-state disproportionation of a chloride-derived germania glass." Chemical Communications 55, no. 43 (2019): 6102–5. http://dx.doi.org/10.1039/c9cc01676g.

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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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Vishaka, Halali V., George K. Jesna, Pasha Altaf, K. Sarina, and Balakrishna R. Geetha. "Lattice constriction and trapped excitons: a structure–property relationship unveiled in CsPbBr3 perovskite QDs." Journal of Materials Chemistry C 8, no. 47 (2020): 17090–98. http://dx.doi.org/10.1039/d0tc04120c.

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Haydous, Fatima, James M. Gardner, and Ute B. Cappel. "The impact of ligands on the synthesis and application of metal halide perovskite nanocrystals." Journal of Materials Chemistry A 9, no. 41 (2021): 23419–43. http://dx.doi.org/10.1039/d1ta05242j.

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Shao, Guangzhan, Yi Zhao, Yanxia Yu, Haisheng Yang, Xiaodong Liu, Yujie Zhang, Weidong Xiang, and Xiaojuan Liang. "Bright emission and high photoluminescence CsPb2Br5 NCs encapsulated in mesoporous silica with ultrahigh stability and excellent optical properties for white light-emitting diodes." Journal of Materials Chemistry C 7, no. 43 (2019): 13585–93. http://dx.doi.org/10.1039/c9tc04442f.

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Lee, Hyeonjun, Da-Eun Yoon, Sungjun Koh, Moon Sung Kang, Jaehoon Lim, and Doh C. Lee. "Ligands as a universal molecular toolkit in synthesis and assembly of semiconductor nanocrystals." Chemical Science 11, no. 9 (2020): 2318–29. http://dx.doi.org/10.1039/c9sc05200c.

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Liu, Ying, Maxim S. Molokeev, and Zhiguo Xia. "Lattice Doping of Lanthanide Ions in Cs2AgInCl6 Nanocrystals Enabling Tunable Photoluminescence." Energy Material Advances 2021 (February 24, 2021): 1–9. http://dx.doi.org/10.34133/2021/2585274.

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Lead-free halide double perovskite Cs2AgInCl6 has become the research hotspot in the optoelectronic fields. It is a challenge to utilize the lattice doping by different lanthanide ions with rich and unique photoluminescence (PL) emissions for emerging photonic applications. Here, we successfully incorporated Dy3+, Sm3+, and Tb3+ ions into Cs2AgInCl6 nanocrystals (NCs) by the hot-injection method, bringing diverse PL emissions of yellowish, orange, and green light in Cs2AgInCl6:Ln3+ (Ln3+ = Dy3+, Sm3+, Tb3+). Moreover, benefiting from the energy transfer process, Sm3+ and Tb3+ ion-codoped Cs2AgInCl6 NCs achieved tunable emission from green to yellow orange and a fluorescent pattern from the as-prepared NC-hexane inks by spray coating was made to show its potential application in fluorescent signs and anticounterfeiting technology. This work indicates that lanthanide ions could endow Cs2AgInCl6 NCs the unique and tunable PL properties and stimulate the development of lead-free halide perovskite materials for new optoelectronic applications.

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Mastria, R., and A. Rizzo. "Mastering heterostructured colloidal nanocrystal properties for light-emitting diodes and solar cells." Journal of Materials Chemistry C 4, no. 27 (2016): 6430–46. http://dx.doi.org/10.1039/c6tc01334a.

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The advent of surfactant-assisted synthesis of thermodynamically stable colloidalsolutions of NCs has led to the possibility of building heterostructured NCs (HNCs) comprising two or more different materials joined together. By tailoring the composition, shape and size of each component, HNCs with gradually higher levels of complexity have been realized, endowing them with outstanding characteristics and optoelectronic properties.

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Kim, Sung, Dong Hee Shin, Dong Yeol Shin, Chang Oh Kim, Jae Hee Park, Seung Bum Yang, Suk-Ho Choi, Seung Jo Yoo, and Jin-Gyu Kim. "Luminescence Properties of Si Nanocrystals Fabricated by Ion Beam Sputtering and Annealing." Journal of Nanomaterials 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/572746.

