bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated Silver-Zinc Fiber Battery Fabrication
Authors: Raj Abhishek , Kim Andrew , Steingart Daniel A
Published: February 2020

Flexible electronics play host to a wide array of applications, ranging from wearable devices to large scale systems. Improvements in battery energy density while maintaining safe and stable operation under mechanical deformation is key in advancing the success of these flexible electronic systems. Currently, the majority of flexible batteries are fabricated as planar devices in which the electrodes and separator are stacked in sheets. These devices are limited due to their ability to only bend biaxially and the fact that repeated biaxial bending stresses often result in delamination or cracking of the battery components which is impractical for wearable devices. Batteries in a cable configuration have been proposed as an alternative to planar architectures; this form factor offers the ability for multi-directional bending and promises applications in woven textiles and washable electronics. The current process for fabricating such batteries as described in literature involves separate manual stages of plating the anode on a wire substrate, synthesizing an electrolyte and coating it around the anode, wrapping the cathode and packaging the final device with shrink tubing. This handmade approach to fabrication can vary between research groups and is not suitable for scaling to meet industry production levels; accordingly, such a process would be greatly benefitted by high throughput automation.

In the current work, we demonstrate a modular automated system for the fabrication of a secondary Ag/Zn wire battery; such automation enables rapid prototyping in a roll to roll compatible process for the testing and fabrication of new chemistries for flexible battery systems. Moreover, pipeline fabrication ensures repeatability of fabricated devices and offers a more streamlined approach to manufacturing. In our work, 3D printed parts are used with low-cost Arduino microcontrollers to feed a carbon fiber wire through a sequence of dip coating baths in order to synthesize the Zn anode and coat it in a polymer electrolyte which is safer for wearable applications than organic electrolyte alternatives. The next stage encases the cable with the Ag cathode before the device is packaged in chemically resistive tubing and passed through the final dip coating bath of a liquid electrolyte. The desired length of cable is then cut and sealed. Characterization of the wire batteries is reported based on SEM analysis, strain cycling, charge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy in order to demonstrate the successful realization of a fiber battery based on our automated process. Performance metrics from these analyses such as discharge capacity and capacity retention is also compared to performance reported in literature for similar cable architectures.
Rapid Processing of Multi-Layered Iron Electrodes for Low-Cost Alkaline Batteries
Authors: Barnes Alistair David , Glover Carol Frances , Subramanian Raman , Sullivan James , Marinaccio Jordan Domonic , Williams Geraint , Elvins Jonathon
Published: February 2020

Iron electrodes are known for their long cycle life and long term stability, yet have received little attention in recent years[1]. Modern electrode manufacture techniques are investigated in order to produce a low-cost iron electrode capable of scale up. Cyclic voltammetry and scanning electrochemical techniques are used to characterise the electrodes.

In this study, Near Infrared (NIR) radiative heating is used to cure screen-printable iron containing inks in seconds as opposed to 10’s of minutes via traditional convection heating routes. This reduction in processing time is vital to enable rapid roll-to-roll manufacture of large-scale electrodes. This development allows production of a modular device with inherent safety, exceptional lifetime yet at a low cost.

Additionally, performance of these electrodes is improved through novel layering of active material[2]. A compact layer of active material adjacent to the current collector allows for capacity, whilst a diffuse layer surrounds this in order to improve high power performance through increased accessible surface area. Efficiency of the electrodes is improved through use of additives previously reported by Manohar et al to combat the parasitic hydrogen evolution reaction which occurs upon charge[3], [4].

Performance is analysed using traditional physical and electrochemical techniques, including full cell cycling with commercial Ni cathodes. Scanning electrochemical techniques, more typical in corrosion studies, have been employed in a novel manner to investigate surface current densities in order to identify how regions of varying thickness and density effect rate capability.

References:

[1] T. Reddy, Linden’s Handbook of Batteries, 4th ed. McGraw-Hill Professional, 2010.

[2] V. I. Chani, Q. Yang, D. S. Wilkinson, and G. C. Weatherly, “Effect of substrate pre-coating on adhesion of sintered nickel plaques for electrode application in rechargeable batteries,” J. Power Sources, vol. 142, no. 1–2, pp. 370–381, Mar. 2005.

[3] A. K. Manohar, S. Malkhandi, B. Yang, C. Yang, G. K. S. Prakash, and S. R. Narayanan, “A High-Performance Rechargeable Iron Electrode for Large-Scale Battery-Based Energy Storage,” J. Electrochem. Soc., vol. 159, no. 8, pp. A1209–A1214, Jan. 2012.

