bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Keynote) Engineering Lead Halide Perovskite Nanocrystals for Fast Single-Particle and Collective Light Emission
Authors: Kovalenko Maksym V. 
Published: August 2024

Colloidal lead halide perovskite (LHP) nanocrystals (NCs), with bright and spectrally narrow photoluminescence (PL) tunable over the entire visible spectral range, are of immense interest as classical and quantum light sources. Fast (bright) and pure single-photon emission is key for many quantum technologies, from optical quantum computing to quantum key distribution and quantum imaging.The brightness of an emitter is ultimately described by Fermi’s golden rule, with a radiative rate proportional to its oscillator strength (intrinsic emitter property) times the local density of photonic states (photonic engineering, i.e. cavity). With perovskite NCs, we present a record-low sub-100 ps radiative decay time for CsPb(Br/Cl)3, almost as short as the reported exciton coherence time, by the NC size increase to 30 nm. The characteristic dependence of radiative rates on QD size, composition, and temperature suggests the formation of giant transition dipoles, as confirmed by effective-mass calculations for the case of the giant oscillator strength. Importantly, the fast radiative rate is achieved along with the single-photon emission despite the NC size being ten times larger than the exciton Bohr radius.
NC self-assembly is a versatile platform for materials engineering, particularly for attaining collective phenomena with perovskite NCs, such as superfluorescence in perovskite NC superlattices. Thus far, LHP NCs have been co-assembled with building blocks that acted solely as spacers to promote the tuning of the mutual arrangement of LHP nanocubes [2]. However, the functionality of the second SL component can give rise to the enhancement of the LHP NCs properties or the emergence of new collective effects. We present the formation of multicomponent SLs made from the CsPbBr3 NCs of two different sizes. The diversity of obtained SLs encompassed the binary ABO6-, ABO3-, and NaCl-type structures, all of which contained orientationally and positionally confined NCs. For the selected model system, the ABO6-type SL, we observed efficient NC coupling and Förster-like energy transfer from strongly confined 5.3 nm CsPbBr3 NCs to weakly confined 17.6 nm CsPbBr3 NCs. Exciton spatiotemporal dynamics measurements reveal that binary SLs exhibit enhanced exciton diffusivity compared to one-component SLs across the entire temperature range (from 5 K to 298 K). Observed incoherent NC coupling and controllable excitonic transport within the solid NC SLs hold promise for potential applications in optoelectronic devices.
[1]C. Zhu, S. C. Boehme, L. G. Feld, A. Moskalenko, D. N. Dirin, R. F. Mahrt, T. Stöferle, M. I. Bodnarchuk, A. L. Efros, P. C. Sercel, M. V. Kovalenko, G. Rainò. In review.
[2] Ihor Cherniukh et al. Nature, 2021, 593, 535–542.

[3] T. Sekh et al. Submitted
(Invited) Enhanced Catalysis of Surface-Activated Metallic WSe2 Nanosheets By Single-Atom Pt for High-Performance Li-O2 Battery
Authors: Jeong Sohee , Lee Gwang-Hee 
Published: August 2024

Layered materials, such as TMDCs, exhibit various electronic structures attributed to their polymorphism and can be further modificated at the atomic level through chemical treatments. TMDCs in the metallic phase (1T or 1T’ phase) have gained attention as efficient electrocatalystic materials, due to their exceptional transport properties compared to TMDCs in the semiconducting phase (2H phase). TMDCs with the metallic phase have been prepared by atomic-scale post-treatments, such as an intercalation and single-atom doping. However, the precise role of these post-treatments in the catalytic performance of TMDCs is still ambiguous, as it is uncertain whether the enhanced properties arise from charge transfer kinetics in metallic phase or electrochemical properties induced by the post-treatment.
Herein, we present a straightforward approach fabrication for fabricating metallic WSe2 nanosheets, which serve as an excellent support for single-atom Pt doping. The incorporation of single-atom Pt into WSe2 nanosheets was achieved using a simple solution method at room temperature. Extensive measurements were conducted, including XAS, XPS, and XPDF to investigate the local coordination structure of Pt-WSe2. These measurements confirmed the presentce of single-atom Pt doping within WSe2 layers. The introduction of single-atom Pt significantly enhanced the kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), leading to improved performance of Li-O2 batteries. Experimental measurements and DFT calculations provided evidence that the enhanced catalytic abilities of Pt-WSe2 originated from the improved interaction between oxygen and the Se vacancy on basal planes of WSe2. Consequently, the Li-O2 battery incorporating the Pt-WSe2 catalyst exhibited a stable discharge and charge cycle for up to 350 cycles, demonstrating its superior durability.
(Invited) In Situ and Operando Scattering Studies on Quantum Dot-Based Devices
Authors: Müller-Buschbaum Peter 
Published: August 2024