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During the past several decades, Si nanocrystals (NCs) have received remarkable attention in view of potential optoelectronic device applications. This paper summarizes recent progress in the study of luminescence from Si NCs, such as photoluminescence (PL), cathodoluminescence, time-solved PL, and electroluminescence. The paper is especially focused on Si NCs produced by ion beam sputtering deposition ofSiOxsingle layer orSiOx/SiO2multilayers and subsequent annealing. The effects of stoichiometry (x) and thickness of SiOxlayers on the luminescence are analyzed in detail and discussed based on possible mechanisms.

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Pi, Xiaodong. "(Invited, Digital Presentation) Exploring New Applications of Luminescent Silicon Nanocrystals." ECS Meeting Abstracts MA2022-01, no. 20 (July 7, 2022): 1078. http://dx.doi.org/10.1149/ma2022-01201078mtgabs.

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The luminescence of silicon nanocrystals (Si NCs) has been traditionally studied for various applications such as light-emitting diodes, solar cells and bioimaging[1]. In the past few years we have started exploring the use of Si NCs for emerging optoelectronic synaptic devices[2,3]. As an important type of optoelectronic synaptic devices, electroluminescent synaptic devices have been fabricated by using Si NCs[4,5]. Under the stimulation of electrical spikes these devices give out electroluminescence that decays in the timeframe of tens of microseconds, enabling a series of synaptic functionalities and logic functions. In addition, we have synthesized Er-hyperdoped Si NCs, which emit light simultaneously at the wavelengths of 830 and 1540 nm. It is found that Er-hyperdoped Si NCs are a powerful ratiometric near-infrared fluorescent platform. The rationmetric near-infrared fluorescence may be well used for temperature sensing, which further enables the construction of logic gates[6]. [1] Z. Y. Ni, et al., Materials Science & Engineering R 138, 85-117 (2019). [2] L. Yin, et al., Nano Letters 20, 5, 3378–3387 (2020). [3] Y. Wang, et al., Advanced Functional Materials 2107973 (2021). [4] S. Y. Zhao, et al., Nano Energy 54, 383-389 (2018) [5] S. Y. Zhao, et al., Science China Materials 62, 1470-1478 (2019) [6] K. Wang, et al., to be submitted.

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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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Dayan, Osman, Arife Gencer Imer, Melek Tercan, Aysegul Dere, Abdullah G. Al-Sehemi, Ahmed A. Al-Ghamdi, and Fahrettin Yakuphanoglu. "Dye sensitized solar cell-based optoelectronic device using novel [Ru(L1)(L2)(NCS)2] complex." Journal of Molecular Structure 1238 (August 2021): 130464. http://dx.doi.org/10.1016/j.molstruc.2021.130464.

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Tan, Xiaohong, Xiaoqing Yao, and Zhishun Chen. "Synthesis and Application of Lead Halide Perovskite Nanocrystals@Metal-Organic Frameworks Composites." Journal of Physics: Conference Series 2393, no. 1 (December 1, 2022): 012010. http://dx.doi.org/10.1088/1742-6596/2393/1/012010.

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Abstract LHP@MOFs composites, combined lead halide perovskite (LHP) nanocrystals (NCs) with metal-organic frameworks (MOFs), show great potential in the field of optoelectronic applications. Meanwhile, the stability of LHP NCs is improved by encapsulating them in MOFs. The recent progress of LHP@MOFs composites in terms of synthesis and applications is first summarized in this paper. Thereafter, a brief outlook is given for the possible future prospects of LHP@MOFs composites, which may provide the further development of stable LHP@MOFs.

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Timmerman, Dolf, Ying Ying Tang, Peter Schall, and Yasufumi Fujiwara. "(Invited, Digital Presentation) Ultrafast Spectroscopy of Inorganic Perovskite Nanocrystals and Their Assemblies: Uncovering the Multiple Exciton Generation Rate and Band-Formation." ECS Meeting Abstracts MA2022-02, no. 20 (October 9, 2022): 913. http://dx.doi.org/10.1149/ma2022-0220913mtgabs.