[4] A. K. Manohar, C. Yang, S. Malkhandi, G. K. S. Prakash, and S. R. Narayanan, “Enhancing the Performance of the Rechargeable Iron Electrode in Alkaline Batteries with Bismuth Oxide and Iron Sulfide Additives,” J. Electrochem. Soc., vol. 160, no. 11, pp. A2078–A2084, Jan. 2013.
In-Situ Liquid Cell TEM Study of Lithium Electrodeposition: Observation of Root- and Tip-Growth Mode
Authors: Kushima Akihiro , Bai Peng , Kuriyama Nariaki , Maebashi Takanori , Fujiwara Yoshiya , Bazant Martin Z. , Li Ju
Published: February 2020

In this work we conducted in-situ liquid-cell TEM experiments to observe the lithium electrodeposition process. We observed root-grown whiskers and tip-grown mossy clusters depending on the applied overpotentials. At the initial stage of the deposition, small spherical lithium nucleus emerges on the electrode surface. When high overpotential is used, the fast growing solid-electrolyte interface (SEI) layer on the lithium surface hinders the Li+ transport slowing down the deposition rate. However, stress may build up as Li continues to deposit inside the SEI confinement. When the stress reaches a threshold, the SEI can no longer sustain the stress and breaks near the current collector leading to the bursting growth of lithium from the root. The growth of lithium seizes again due to the SEI formation on the freshly grown lithium. This causes again the stress build-up and leads to another SEI breakage and root growth of a lithium whisker segment forming a kink. The thickness of the SEI on the whisker varies because of the time lag between the formations of the segments. This causes the area near the root (or the latest deposition sites) to be the primary site of the dissolution, isolating the lithium towards the tip. The isolated lithium looses the electric connection and becomes the source of the irreversible capacity loss. On the other hand, lithium grows from the tip when lower overpotential was used because the deposition rate of the lithium is much faster than the electrolyte decomposition rate. Our observation implies the relationship between the rates of lithium deposition and the SEI formation is the important factor determining the tip- vs. root-growth mode, which can be controlled by designing electrolyte composition/concentration or depositing artificial SEI layers. Understanding of these processes may contribute to developing dendrite suppression methods under various conditions for creating high-performance and safe energy storage devices.
Unscented Kalman Filter-Based Online State-of-Charge Estimation in LiFePO4 Battery-Powered Electric Vehicles
Authors: Huang Boyan , Wang Chenxi , Zhu Zheng , Xiao Yegui
Published: February 2020

Lithium iron phosphate (LiFePO4) battery has gained popularity due to its desirable characteristics such as low pollution, long cycling life, large power density, high safety and relatively low production costs. The estimation precision of State of Charge (SoC) of lithium iron phosphate (LiFePO4) battery determines the life and working efficiency of energy storage system. In practical applications, the battery capacity deteriorates with temperature drift and charge/discharge cycles, which make the accurate estimation of SoC a challenging issue.

In this paper, a novel online estimation technique for SoC has been developed. Based on a simplified RC model, the Open Circuit Voltage (OCV) of the battery is calculated through two adaptive filtering stage, which is then used to determine the SoC via a dynamic OCV–SoC curve. In the first stage a variable step-size Least Mean Square (VSS-LMS) algorithm is employed to adaptively estimate the model parameters in real-time; in the second stage, an Unscented Kalman Filter (UKF) is used to estimate the OCV from the parameters. UKF can provide a more accurate and stable performance compared to Extended Kalman Filter at an equal computational complexity by utilizing deterministic sample points to calculate mean and covariance terms which are propagated through the true nonlinearity, without approximation. Further, the influence of polarization potential on OCV parameter measurement is analyzed and the averaged battery terminal voltage and current are introduced to avoid the large error of OCV estimate causing by the inconsistency of batteries. The impact of polarization over potential variation in battery capacity is eliminated through a smooth filter so as to achieve a stable online estimation process. Plenty of experiments under data acquisition systems with different precisions were carried out in order to confirm the effectiveness of the proposed system. The errors in estimating the battery’s SoC were below 2% compared to more than 5% and 9% in the case of using an extended Kalman filter and ordinary Kalman filter. The proposed SOC estimation method with its simplified model was transferred to DSP system also to verify the accuracy, simplicity and feasibility of SoC estimation for real-time application.
Enhancement of Cycle Stability and Durability in Secondary Zinc-Air Batteries By Optional Ion-Transporting Separator
Authors: Hwang Ho Jung , Kwon Oh Chan , Shul Yong Gun
Published: February 2020

Highly durable secondary zinc air batteries were developed using polypropylene (PP) membrane (Celguard 5550) coated with polymerized ionic liquid as separators. The anionic exchange polymer was synthesized copolymerizing 1-[(4-ethenylphenyl)methyl]-3-butyl-imidazolium hydroxide (EBIH) and butyl methacrylate (BMA) monomers by free radical polymerization for both functionality and structural integrity. The ionic liquid induced copolymer was coated on a commercially available PP membrane. The coat allows anionic transfer through the separator and minimizes the migration of zincate ions, which causes the loss of active sites by the formation of zinc oxide on the surface of the catalyst layer. Electrochemical Impedance Spectroscopy (EIS) during the cycle process elucidated the premature failure of cells due to the zinc cross over for the untreated cell and revealed a substantial importance must be placed in zincate control. Scanning electron microscopy (SEM) revealed significant decrease in the porosity of the coated film without large cell performance sacrifice. Energy dispersive x-ray spectroscopy (EDS) data revealed the copolymer coated separator showed less zinc element in the cathode electrolyte, indicating lower zinc permeation through the membrane. Ion Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis confirmed over 96% of zinc ion cross over was reduced. In our charge/discharge setup, the constructed cell with the ionic liquid induced copolymer casted separator exhibited drastically improved durability as the battery life increased more than 281% compared to the pure commercial PP membrane.
Ultrasonic Sonochemical Synthesis and Electrochemical Study of Na-Li-Ti-O Quaternary Anode Materials for Secondary Batteries
Authors: Ghosh Swatilekha , Barpanda Prabeer
Published: February 2020