Colloidal quantum dots (QDs) made e.g. of PbS are attractive for various optoelectronic applications due to their tunable band gap with a large absorption wavelength range from the visible to the near-infrared region. Moreover, due to the high intrinsic permittivity, the exciton binding energy of PbS is smaller than in cadmium chalcogenide QDs and polymer materials, which is beneficial for devices driven by charge carrier generation and transport, e.g. photovoltaics and photodetectors.
In this work, we introduce wet chemical deposition methods beyond spin coating such as printing and spray deposition of QDs as a facile and potentially large-scale deposition method for high-performance photodetectors. The inner structures including the inter-dot distance of neighboring QDs and the structure, in the deposited QD solids, are studied by grazing-incidence small-angle X-ray scattering (GISAXS). In addition, the facet orientation of the QDs in the QD solids is characterized by grazing-incidence wide-angle X-ray scattering (GIWAXS). In particular, in situ GISAXS/GIWAXS studies during film formation are able to provide detailed information about the complex kinetic processes [1,2]. Operando GISAXS/GIWAXS studies on QD-based devices such as solar cells bring an in-depth understanding of the degradation mechanisms, which is key for improving the device stability and thereby bringing these novel materials into real-world applications [3]. Superlattice deformation in QD films on flexible substrates via uniaxial strain is followed in situ with GISAXS, providing a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates [4].

Nanoscale Horiz. 5, 880-885 (2020)

Nano Energy 78, 105254 (2020)

Energy Environ. Sci. 14, 3420-3429 (2021)

Mater. Horizon 8, 383-395 (2023)
(Invited) Electronic Trap Characterization in QD Devices Using Impedance Analysis Techniques
Authors: Park Taehwan , Hwang Gyuweon 
Published: August 2024

Colloidal quantum dots (QDs) are semiconductor nanocrystals with dimensions in the range of tens of nanometers. They exhibit unique optical and electronic properties, such as a size-dependent band gap and high absorption cross-section. These properties make them attractive for optoelectronic applications such as photovoltaics, light-emitting diodes (LEDs), and photodetectors. However, QD optoelectronics pose significant challenges due to trap states, which mainly originate from the surface states of nanocrystals. Therefore, it is necessary to analyze the trap states of QDs to understand their electronic properties and optimize their performance in optoelectronic applications. With this understanding, we want to correlate the cause of the trap states with the chemical defect to design better passivation strategies.
In this discussion, we will explore the principles of electronic trap analysis in colloidal quantum dots based on impedance analysis techniques as a complementary method to spectroscopy. We will provide examples of electronic trap analysis in PbS QD photovoltaics and InP QD LEDs to demonstrate the effectiveness of this approach. We can electrically probe the QD layers in the device using an impedance analyzer to analyze the energy level and density of trap states. By combining chemical analysis and a theoretical approach with this technique, we attempted to correlate the trap states and chemical defects.
Camphor-Based CVD Graphene Integrating CsPbBr3 Quantum Dots for High-Temperature Endurance, High Flexibility, and Fast Optical Switch Photodetection
Authors: HU Yu-CHI , You Ziran , Ci Ji-Wei , Hsiao Ming-Hsiang , Wang Chong-An , Tsai Meng-Lin , Chuang Chia-Shain , Tsai Dung-Sheng 
Published: August 2024