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Inorganic perovskite nanocrystals (NCs) display attractive structural and optical properties, and have perspective in a wide range of optoelectronic applications. One interesting feature is their relatively slow hot carrier cooling rate, which allows to follow carrier dynamics in great detail with ultrafast spectroscopic techniques. In this talk, we present studies of the ultrafast carrier dynamics of perovskite NCs and assembled structures. Typically, when the excitation photon energy is increased, and thus the excess energy of the created carriers, the cooling time of the carriers towards the bandedge increases along. However, for CsPbI3 NCs, when the photon energy exceeds a certain threshold energy the cooling time starts to decrease, indicating that a competing relaxation pathway opens up which funnels carriers towards the bandedge. This threshold energy indicates the onset of a carrier multiplication process, in which absorption of a single photon leads to the creation of multiple electron-hole pairs. This process can also be inferred by following the carrier concentration, which shows a delayed build-up following the excitation pulse. The carrier dynamics in this system can be modeled within a framework of two competing cooling mechanisms. With the experimentally determined carrier cooling rate and threshold energy it is possible to extract the time-constant associated with the carrier multiplication process. Experiments on highly ordered CsPbBr3 NCs, so-called supercrystals, revealed how the photophysics are altered due to the inter-NC coupling as compared to the individual NCs. Next to a red-shift of the absorption and photoluminescence peak, the supercrystals show signatures of band-like states. The observation of a reduced Stokes-shift, decreased biexciton binding energy and increased carrier cooling rates, support the formation of delocalized states resulting from the coupling between individual NCs. These results open perspectives for assembled NCs for application in optoelectronic devices, with design opportunities exceeding the level of nanocrystal and bulk material.

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Wang, Chao, Lucheng Peng, Xiaotian Yang, Renguo Xie, and Shouhua Feng. "Cd–Cu–Fe–S quaternary nanocrystals exhibiting excellent optical/optoelectronic properties." Nanoscale 11, no. 14 (2019): 6533–37. http://dx.doi.org/10.1039/c8nr10507c.

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Liao, Lianxing, Kunhua Quan, Xiangshi Bin, Ruosheng Zeng, and Tao Lin. "Bandgap and Carrier Dynamic Controls in CsPbBr3 Nanocrystals Encapsulated in Polydimethylsiloxane." Crystals 11, no. 9 (September 17, 2021): 1132. http://dx.doi.org/10.3390/cryst11091132.

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Bandgap tunability through ion substitution is a key feature of lead halide perovskite nanocrystals (LHP-NCs). However, the low stability and low luminescent performance of CsPbCl3 hinder their full-color applications. In this work, quantum confinement effect (QCE) was utilized to control the bandgap of CsPbBr3 NCs instead of using unstable CsPbCl3, which possess much higher emission efficiency in blue spectra region. Studies of microstructures, optical spectra and carrier dynamics revealed that tuning the reaction temperature was an effective way of controlling the NC sizes as well as QCE. Furthermore, the obtained CsPbBr3 NCs were encapsulated in a PDMS matrix while maintaining their size distribution and quantum-confined optoelectronic properties. The encapsulated samples showed long-term air and water stability. These results provide valuable guidance for both applications of LHP-NCs and principal investigation related to the carrier transition in LHP-NCs.

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Coyopol, A., G. García-Salgado, T. Díaz-Becerril, H. Juárez, E. Rosendo, R. López, M. Pacio, J. A. Luna-López, and J. Carrillo-López. "Optical and Structural Properties of Silicon Nanocrystals Embedded in SiOxMatrix Obtained by HWCVD." Journal of Nanomaterials 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/368268.