Energy storage is a key sector propelling portable electronics, hybrid automobiles and grid storage sectors, where Li-ion and Na-ion batteries form the numero-uno devices. Design and development of new and robust anode (negative insertion) materials is crucial to realize safe and high-performance secondary batteries. While Fe/Mn/Co/Ni-based compositions rule the cathode chemistry, the anode materials are broadly based on carbon and Ti-based materials. For suitable Ti-based anodes, synthesis of nanostructured materials holds the key in realizing desirable electrochemical performance. The current work explores the Na-Li-Ti-O quaternary systems to study few Ti-based anode materials for rechargeable Li-ion and Na-ion batteries, namely Na2Li2Ti6O14 (1.3 V vs. Li+/Li), Li4Ti5O12 (1.5 V vs. Li+/Li), Na2Ti6O13 (2.5 V vs. Na/Na+) and Na2Ti3O7 (0.85 V vs. Na/Na+) prepared by energy-savvy ultrasonic sonochemical synthesis route.

The sonochemical synthesis of various Na-Li-Ti-O compounds was conducted at operating condition of 20 kHz-500 W by applying sonication for 10-30 min (at 25 °C) using various precursor ratios. The final products were obtained by thermal annealing of the obtained powder at 500-650 °C for short duration (ca. 1-2 h, in air). While conventional solid-state synthesis demands prolonged annealing (12-24 h), sonication-assisted method yielded desired phases with restricted annealing of 1-2 h. This energy-savvy synthesis route involving lower calcination temperature and duration delivers uniform, spherical and nanostructured products (ca. 50-200 nm) suitable for anode application in batteries. Near theoretical capacity was obtained with excellent cycling stability in all four Na-Li-Ti-O compounds. First principle DFT calculation was employed to determine the structural stability and diffusion barrier for Na-/Li-ion migration in these anode materials. The effect of various synthesis parameters on the structural, morphological and final electrochemical properties of these Ti-based anodes will be presented gauging their potential usage in Li-ion and Na-ion batteries.
Three-Dimensional Si-Based Composite Nanorods Array Applied in Energy Storage System
Authors: Li Jing , Yue Chuang , Yu Yingjian , Lin Wei , Zheng Mingsen , Kang Junyong
Published: February 2020

The rapid development of the integrated circuit (IC) and Micro/Nano-Electro Mechanical System (M/NEMS) technologies are promoting the continued emergence or commercialization of the miniaturized autonomous devices such as wireless sensor networks (WSN) in smart grid.[1-4] In order to operate independently, the micro/nano autonomous electronic devices must have onboard power supply. However, the battery miniaturization still can not keep pace with the size scaling-down of the CMOS electronic technologies, due to the poor electrochemical performance of the micro/nano batteries or the un-compatible battery fabrication process with the IC technologies. Currently, the transition from two dimensional (2D) to 3D rechargeable LIBs with better electrochemical properties in a small areal footprint was found to cope well with state-of-the art semiconductor technologies conceptually providing new opportunities for micro/nano power systems in the future. [5-7]

In this work, the electrochemical performances of 3D Si-based composite nanorod (NR) arrays buffered by TiN/Ti interlayer, which were fabricated by a cost-effective, wafer scale and Si compatible process, were demonstrated and systematically investigated as the anode in rechargeable batteries. Lithium/Sodium ion storage behaviors were experimentally and theoretically studied.

References:

[1]. Scott E. Thompson and Srivatsan Parthasarathy, materialstoday, 2006, 9, 20-25.

[2]. Yunhao Liu, Yuan He, Mo Li, IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, 24, OCTOBER 2013.

[3]. Jeffrey W. Long, Bruce Dunn, Debra R. Rolison, and Henry S. White, Chem. Rev., 2004, 104, 4463-4492

[4]. Timothy S. Arthur, Daniel J. Bates, Nicolas Cirigliano, Derek C. Johnson , Peter Malati, James M. Mosby, Emilie Perre, Matthew T. Rawls, Amy L. Prieto, and Bruce Dunn, MRS Bull., 2011, 36, 523-531.

[5]. Loïc Baggetto, Harm C. M. Knoops, Rogier A. H. Niessen, Wilhelmus M. M. Kessels, and Peter H. L. Notten, J. Mater. Chem.,2010, 20, 3703-3708.

[6]. Alireza Kohandehghan, Peter Kalisvaart, Kai Cui, Martin Kupsta, Elmira Memarzadeha, and David Mitlin, J. Mater. Chem. A, 2013, 1, 12850-12861.

[7]. Peter H.L. Notten, Fred Roozeboom, Rogier A.H. Niessen, and Loïc Baggetto, Adv. Mater., 2007, 19, 4564-4567.
A Study on the Thermal Behavior of an Ultracapacitor Module Comprising 136 Cells
Authors: Park Sung June , Yi Jaeshin , Shin Chee Burm , Choi Jongrak , Lee Ha-Young
Published: February 2020

Ultracapacitors, also known as supercapacitors, have the potential to meet the increasing power requirements of energy-storage systems for automotive applications. As compared to batteries, ultracapacitors offer a higher power density, higher efficiency, and longer shelf and cycle life. Because the performance of an ultracapacitor depends on temperature, it is important to calculate accurately the thermal behavior of a single ultracapacitor cell and the module composed of multiple ultracapacitor cells for the efficient and reliable systems integration of an ultracapacitor in automotive applications.