Photodetectors (PDs) based on camphor-based CVD graphene integrating CsPbBr3 quantum dots (QDs) have been fabricated on mica substrates successfully, showing temperature resistant, foldable, and fast response properties. The graphene synthesized from eco-friendly camphor was transferred onto mica substrates, and then the CsPbBr3 QDs were coated onto the graphene surface to form CsPbBr3 QDs/graphene composition on a flexible mica substrate.
According to the Raman spectrum, the structure of camphor-based CVD graphene is multilayer. The photoresponse of CsPbBr3 QDs/graphene composition was revealed by temperature-dependent (ranging from 300 K to 523 K) I-V measurements with/without white light illumination (light intensity: 112 mW/cm2). To highlight the temperature resistance of PDs based on CsPbBr3 QDs/graphene composition, a photo-to-dark current ratio (PDCR) of at 5 V is estimated at different temperatures. The PDCR of the CsPbBr3 QDs/graphene composition-based PD decreased from 3.2 to 0.74 with increasing temperature from 300 K to 523 K. Moreover, after 0 to 300 bending cycles, the vibration of PDCR value at 5 V is small (from 4.3 to 3.7), showing the high flexibility of the CsPbBr3 QDs/graphene composition-based PD. Furthermore, we found that the rise and fall times of the CsPbBr3 QDs/graphene composition-based PDs when we switched the illumination source ON and OFF are ~ 2 and ~1 ms, respectively, indicating fast optical switch behavior.
In this study, camphor-based CVD graphene incorporating CsPbBr3 QDs composition-based PD is demonstrated to exhibit high-temperature resistance, high flexibility, and fast response photodetection.
Keywords: Camphor, graphene, CsPbBr3 quantum dots, flexible photodetectors
Protective Layers to Improve the Durability of Lithium Anode
Authors: Peng Zhe , Wang Deyu 
Published: August 2024

Lithium metal anode possesses the advantages of high theoretic special capacity (3860 mAh g-1), low redox potential (-3.04 V vs. S.H.E.) and abundant lithium source. Therefore, tremendous efforts have been paid to explore the remedies of practical utilization. Its applications were seriously hindered by the severely side reactions between the electrolyte solvents and Li metal due to the mismatched energy-gap and large volumetric variation of lithium deposition layer. To address this challenge, various strategies were developed in whole world to prolong the operational life of lithium metal anode.
Our group focused on the development of Li+ filtrated membrane to isolate the fresh Li metal from the solvents. Firstly, we established the transplantable LiF-rich membrane via NiF2 film during formation to significantly improve the durability of lithium metal anode.[1] Then, we prepared a Li-filtrated film via a homemade stacked grapheme (SG), which possesses the higher Li nucleation over-potential than that on rational nano-structured copper scaffold (NCS-SG).[2] Additionally, an advanced SEI-functional membrane derived from LiF decorated SG were proposed to protect lithium anode by retarding electron transfer via C-Fx to avoid lithium deposition on the film surface.[3] Finally, the approaches on compatible electrolytes would be proposed.[4-5]

In summary, the durability of lithium metal anode could be significantly prolonged by the appropriate protective strategies.

Acknowledgement

This work was supported by the National Natural Science Foundation of China (Grant No. 22179052) and the Excellent Discipline Cultivation Project by JHUN (2023XKZ013).

Reference

[1] Z. Peng, N. Zhao, Z. Zhang, et al., Nano Energy, 2017, 39: 662-672.
[2] F. Ren, Z. Peng, M. Wang, et al., Energy Storage Materials, 2019, 16: 364-373.
[3] M. Wang, Z. Peng, D. Wang, Advanced Energy Mater., 2019, 1802912.
[4] Y. Qin, D. Wang, M. Liu, et al., ACS Appl. Mater. Interfaces, 2021, 13, 49445−49452.
[5] Y. Qin, D. Wang, Submitted to Advanced Mater.
A Direct Comparison of a Power and an Energy-Optimized Li-Ion Pouch Cell: Characterization, Ageing and Modelling
Authors: Wind Julia , Vie Preben J. S. , Ostrander John , Shearing Paul R 
Published: August 2024