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The interest in developing optoelectronic devices integrated in the same silicon chip has motivated the study of Silicon nanocrystals (Si-ncs) embedded in SiOx(nonstoichiometric silicon oxides) films. In this work, Si-ncs in SiOxfilms were obtained by Hot Wire Chemical Vapor Deposition (HWCVD) at 800, 900, and 1000°C. The vibration modes of SiOxfilms were determined by FTIR measurements. Additionally, FTIR and EDAX were related to get the proper composition of the films. Micro-Raman studies in the microstructure of SiOxfilms reveal a transition from amorphous-to-nanocrystalline phase when the growth temperature increases; thus, Si-ncs are detected. Photoluminescence (PL) measurement shows a broad emission from 400 to 1100 nm. This emission was related with both Si-ncs and interfacial defects present in SiOxfilms. The existence of Si-ncs between 3 and 6 nm was confirmed by HRTEM.

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Le, Anh Thi, Minh Tan Man, and Minh Hoa Nguyen. "Effect of shell thickness on heterostructure of CdSe/CdS core/shell nanocrystals." Hue University Journal of Science: Natural Science 131, no. 1B (June 30, 2022): 5–10. http://dx.doi.org/10.26459/hueunijns.v131i1b.6491.

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Core/shell hetero-nanostructures are promising materials for fabricating optoelectronic devices, photodetectors, bioimaging, and biosensing. The CdSe/CdS core/shell nanocrystals (NCs) were synthesized in a wet chemical reaction. The shell thickness was modified by varying reaction times. The structure and optical properties as a function of the CdS shell thickness were investigated. A systematic redshift of the first exciton absorption peaks and photoluminescent (PL) spectra occurred after coating with CdS confirmed the shell growth over the CdSe core. The PL's intensity increased compared with that of bare NCs. The formation of high-quality NCs with uniform size distribution was shown in the transmission electron microscopy (TEM) image and confirmed by the narrow PL band and small FWHM.

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Linehan, Keith, Darragh Carolan, Daithi Ó. Sé, and Hugh Doyle. "Synthesis and Compositional Control of Size Monodisperse SixGe1-x Nanocrystals for Optoelectronic Applications." MRS Proceedings 1551 (2013): 11–16. http://dx.doi.org/10.1557/opl.2013.1042.

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ABSTRACTAlkyl-terminated SixG1-x nanocrystals are prepared at room temperature by co-reduction of Si and Ge precursors by hydride reducing agents within inverse micelles. Compositional control of the alloy silicon-germanium NCs (ca. 3.6 nm) is achieved by varying the relative amounts of each precursor used in the synthesis. Transmission electron microscopy imaging confirmed that the NCs are highly crystalline with a narrow size distribution; optical spectroscopy shows strong quantum confinement effects, with moderate absorption in the UV spectral range, and a strong blue emission with a marked dependency on excitation wavelength.

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Wu, Ruixiang, Xiaoshuai Wang, Jingjing Luo, Xin Liu, Fengjie Guo, Bin Li, Shengzhi Wang, Peigeng Han, and Xiangyang Miao. "Photon-Energy-Dependent Reversible Charge Transfer Dynamics of Double Perovskite Nanocrystal-Polymer Nanocomposites." Nanomaterials 12, no. 23 (December 4, 2022): 4300. http://dx.doi.org/10.3390/nano12234300.

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Combining steady-state photoluminescence and transient absorption (TA) spectroscopy, we have investigated the photoinduced charge transfer dynamics between lead-free Mn-doped Cs2NaIn0.75Bi0.25Cl6 double perovskite (DP) nanocrystals (NCs) and conjugated poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). Upon ultraviolet-A excitation, the photoinduced absorption feature of DP NCs/MDMO-PPV nanocomposites disappeared, and the stimulated emission weakened in the TA spectrum. This was due to charge transfer from the MDMO-PPV polymers to DP NCs. Upon a higher photon-energy ultraviolet-C excitation, stimulated emission and photoinduced absorption features vanished, indicating there existed a reversible charge transfer from DP NCs to MDMO-PPV polymers. Reversible charge transfer of Mn-doped DP NCs/MDMO-PPV nanocomposites was tuned by varying the excitation photon-energy. The manipulation of reversible charge transfer dynamics in the perovskite-polymer nanocomposites opens a new avenue for optical and optoelectronic applications.