In this work, modeling is performed to study the thermal behavior of an ultracapacitor module. The ultracapacitor module is subject to the charge/discharge cycling with constant-current between 190V and 380V. The validation of the modeling approach is provided through the comparison of the modeling results with the experimental measurements.

Fig. 1 shows the schematic diagram of the ultracapacitor module composed of the 136 ultracapacitor cells (2.8V/350F) from LS Mtron Ltd. In Fig. 2, the variation of surface temperature with time from the experiment is compared with that from modeling during the charge-discharge cycles with the constant current of 10 A.

Figure 1
In-Situ Critical Pitting Temperature of Steels Using EC Noise
Authors: Garfias-Mesias Luis Francisco
Published: February 2020

This paper shows how Electrochemical Noise (EN) can be used to determine the Critical Pitting Temperature (CPT) of steels in chloride containing solutions. The work presented here shows, for the first time, simultaneous In-situ micro-visualization and electrochemical noise of steels in chloride containing environments. A real time video of the surface of the sample was recorded while electrochemical noise measurements were taken as the temperature was slowly increased to obtain the CPT. This methodology allowed the observation of metastable pitting, pit initiation and pit propagation in steels.
A Comparison of Potentiodynamic and Potentiostatic Electrochemical Test Methods for Resolving the Localized Corrosion Response of Heat Treated Al-Li-Cu Alloy 2099
Authors: Hanna Benjamin , Buchheit Rudolph , Yang Fan
Published: February 2020

The corrosion mechanisms for 3rd generation Al-Li-Cu alloy AA2099 were characterized based on the localized attack on the microstructure. Samples were subjected to a series of artificial heat treatments conducted at temperatures ranging from 120°C to 180°C for times ranging from 12 to 168 hours. The varying microstructures were analyzed using transmission electron microscopy (TEM) and electron diffraction spectroscopy (EDS), which characterized the secondary phase precipitates grown during artificial aging. The formation of the strengthening phase T1 (Al2CuLi) is of particular note due to its anodic behavior relative to the alloy matrix. This particle is prone to selective dissolution and dealloying and can dictate the morphology of localized corrosion depending on how it is distributed within the alloy.

Localized corrosion was induced via individual immersion tests that utilized a highly oxidizing NaCl/H2O2 aqueous solution. The extent and morphology of the corrosion was assessed by optical microscopy. Results showed that pitting attack was apparent on samples aged at lower temperatures and/or for shorter times, when growth of secondary phase precipitates is hindered. Intergranular corrosion (IGC) was observed for the time-temperature combinations that promoted such precipitate growth. As revealed from TEM analysis, these samples showed T1 precipitates localized along grain boundaries. However, as samples continued to age and T1 formation became prevalent in the matrix, IGC was reduced. This is attributed to a smaller potential difference between grain boundary T1 and the surrounding area. Potentiodynamic experiments were then performed to identify any change in the localized breakdown potentials among the heat treated samples. It was shown that the specimens susceptible to IGC displayed a lower breakdown potential than those susceptible to only pitting.

Additional electrochemical tests were performed to capture the transition from pitting to IGC and determine whether the transition is potential-dependent, time-dependent or a combination of both. Unlike other Al-Cu alloys scanned potentiodynamically through the region of passivity breakdown, AA2099 did not display a double breakdown potential that would have indicated separate breakdown events for pitting and IGC. However, potentiostatic tests conducted after the onset of pitting showed that this transition can be captured based on the total charge imparted on the alloy. Samples that exhibited the most severe IGC via the immersion tests required the smaller amount of imparted charge to initiate IGC from pits. This demonstrates that the progression from pitting to IGC is marked by a distinct temporal component.
Influence of Surface Nanoporus Structure on the Corrosion Fatigue of Type 316L Stainless Steel in Sodium Chloride Solution
Authors: Yamada Natsuko , Tsuchiya Hiroaki , Fujimoto Shinji
Published: February 2020

Corrosion fatigue is one of the severe corrosion problems that leads to materials failure. Therefore numerous works have been dedicated in order to improve fatigue life. For example, it was reported that the surface treatment such as shot-peening improved fatigue life of a low-alloy steel. This result indicates that the surface properties and morphology may affect the corrosion fatigue behavior.

Recently nanopore arrays have been reported to be fabricated on stainless steels in perchloric acid containing organic solvents. The dimension of nanopore is controlled by applied voltage.[1-3]

In the present work, we investigated the impact of surface morphology on corrosion fatigue behavior of type 316L stainless steel in a 0.9% NaCl solution.

3 types of samples with different morphologies were prepared; mirror-finished, electropolished and nanoporus samples. In the sodium chloride solution, the fatigue test was performed to evaluate the effect of the surface morphology on fatigue life. Furthermore, fractured samples were observed by a scanning electron microscopy(SEM).

Results indicate that the surface morphology clearly affects on the fatigue life, that is, the presence of nanopore arrays improved fatigue life in the sodium chloride solution.

Details on influence of the surface nanoporus structure on the corrosion fatigue behavior will be discussed in the presentation.