Driven by the incredible transformation of the energy sector over the past 30 years lithium-ion batteries (LIBs) have seen continuous development and incredible improvements in terms of energy density, lifetime and power performance. Depending on their applications, Li-ion cells are normally optimized for either supplying as much power as possible or storing as much energy as possible, or a compromise between the two. A power optimized cell has typically a lower energy density and thinner electrode layers, compared to an energy optimized cell with higher energy density and thicker electrodes. One pathway to increase the performance of the modern LIBs is to move from conventional to thick electrode designs: this will result in an increased ratio of active components (anode/cathode) to inactive components (current collector, separator, casings) delivering improved energy densities. However, increasing the electrode thickness leads to several new challenges, such as e.g., reduced mechanical strength, higher tortuosity, and poorer rate performance, significantly affecting cell performance and ageing characteristics.
In this study we aim to develop a fundamental understanding of electrode performance and limitations through the evaluation of both, high-energy and high-power electrodes from state-of-the-art commercial LIBs. For this purpose, we selected two renowned large-scale commercial Li-ion pouch cells with similar geometry, chemistry, and capacity: one optimized for power and the other for energy.
Both cell types were tested following a test matrix including different temperatures, currents, and State-of-Charge limits as well as with and without mechanical compression of the cell during cycling. A large dataset with diagnostic data was recorded during ageing. This included, e.g., dQ/dV (Incremental capacity analysis, ICA), DC resistances and entropy changes. An especially strong influence of the current on the cycle life was observed for the energy-optimized cells. Cells without mechanical pressure had considerably shorter cycle life compared to cells cycled with mechanical pressure. Detailed monitoring of the pressure evolution across the pouch surface revealed significant pressure increases and thus electrode expansion throughout the cycling.
Cell-tear-down analysis was done to reveal differences in battery design, especially electrode structure and thicknesses. The extracted materials were structurally characterized by, e.g., SEM, XRD, and x-ray computed tomography, and assessed electrochemically in coin full- and half-cells. The obtained data was then used to fully parameterize a P2D electrochemical model.
The combination of detailed experiments coupled to P2D modelling provided valuable insights into influence of electrode thickness and morphology on battery performance and ageing, as well as degradation mechanisms specific to electrodes with increased thicknesses.
Modeling Pseudo-Capacitance as Parallel Electrochemical Reactions
Authors: Brady Nicholas 
Published: August 2024

Pseudo-capacitors are attractive electrochemical energy storage devices for their superior rate performance over conventional batteries, and higher energy storage capacity over traditional capacitors. Despite the importance of these types of devices, their hybrid physics makes it difficult to simulate their performance; as such, a general and well-established physics-based mathematical model does not exist. Using MnO2 as a model pseudo-capacitive electrode, this work describes the electrochemical performance of the MnO2 electrode as two parallel redox reactions with independent exchange-current densities and thermodynamic relationships. One of the reactions mimics the fast time-constant of the near-surface reaction (typical in a pseudo-capacitor), while the second reaction has a larger time-constant, characteristic of insertion reactions. Both redox reactions could be parameterized through Butler-Volmer kinetics, and the time-constant of each reaction was controlled by its exchange current density, , and the sensitivity of the thermodynamic potential to the charge passed, . Because of this model’s simplicity and reliance on well-established mathematical descriptions of electrochemical kinetics and mass-transfer, it may have utility in modeling pseudo-capacitors in general, not just MnO2. In addition, the mathematical descriptions of the physics can be directly implemented with porous electrode theory, which is more amenable to mathematical device and component optimization.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was supported by the LLNL-LDRD program under project 23-SI-002.
Impact of Fast-Charging Rates on Electrode Degradation in NMC/Gr Pouch Cells
Authors: Luo Mei , Gao Xiang , Mijailovic Aleksandar S , Wang Guanyi , Jansen Andrew N. , Yang Zhenzhen , Wu Qingliu , Sheldon Brian W. , Xu Jun , Lu Wenquan 
Published: August 2024