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Shen, Wei, Jianbin Zhang, Ruimin Dong, Yanfeng Chen, Liu Yang, Shuo Chen, Zhan Su, et al. "Stable and Efficient Red Perovskite Light-Emitting Diodes Based on Ca²⁺-Doped CsPbI₃ Nanocrystals." Research 2021 (December 6, 2021): 1–11. http://dx.doi.org/10.34133/2021/9829374.

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α-CsPbI3 nanocrystals (NCs) with poor stability prevent their wide applications in optoelectronic fields. Ca2+ (1.00 Å) as a new B-site doping ion can successfully boost CsPbI3 NC performance with both improved phase stability and optoelectronic properties. With a Ca2+/Pb2+ ratio of 0.40%, both phase and photoluminescence (PL) stability could be greatly enhanced. Facilitated by increased tolerance factor, the cubic phase of its solid film could be maintained after 58 days in ambient condition or 4 h accelerated aging process at 120°C. The PL stability of its solution could be preserved to 83% after 147 days in ambient condition. Even using UV light to accelerate aging, the T50 of PL could boost 1.8-folds as compared to CsPbI3 NCs. Because Ca2+ doping can dramatically decrease defect densities of films and reduce hole injection barriers, the red light-emitting diodes (LEDs) exhibited about triple enhancement for maximum the external quantum efficiency (EQE) up to 7.8% and 2.2 times enhancement for half-lifetime of LED up to 85 min. We believe it is promising to further explore high-quality CsPbI3 NC LEDs via a Ca2+-doping strategy.

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Zhou, Jigang, Jun Zhu, Jack Brzezinski, and Zhifeng Ding. "Tunable electrogenerated chemiluminescence from CdSe nanocrystals." Canadian Journal of Chemistry 87, no. 1 (January 1, 2009): 386–91. http://dx.doi.org/10.1139/v08-180.

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Electrochemical behavior and related optoelectronic properties of CdSe nanocrystals (NCs) in aprotic solutions have been investigated. NCs of 2.50 ± 0.50 nm diameter were synthesized using a modified procedure in which the temperatures at the time of Se precursor injection and NC growth were controlled. The electrochemical band gap was found to agree with those determined by UV–vis absorption spectroscopy and by the tunneling current-voltage spectrum in the literature. Electrogenerated chemiluminescence of the NCs with peak maxima at 1.90 eV (red, 653 nm) and 2.55 eV (blue, 486 nm) can be generated and altered by scanning the voltage between –1.60 and –1.80 V and between –2.00 and –2.20 V, respectively. The results demonstrate the potential capability of the NCs for light emission tuned by the applied potential.Key words: CdSe nanocrystals, electrochemistry, electrogenerated chemiluminescence, UV–vis spectroscopy, photoluminescence.

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Li, Haixia, Bingyi Liu, Weiwei Lin, Yang Liu, Yu Wang, Zhongyuan Zhang, Lun Xiong, and Jiayou Tao. "Enhancing Performance of Broadband Photodetectors Based on Perovskite CsPbBr₃ Nanocrystals/ZnO-Microwires Heterostructures." Science of Advanced Materials 13, no. 9 (September 1, 2021): 1748–55. http://dx.doi.org/10.1166/sam.2021.4072.

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A broadband photodetector response in the ultraviolet (UV)-to-green range (up to 530 nm) based on perovskite CsPbBr3 nanocrystals (NCs)/ZnO-microwires (MWs) heterostructures was realized via a convenient spin-coating method. Under UV light (365 nm) illumination, compared with a bare-ZnO-MW-based photodetector, the CsPbBr3-NCs/ZnO-MWs-heterostructure-based photodetector exhibited a faster photoresponse (<0.1 s) and higher current responsivity (93.50 AW−1), external quantum efficiency (3399%), and detectivity (4.4 × 1010). In addition, the photodetector based on CsPbBr3-NCs/ZnO-MWs heterostructures also exhibited a very fast photoresponse to green light (530 nm). These can be ascribed to the strong light-trapping ability of CsPbBr3 NCs and high charge-transfer efficiency at the CsPbBr3-NCs/ZnO-MWs-heterojunction interface due to the built-in field, which facilitates the spatial separation of the photogenerated carriers. Therefore, this work will develop perovskite/ZnO nanomaterials as promising building blocks for broadband photodetectors and wider optoelectronic applications.