[1]V.Vignal, J.C.Roux, S.Flandrois, A.Fevrier, Corrosion Science.42(2000)1041

[2]F.Martin, D.Del Frari, J.Cousty, C.Bataillon, Electrochimica Acta 54(2009)3086

[3]H.Tsuchiya, T.Suzumura, Y.Terada, S.Fujimoto, Electrochimica Acta 82(2012)333
A Smart-Release Corrosion Inhibitor Pigment for Galvanised Steel Based on Salicylaldoxime-Loaded Hydrotalcite
Authors: Ansell Phil , Williams Geraint , Dodds Patrick Charles , Glover Carol Frances , McMurray Hamilton Neil
Published: February 2020

Smart-release anticorrosion pigments are a promising alternative technology to traditional anticorrosive pigments such as sparingly soluble salts. Due to legislation prohibiting the use of chromium (VI) containing protective coatings, new environmentally friendly alternatives are required. Smart release pigments have numerous advantages over traditional pigment technologies. Sparingly soluble salts slowly leach out their constituent ions over time, which both reduces the lifetime of the coating and leads to environmental effects. In contrast, smart release pigments utilise ion-exchange properties to release inhibitor species on demand, whilst simultaneously sequestering corrosive species such as chloride ions. In this work intelligent release pigments based on anion-exchange hydrotalcite (HT) like materials were studied with respect to their efficiency in the inhibition of cathodic disbondment of a model coating. The ability of the various organic-anion loaded HT pigments to inhibit cathodic delamination of hot dip galvanised steel was evaluated using polyvinyl butyral (PVB) coatings containing a range of volume fractions of the inhibitive pigments. An in-situ Scanning Kelvin Probe (SKP) technique was used to measure the rate of delamination over time, by measuring time-dependent changes in free corrosion potential of the zinc surface under the organic coatings. Of the selection of organic anions evaluated, the most effective corrosion inhibitor was found to be salicylaldoxime, a well-known chelating reagent for various divalent metal cations. The slowing of cathodic delamination rates with increasing pigment volume fraction compared well with the performance of a hexavalent chromate-containing benchmark. To determine the importance of the release of salicylaldoxime from the coating into the electrolyte in contact with bare metal at a penetrative coating defect, experiments were also conducted using unpigmented PVB coatings in a situation where inhibitor additions were made to the initiating electrolyte. The conclusion of this investigation is that for the corrosion protection of galvanised steel surfaces, salicylaldoxime-loaded HT intelligent-release pigments represent effective, yet environmentally friendly alternatives to the current chromate containing coating technologies.
Flexible Crystalline Silicon Solar Cell with Vertically Aligned Microwire Arrays
Authors: Hwang Inchan , Um Han-Don , Seo Kwanyong
Published: February 2020

Much attention has been paid to thin crystalline silicon (c-Si) due to excellent flexible characteristics, stable performance, and possibility of high efficiency as a means for developing next generational flexible solar cells. Here, we confirm that the 50 µm thin c-Si with various length of microwire arrays (MWA) shows stable flexible characteristics regardless of MWA length. In our result, the fabricated flexible solar cells using 50 µm thin c-Si with 20 µm MWA exhibit power conversion efficiencies of up to 15.2% under AM 1.5G illumination with an open-circuit voltage of 576 mV and a short-circuit current density of 34.1 mAcm-2. Furthermore, to overcome the light reflection of flat-top-area of MWA, tapered MWA that can reduce surface reflection to around 1% is fabricated by simple wet-etching process. Applying the 20 µm tapered MWA on 50 µm thin c-Si, our flexible solar cell shows maximum efficiency of 16.8% and stable photovoltaic performance during bending tests up to 1000 times at the bending radius of 10 mm. Therefore, we believe that our proposed flexible solar cell can be a next-generation solar energy harvesting devices through high efficiency and stable flexibility.
(Invited) Inorganic Charge Transport Materials Grown By Atomic Layer Deposition for Highly Efficient and Long-Term Stable Perovskite Solar Cells
Authors: Seo Seongrok , Bae Changdeuck , Jeong Seonghwa , In Yongjae , Shin Hyunjung
Published: February 2020

Lead halide perovskite solar cells have recently attracted huge attention because of their dramatic rise in power conversion efficiency (PCEs) within few years. However, high PCEs have not been thoroughly guaranteed for long-term period of test under continuous illumination. Here, we report highly efficient perovskite solar cells having a long-term stability that adapts uniform and dense inorganic charge transport layer (NiO and Ti-S compounds) grown by atomic layer deposition (ALD) at relatively lower temperature. Ultra-thin un-doped NiO films, with much less absorption loss, were prepared by ALD with a highly precise control over the thickness. Thin enough (5 ~ 7.5 nm in thickness) NiO films with the thickness of few times of Debye length ( 1 ~ 2 nm for NiO) show enough conductivities achieved by overlapping space charge regions, which finally exhibited a highest PCE of 16.40 % with high open circuit voltage of 1.04 V and fill factor of 0.72 with a negligible current-voltage hysteresis. Furthermore, highly dense inorganic electron transport layer has been directly deposited onto perovskite using non-aqueous ALD process at room temperature, which ensures no degradation of perovskite. This inorganic layer demonstrated efficient electron transporting as well as highly passivating performance. Finally, perovskite solar cells that using inorganic charge transport layers with large area (> 10 cm2) were fabricated and their long-term stability under light soaking were characterized.
(Invited) Inverted Planar Heterojunction Perovskite Solar Cells Based on Lead Acetate Precursor with Efficiency Exceeding 18%
Authors: Zhu Rui
Published: February 2020