With the rapid expansion of the electric vehicles market, fast charging lithium-ion batteries has become increasingly imperative and inevitable. However, as fast-charging technologies entering electric vehicle market, persistent challenges related to safety issue and cell degradation, such as lithium dendrite growth, thermal runaway etc. necessitate meticulous consideration. In this study, we investigated fast-charging rate effects on electrode degradation in 1.6 Ah pouch cells using LiNi0.5Mn 0.3Co 0.2O2 cathode and graphite anode provided by Nanoramic Laboratories. Our investigation involves a comparative analysis of the aging behavior of NMC/Gr cells subjected to various charging rates — 0.5C, 2C, 4C, and 6C. Notably, we observed that pouch cells charged at rates of 0.5C and 2C could persist 80% capacity retention over 1000 cycles while cells using 4C and 6C can survive no more than 400 cycles with 80% retention. Through a series of post-mortem characterizations, including electrochemical impedance spectroscopy (EIS), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), we scrutinized the harvested NMC and graphite electrodes. As expected, more dendrite formation was observed on graphite anodes with 4C and 6C fast charging rates. The deterioration of cell performance primarily resulted from the degradation of the graphite anode. This degradation could be attributed to distinct dendrite morphologies at the graphite anode under varying charging rates (see Fig. 1). In addition to dendrite formation on graphite electrodes, we observed more severe pulverization of NMC secondary particles under higher charging rates despite their lower cycle numbers. This investigation provides a comprehensive understanding of how NMC and graphite degrade under different charging rates, offering valuable insights into the practical impacts of charging rates on cell lifespan and highlighting potential challenges that need to be addressed.
Acknowledgement
This material is based upon work supported by the U. S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Advanced Manufacturing Office, award number DE-EE0009111. Argonne National Laboratory is operated for DOE Office of Science by UChicago Argonne, LLC under contract number DE-AC02-06CH11357

Figure 1
Plasma Jet Mediated Reduction of Metal Salt
Authors: Lockwood Estrin Francis , Hagger Oliver S. J. , Parkes Michael A. , Sener M Emre , Caruana Daren J. 
Published: August 2024

We demonstrate electrodeposition where the plasma acts as both an electrolyte and electrode, to deposit metallic conductive coatings. In conventional electroplating metal ions are reduced at a working electrode with an applied electrochemical potential. Here an RF atmospheric pressure plasma jet (APPJ) is able to induce a electrochemical reduction due to the presence of free electrons. The advantage of this method is demonstrated by the ability to deposit conducting metal tracks on delicate surfaces including insulators and polymers. The small size and gaseous nature of the plasma allows deposition in difficult geometries with precise spatial control.
The reduction process occurs within the plasma. As the aerosolized metal salt crystals interact with the plasma, the free electrons reduce the metal and the hydrogen combines with the anion producing a water soluble acid. The metal reduction takes place within the plasma jet, as show by varying the plasma power and determining the amount of zerovalent metal deposited. Even at low powers, <6 W, the plasma was able to fully reduce the silver, however the copper requires plasma powers of 12 W and above in order to be fully reduced. Once reduced the deposited tracks were shown to be conductive with around 20 % and around 5 % of bulk conductivity for silver and copper respectively. A sintering process occurs also within the plasma, leaving a contiguous track of fused particles of zerovalent metal producing the conducting tracks. The technique is demonstrated mainly for copper and silver, however multiple other metals were capable of being deposited. In addition to the conductivity, the track adherence was tested both using a Scotch Tape© pull test and an in-house constructed scratch test. The track was completely unaffected by the tape pull and the stylus type scratch test showed that the films were scratch resistant up to a pressure up to of 420 kg cm-2, with no measurable drop in conductivity.
The APPJ is an accessible, low power, sustainable, precise electroplating device, capable of depositing pure metallic films onto a variety of surfaces. Furthermore, we demonstrate deposition on rough surfaces such as damaged fiberglass, as well as sensitive surfaces including plant tissue and pigskin, with limited damage to the surface.
Figure 1. a) showing the deposition setup including nebuliser, salt solution injection, gas flow and power supply. An optical image of the APPJ during deposition operation is included, as well as Schlieren imagine showing the laminar gas flow. b) A silver Hilbert curve printed onto Kapton 0.05 mm thickness via the plasma deposition technique, in a single step process, with no sample prep or post processing. c) Copper deposited on porcine skin showing conductance as part of a LED circuit.

Figure 1