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Islam, Amjad, Syed Hamad Ullah Shah, Zeeshan Haider, Muhammad Imran, Al Amin, Syed Kamran Haider, and Ming-De Li. "Biological Interfacial Materials for Organic Light-Emitting Diodes." Micromachines 14, no. 6 (May 31, 2023): 1171. http://dx.doi.org/10.3390/mi14061171.

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Organic optoelectronic devices have received appreciable attention due to their low cost, mechanical flexibility, band-gap engineering, lightness, and solution processability over a broad area. Specifically, realizing sustainability in organic optoelectronics, especially in solar cells and light-emitting devices, is a crucial milestone in the evolution of green electronics. Recently, the utilization of biological materials has appeared as an efficient means to alter the interfacial properties, and hence improve the performance, lifetime and stability of organic light-emitting diodes (OLEDs). Biological materials can be known as essential renewable bio-resources obtained from plants, animals and microorganisms. The application of biological interfacial materials (BIMs) in OLEDs is still in its early phase compared to the conventional synthetic interfacial materials; however, their fascinating features (such as their eco-friendly nature, biodegradability, easy modification, sustainability, biocompatibility, versatile structures, proton conductivity and rich functional groups) are compelling researchers around the world to construct innovative devices with enhanced efficiency. In this regard, we provide an extensive review of BIMs and their significance in the evolution of next-generation OLED devices. We highlight the electrical and physical properties of different BIMs, and address how such characteristics have been recently exploited to make efficient OLED devices. Biological materials such as ampicillin, deoxyribonucleic acid (DNA), nucleobases (NBs) and lignin derivatives have demonstrated significant potential as hole/electron transport layers as well as hole/electron blocking layers for OLED devices. Biological materials capable of generating a strong interfacial dipole can be considered as a promising prospect for alternative interlayer materials for OLED applications.

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Yu, Yang, Chengyu Li, Cheng Li, Wei Zhou, Peigeng Han, Kun Zhao, Hui Li, and Ruifeng Lu. "Conversion of the non-luminous lead-free inorganic halide perovskite variant CsNiCl₃ nanocrystals into photoluminescent materials by Cu⁺ and In³⁺ doping." APL Materials 10, no. 11 (November 1, 2022): 111110. http://dx.doi.org/10.1063/5.0123508.

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All-inorganic CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (NCs) as promising optoelectronic materials have attracted tremendous research interest because of their intense photoluminescence, broad absorption, and tunable bandgap. Even with these fascinating characteristics, their practical applications are still suffering from the presence of toxic lead and inadequate stability. Herein, we successfully synthesize CsNiCl3 NCs in a comparatively low-temperature route for the first time. By Cu+ and In3+ doping, CsNiCl3 NCs can be converted from non-luminous into photoluminescent materials. The broad green fluorescence emission at 530 nm of CsNiCl3 NCs with high luminescence intensity and quantum yield (42.2%) is achieved. Broad band emission with a large Stokes shift can be attributed to the recombination process of self-trapped excitons (STEs). The transient fluorescence spectra of the doped CsNiCl3 NCs show two ultra-long lifetimes of about 50 and 120 µs, which are assigned to the STE recombination, indicating that the nonradiative recombination process is suppressed after doping. Our research provides an innovative method for developing environmentally friendly lead-free metal halide NCs.

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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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Xu, Jia, Yatao Pan, Zhongran Wei, Shida Luo, Xia Ran, Yulu He, Renming Liu, Zhen Chi, and Lijun Guo. "Efficient charge separation and enhanced photocurrent of CdTe quantum dots-Au nanoclusters composite with type-II band alignment." Applied Physics Letters 120, no. 14 (April 4, 2022): 143902. http://dx.doi.org/10.1063/5.0083889.