Organic-inorganic lead halide perovskites are emerging materials for the next-generation photovoltaics. Lead halides are the most commonly used lead precursors for perovskite active layers. Recently, lead acetate (Pb(Ac)2) has shown its superiority as the potential replacement for traditional lead halides. Here, we demonstrate a strategy to improve the efficiency for the perovskite solar cell based on lead acetate precursor. We utilized methylammonium bromide as an additive in the Pb(Ac)2 and methylammonium iodide precursor solution, resulting in uniform, compact and pinhole-free perovskite films. We observed enhanced charge carrier extraction between the perovskite layer and charge collection layers and delivered a champion power conversion efficiency of 18.3% with a stabilized output efficiency of 17.6% at the maximum power point. The optimized devices also exhibited negligible current density-voltage (J-V) hysteresis under the scanning conditions.
(Invited) Controlling Perovskite Structure and Grain Morphology for High-Performance Perovskite Solar Cells
Authors: Zhu Kai
Published: February 2020

Organometallic halide perovskites have recently emerged as a new class of light absorbers that have demonstrated a rapid progress and impressive efficiencies (>20%) for solar conversion applications. Despite the rapid progress demonstrated by these light absorbers, there is still a lack of understanding of some fundamental material/physical/chemical properties of these materials. In this presentation, I will present our recent studies toward a better understanding and control of perovskite nucleation, grain growth, and microstructure evolution using solution processing.1 The precursor chemistry and growth conditions are found to affect significantly the structural and electro-optical properties of perovskite thin films. Devices based on different grain sizes were investigated to correlate the grain sizes with device performance. The impact of grain size on charge carrier dynamics was also studied. Although we used the standard TiO2/perovskite/spiro-MeOTAD sandwich structure, we found evidence of a p-n junction rather than the commonly reported p-i-n structure for our studied devices.2 In addition, I will briefly discuss our recent investigation on stabilizing perovskite structures by tuning tolerance factor through solid state alloying.3 These results and others will be discussed.

References

1 M. Yang, Y. Zhou, Y. Zeng, C.-S. Jiang, N. P. Padture, K. Zhu, Adv. Mater. 27, 6363 (2015).

2 C.-S. Jiang, M. Yang, Y. Zhou, B. To, S. U. Nanayakkara, J. M. Luther, W. Zhou, J. J. Berry, J. van de Lagemaat, N. P. Padture, K. Zhu, M. M. Al-Jassim, Nature Commun.
6, 8937 (2015).

3 Z. Li, M. J. Yang, J. S. Park, S. H. Wei, J. J. Berry, K. Zhu, Chem. Mater. 28, 284 (2016).
Charge Accumulation Mechanisms Under Dark in Perovskite Solar Cells
Authors: Ripolles Teresa S. , Baranwal Ajay K. , García-Belmonte Germà , Hayase Shuzi
Published: February 2020

Nowadays, organic-inorganic hybrid perovskite solar cells have emerged rapidly in over few years due to their impressive improvements in the photoconvertion efficiencies exceeding 21%.1 This technology has become an alternative to the conventional photovoltaic devices, such as Silicon Solar Cells which consume a large portion of the market. In spite of their powerful features, for instance: high absorbance and long-range balanced charge transport lengths within hybrid perovskites,2 there are still some issues that are complete unknown. The electrical processes such as carrier transport into the perovskite film and charge extraction at the interfaces as well as electric field that occurs in the timescale of seconds are still under debate.3 Particularly, we found a new current peak at forward bias in the current-voltage curves under dark for the standard mesoscopic perovskite solar cells. This shape only appears at reverse scan (RS) direction and when the solar cells were kept for several seconds at short-circuit conditions before starting the RS measurement. If the device remains at forward conditions, the mentioned peak disappears. To that end, several hole transport materials (Spiro-OMeTAD and P3HT) and perovskite absorbers with different organic/inorganic cations (CH3NH3PbI3 and CsPbI3) were analyzed in a complete mesoporous-TiO2 photovoltaic devices. We considered that shallow and/or deep traps states located at interface either perovskite/p-type or perovskite/n-type transport materials should be filled.

References

1 J. H. Noh, S. H. Im, J. H. Heo, T. N. Mandal, and S. I. Seok, Nano Lett. 13 (4), 1764 (2013).

2 B. Wu, K. W. Fu, N. Yantara, G. C. Xing, S. Y. Sun, T. C. Sum, and N. Mathews, Adv. Energy Mater. 5 (19), 8 (2015).

3 H. S. Duan, H. P. Zhou, Q. Chen, P. Y. Sun, S. Luo, T. B. Song, B. Bob, and Y. Yang, Phys. Chem. Chem. Phys. 17 (1), 112 (2015); X. D. Li, X. Y. Wang, W. J. Zhang, Y. L. Wu, F. Gao, and J. F. Fang, Org. Electron. 18, 107 (2015).
Stabilizing Hybrid Perovskites Via Non-Hydrolytic Atomic Layer Deposited Overlayers
Authors: Kim In Soo , Martinson Alex B. F.
Published: February 2020