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Quantum dots (QDs)-based composites are promising candidates for optoelectronic and photonic devices. Understanding the photo-induced carrier dynamics is fundamental and crucial for improving the photoelectric conversion efficiency of nanocomposites. In this work, we have constructed nanocomposite hybridizing CdTe QDs with Au nanoclusters (Au NCs) and investigated the ultrafast carrier dynamics and enhanced photoelectric properties. The concurrent photoluminescence quenching and lifetime decreasing of CdTe QDs and Au NCs suggest a type-II band alignment, facilitating the carrier dynamics in the CdTe QDs-Au NCs' nanocomposite. The transient absorption measurements demonstrate an ultrafast and efficient electron transfer from CdTe QDs to Au NCs, effectively promoting the charge separation and inhibiting the exciton recombination. We found that the quantum efficiency of hot electron transfer can reach ∼50% with a rate constant of 1.01 × 1013 s−1 for the CdTe QDs-Au NCs' nanocomposite. As a result, the photocurrent performance of the CdTe QDs-Au NC device has been dramatically enhanced due to the efficient separation of photogenerated carriers, compared to that of individual CdTe QDs and Au NCs. These findings are significant for developing the light-harvesting and photoelectric devices based on semiconductor QDs and metal NCs.

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Wu, Chang, Yan Li, Zhengyao Xia, Cheng Ji, Yuqian Tang, Jinlei Zhang, Chunlan Ma, and Ju Gao. "Enhancing Photoluminescence of CsPb(ClxBr1−x)3 Perovskite Nanocrystals by Fe2+ Doping." Nanomaterials 13, no. 3 (January 28, 2023): 533. http://dx.doi.org/10.3390/nano13030533.

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The doping of impurity ions into perovskite lattices has been scrupulously developed as a promising method to stabilize the crystallographic structure and modulate the optoelectronic properties. However, the photoluminescence (PL) of Fe2+-doped mixed halide perovskite NCs is still relatively unexplored. In this work, the Fe2+-doped CsPb(ClxBr1−x)3 nanocrystals (NCs) are prepared by a hot injection method. In addition, their optical absorption, photoluminescence (PL), PL lifetimes, and photostabilities are compared with those of undoped CsPb(Br1−xClx)3 NCs. We find the Fe2+ doping results in the redshift of the absorption edge and PL. Moreover, the full width at half maximums (FWHMs) are decreased, PL quantum yields (QYs) are improved, and PL lifetimes are extended, suggesting the defect density is reduced by the Fe2+ doping. Moreover, the photostability is significantly improved after the Fe2+ doping. Therefore, this work reveals that Fe2+ doping is a very promising approach to modulate the optical properties of mixed halide perovskite NCs.

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Sekerbayev, Kairolla, Yerzhan Taurbayev, Gauhar Mussabek, Saule Baktygerey, Nikolay S. Pokryshkin, Valery G. Yakunin, Zhandos Utegulov, and Victor Yu Timoshenko. "Size-Dependent Phonon-Assisted Anti-Stokes Photoluminescence in Nanocrystals of Organometal Perovskites." Nanomaterials 12, no. 18 (September 14, 2022): 3184. http://dx.doi.org/10.3390/nano12183184.

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Anti-Stokes photoluminescence (ASPL), which is an up-conversion phonon-assisted process of the radiative recombination of photoexcited charge carriers, was investigated in methylammonium lead bromide (MALB) perovskite nanocrystals (NCs) with mean sizes that varied from about 6 to 120 nm. The structure properties of the MALB NCs were investigated by means of the scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. ASPL spectra of MALB NCs were measured under near-resonant laser excitation with a photon energy of 2.33 eV and they were compared with the results of the photoluminescence (PL) measurements under non-resonant excitation at 3.06 eV to reveal a contribution of phonon-assisted processes in ASPL. MALB NCs with a mean size of about 6 nm were found to demonstrate the most efficient ASPL, which is explained by an enhanced contribution of the phonon absorption process during the photoexcitation of small NCs. The obtained results can be useful for the application of nanocrystalline organometal perovskites in optoelectronic and all-optical solid-state cooling devices.

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Zeng, Yong-Tang, Zhan-Rong Li, Sheng-Po Chang, Arjun Ansay, Zi-Hao Wang, and Chun-Yuan Huang. "Bright CsPbBr3 Perovskite Nanocrystals with Improved Stability by In-Situ Zn-Doping." Nanomaterials 12, no. 5 (February 24, 2022): 759. http://dx.doi.org/10.3390/nano12050759.

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In this study, facile synthesis, characterization, and stability tests of highly luminescent Zn-doped CsPbBr3 perovskite nanocrystals (NCs) were demonstrated. The doping procedure was performed via partial replacement of PbBr2 with ZnBr2 in the precursor solution. Via Zn-doping, the photoluminescence quantum yield (PLQY) of the NCs was increased from 41.3% to 82.9%, with a blue-shifted peak at 503.7 nm and narrower spectral width of 18.7 nm which was consistent with the highly uniform size distribution of NCs observed from the TEM image. In the water-resistance stability test, the doped NCs exhibited an extended period-over four days until complete decomposition, under the harsh circumstances of hexane-ethanol-water mixing solution. The Zn-doped NC film maintained its 94% photoluminescence (PL) intensity after undergoing a heating/cooling cycle, surpassing the un-doped NC film with only 67% PL remaining. Based on our demonstrations, the in-situ Zn-doping procedure for the synthesis of CsPbBr3 NCs could be a promising strategy toward robust and PL-efficient nanomaterial to pave the way for realizing practical optoelectronic devices.

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Carolan, Darragh, and Hugh Doyle. "Size Controlled Synthesis of Germanium Nanocrystals: Effect of Ge Precursor and Hydride Reducing Agent." Journal of Nanomaterials 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/506056.

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Germanium nanocrystals (Ge NCs) have attracted increasing attention as a promising alternative to II–VI and IV–VI semiconductor materials as they are cheap, “green,” electrochemically stable, and compatible with existing CMOS processing methods. Germanium is a particularly attractive material for optoelectronic applications as it combines a narrow band gap with high carrier mobilities and a large exciton Bohr radius. Solution-phase synthesis and characterisation of size monodisperse alkyl-terminated Ge NCs are demonstrated. Ge NCs were synthesised under inert atmospheric conditions via the reduction of Ge halide salts (GeX4) by hydride reducing agents within inverse micelles. Regulation of NC size is achieved by variation of germanium precursor and the strength of hydride reducing agents used. UV-Visible absorbance and photoluminescence spectroscopy showed strong significant quantum confinement effects, with moderate absorption in the UV spectral range, and strong emission in the violet with a marked dependence on excitation wavelength.

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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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Shankar, Hari, William W. Yu, Youngjong Kang, and Prasenjit Kar. "Significant boost of the stability and PLQYof CsPbBr3 NCs by Cu-BTC MOF." Scientific Reports 12, no. 1 (May 12, 2022). http://dx.doi.org/10.1038/s41598-022-11874-6.

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AbstractDeveloping stable perovskite nanocrystals (NCs) with enhancing luminescent properties holds great importance for future potential applications in optoelectronics. Here, we engaged perovskite NCs in Cu2+ ion-based metal–organic framework (MOF) Cu-BTC (BTC = 1,3,5-benzene tricarboxylate) by physical mixing of MOF with CsPbBr3 NCs in toluene solution. MOF-protected perovskite NCs achieved high photoluminescence quantum yield 96.51% than pristine state CsPbBr3 NCs (51.66%). Along with the improvement in optical properties, the long-term stability of CsPbBr3 NCs in the solution phase also increases considerably upon loading in Cu-BTC MOF. Moreover, the changes in the luminescent intensity of the samples have been observed for 3 months in the solution. After 1 month, pristine CsPbBr3 NCs lose their emission intensity 68% from the initial, while the MOF-protected CsPbBr3 NCs show only a 10% reduction from the initial. These results indicate that the effective passivation of Cu-BTC MOF inhibits the aggregation of NCs, protecting them from the defective atmosphere. The excellent photoluminescence findings provide a new pathway for future optoelectronic applications.

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Journal articles on the topic 'Optoelectronics - NCs'

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