A significant challenge to the practical application of hybrid perovskites remains for photovoltaic application. Specifically, the presence of hygroscopic ionic small molecules – alkylammonium cations – has been identified as a primary source of the absorber's sensitivity towards any moisture and any temperatures greater than 150 °C. CH3NH3PbI3 , for instance, rapidly degrades upon exposure to modest relative humidity even at room temperature via:

CH3NH3PbI3(s) → PbI2(s) + CH3NH3I(aq)

A related, but distinct, decomposition pathway is induced by heating above 150 °C even under an inert and dry environment, where methylamine and hydroiodic acid have measurable vapor pressure:

CH3NH3PbI3(s) → PbI2(s) + CH3NH2↑ + HI↑

Various attempts have been made to improve system stability including modification of chemistry, two dimensional (2D) hybrid perovskites, and macroscopic encapsulation. While these measures may slow degradation the effect is often modest, transient, and adds significant device complexity. Synthetically-compatible, pinhole-free functional overlayers, in contrast, would provide a simple route to surface chemical passivation as well as a physical barrier to diffusion in or out of the active layer. Atomic Layer Deposition (ALD) is a vapor-phase deposition technique with the capability to produce ultra-thin and pinhole-free films with well-defined surface chemical control and precise physical thickness, providing a good match to these challenges. However, the vast majority of oxide ALD processes invoke water (H2O), hydrogen peroxide (H2O2) or ozone (O3) as oxygen sources, often at temperatures greater than 150 °C. Unfortunately, these chemicals and temperatures are predicted to be in direct conflict with most hybrid perovskite halides and therefore may preclude an integrated overlayer approach. However, we report low temperature non-hydrolytic (i.e. waterless) ALD to establish stabilizing overlayers of Al2O3 or TiO2 directly on CH3NH3PbI3−xClx films. We demonstrate not only that oxide ALD conditions exist that are compatible with hybrid perovskite halides, but that the resulting systems exhibit dramatically improved stability against moisture (85% RH) and enhanced resistance to considerably higher temperatures (up to 250 °C) and even liquid water. We further demonstrate the capability of nh-TiO2 to serve a dual role – stabilizing the absorber underlayer and accepting electrons in future inverted photovoltaics.

The figure shows the effect of a liquid water drop after two minutes directly on a perovskite halide thin film, without and with an ultrathin hybrid ALD passivation layer.

Figure 1
Enhancement in Efficiency of Hybrid Polymer Solar Cells By CdSe Quantum Dot Doping
Authors: Kumari Kusum , Chand Suresh
Published: February 2020

Polymer solar cells (PSC) is a current frontier international research and development area owing to inherent advantages in these devices[1-5]. It includes cost effectiveness, flexibility, easy processibility, large area applications etc. Power conversion efficiency of ~ 10 % have already been achieved in bulk-heterojunction solar cells in single cell geometry and more than 11% in tendom configuration[8.9]. One of the limitations in the commercialization of this photovoltaic technology is the stability issue. To address both the efficiency and stability in these devices, there is another promising approach wherein inorganic semiconductor quantum dots are doped in polymer donor-acceptor composite matrix[6.7]. The advantage of these hybrid devices is that the inorganic components viz. quantum dots provide stability and enhanced mobility of charge carrier in the nanomatrix which in turn results in increase in efficiency as well. In this work we demonstrate the effect of Cadmium Selenide (CdSe) quantum dots (size~5nm) doping in poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM), and 2-methoxy-5-(2-ethylhexyloxy)-polyphenylenevinylene (MEH-PPV): PCBM bulk heterojunction matrix where it results in considerable enhancement in efficiency in these devices. In fact the devices have been made in ambient air rather than in inert glove box conditions to illustrate conceptually the effect of CdSe quantum dots where it results in the enhancement of efficiency from 1.3 to 2% for P3HT:PCBM matrix, and 0.6 to 1.5 % for MEH-PPV:PCBM matrix. This enhancement of efficiency on CdSe quantum dot doping has been attributed to the pivotal role played by CdSe quantum dots viz. (i) it results in faster separation of excitons at donor-acceptor interface, (ii) it enables the faster transport of electrons after separation and their subsequent extraction/collection at the electrodes. This work owes promise for developing further cost effective, better efficient and stable hybrid polymer solar cells.

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Sih-Hao Liao, Hong-Jyun Jhuo, Po-Nan Yeh, Yu-Shan Cheng, Yi-Lun Li, Yu-Hsuan Lee, Sunil Sharma & Show-An Chen, SCIENTIFIC REPORTS (2014) 4 : 6813.

By Yongye Liang, Zheng Xu, Jiangbin Xia, Szu-Ting Tsai, Yue Wu, Gang Li,*Claire Ray, and Luping Yu, Adv. Mater. 22 (2010) E135–E138.
Surface Passivation of Lead Sulfide Nanocrystalswith Low Electron Affinity Metals:Photoluminescence and Photovoltaicperformance
Authors: Tavakoli Mohammad Mahdi , Tavakoli Rouhollah , Fan Zhiyong , Simchi Abdolreza
Published: February 2020

During the last decade, solution-processed colloidal quantum dots (CQDs) have attracted significant

attention for low-cost fabrication of optoelectronic devices. In this study, lead sulfide (PbS) CQDs were

synthesized via the hot injection method and the effect of doping elements with low electron affinity,

including cadmium, calcium and zinc, on the passivation of trap states was investigated. A red-shift

in the luminescence emission was observed by doping through passivation of lead dangling bonds.

Time-resolved photoluminescence measurements showed that the lifetime of charged carriers was

significantly enhanced by cadmium doping (B80%) which is quite noticeable compared with calciumand

zinc-doped nanocrystals. External quantum efficiency measurements on thin solid films (B300 nm)

prepared by spin coating supported improved lifetime of carriers through passivation of mid-gap trap

states. In order to show the potential application of the doping process, bulk heterojunction CQD solar

cells were fabricated. It was found that the power conversion efficiency (PCE) was improved up to

B40%; the highest improvement was observed with the Cd treatment. Finally, density functional theory

(DFT) and electrochemical impedance spectroscopy (EIS) were employed to study the effect of doping

on the density of states. The results showed that doping with low electron affinity metals effectively

reduced the deep trap states of PbS QDs.

Figure 1
Tantalum Oxide Resistive Memory Devices By Ion Assisted Deposition
Authors: Goeke Ronald S. , Hughart David R. , Jacobs-Gedrim Robin Bay , Smith Carl L. , James Conrad D. , Marinella Matthew J.
Published: February 2020

Nano-ionic resistive memory devices are of significant interest as a high density storage-class memory, and well as in neuromorphic accelerator computing. For both of these applications, a key challenge is cycle to cycle (temporal) and device to device write variability. Highly uniform films with evenly distributed concentrations of oxygen vacancies are desired for this purpose. The switchable resistive properties of these resistive memory devices have been typically fabricated from sub-stoichiometric tantalum pentoxide using reactive sputtering of Tantalum metal with a mixture of Argon and Oxygen, which does not result in a highly uniform film. Alternatively, by using annealed stoichiometric atomic layer deposited films combined with a reducing metal layer a more uniform film is obtained, but the oxygen vacancy distribution cannot be precisely controlled. Using Ion Assisted Deposition (IAD), we have successfully made memristor devices with a significant improvement in yield and a significant reduction in device performance variability. The IAD deposition approach involves e-beam evaporation of tantalum metal with a reactive beam of argon and oxygen ions impinging upon the growing film. Using this technique, the oxide formation occurs at the substrate resulting in better control over film stoichiometry. IAD is a popular technique for the deposition of oxide thin films in the optical coating industry, but this is the first known usage of this technique for stoichiometry control of ReRAM thin films.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Figure 1
Silicon Oxide Reram Device
Authors: Mehonic Adnan , Buckwell Mark , Montesi Luca , Munde Manveer , Chater Richard John , McPhail David S , Bosman Michel , Kenyon Anthony Joseph
Published: February 2020

We demonstrate a silicon oxide redox-based resistive RAM (ReRAM) device. The resistance switching in our devices is intrinsic to changes within the oxide layer and thus it is not an effect of diffusion of metallic ions from the metallic electrode as in the case of electrochemical metallization (ECM) cells.

In addition to standard two-level switching we demonstrate a multi-level switching as well as an analogue modulation of resistance. It is possible to switch devices in both bipolar and unipolar switching modes while dynamically adjusting the device electronic properties, in particular two desirable properties: non-linearity in I-V curves and self-rectification. We demonstrate room temperature quantisation of conductance in our devices, implying ballistic transport of electrons through a quantum constriction, associated with an individual conductive filament in the oxide bulk.

Scanning tunnelling microscopy (STM), atomic force microscopy (AFM), and conductive atomic force microscopy (C-AFM) measurements provide a more detailed insight into both the location and the dimensions of the conductive filaments responsible for the resistance change.

Further, we demonstrate the field-driven movement of oxygen ions that causes large-scale changes in oxide layer that are accompanied with the oxygen release. We report on the material changes leading to resistance switching using secondary ion mass spectroscopy (SIMS), x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

Finally we demonstrate and discuss on the feasibility of using the ReRAM cell to model aspects of the electrical activity of the neuron that could provide a novel way of using ReRAM devices in neuromorphic systems.
The Interaction of SiOx-Based Resistive RAM Devices with Oxygen: Observations on Release and Absorption
Authors: Montesi Luca , Buckwell Mark , van den Bosch Celeste Anna Maria , Chater Richard John , Fearn Sarah , Mehonic Adnan , Aguadero Ainara , Kenyon Anthony Joseph
Published: February 2020

Novel storage technologies have emerged due to typical non-volatile memory approaching its scalability limit. A candidate under development is intrinsic filamentary oxide based Resistive RAM (ReRAM), which offers appealing scalability, standard process compatibility, data retention and power consumption. Device endurance remains an issue to be tackled before commercialization. To address this, we studied our TiN/SiOx/TiN (x<2) intrinsic switching devices, which belong to a family that develops unfavorable insulating “stains” on the top electrode during high-stress operation. We provide positive correlation of these stains with the release and incorporation of oxygen exchanging with the atmosphere. During high vacuum in situ operation, we detected O2 and O2
- emission through Secondary Ion Mass Spectroscopy (SIMS) and Residual Gas Analyzer (RGA) analyses. Following cycling in a labeled oxygen environment, we detected atmospheric oxygen incorporation through ToF-SIMS depth profiling, shedding light on how filamentation may occur. We also observed significantly altered electrical behavior in high vacuum, oxygen rich and nitrogen rich atmospheres. These findings provide evidence to improve endurance of future device through the use of oxygen sinks and sources.