Dense Absorber Research Articles

Wave-to-wire modelling and hydraulic PTO optimization of a dense point absorber WEC array

We investigate the hydrodynamic interactions and power extraction efficiency of a dense array of Point Absorber (PA) Wave Energy Converters (WECs) clustered around the fixed pillar of a wind turbine –the Ocean Grazer device– with a standard hydraulic Power Take-Off (PTO) system. Using potential flow theory, a detailed wave-to-wire model is developed in WEC-Sim with four distinct hydraulic PTO designs: i) Multi PTO-with individual hydraulic PTO systems for each buoy, ii) Shared PTO V1-with a unified PTO system for the entire array, iii) Shared PTO V2-with the accumulator volume split into two segments, and iv) Shared PTO V3-with four strategically distributed segments. Key parameters such as the diameter of the hydraulic pistons, volume and pre-charged pressure of the high-pressure accumulators, hydraulic motor displacement and the speed of the electric generator are optimized with a genetic algorithm and a parametric analysis across various sea states. The results highlight that strategically allocating the accumulators across the floaters of a dense WEC array can yield significantly higher power production and should be considered at the early design stages.

Opportunities, Challenges, and Strategies for Scalable Deposition of Metal Halide Perovskite Solar Cells and Modules

Hybrid organic‐inorganic perovskite solar cells (PSCs) have rapidly advanced in the new generation of photovoltaic devices. As the demand for energy continues to grow, the pursuit of more stable, highly efficient, and cost‐effective solar cells has intensified in both academic research and the industry. Consequently, the development of scalable fabrication techniques that yield a uniform and dense perovskite absorber layer with optimal crystallization plays a crucial role to enhance stability and higher efficiency of perovskite solar modules. This review provides a comprehensive summary of recent advancements, comparison, and future prospects of scalable deposition techniques for perovskite photovoltaics. We discuss various techniques, including solution‐based and physical methods such as blade coating, inkjet printing (IJP), screen printing, slot‐die coating, physical vapor deposition, and spray coating that have been employed for fabrication of perovskite modules. The advantages and challenges associated with these techniques, such as contactless and maskless deposition, scalability, and compatibility with roll‐to‐roll processes, have been thoroughly examined. Finally, the integration of multiple subcells in perovskite solar modules is explored using different scalable deposition techniques.

Printable High-efficiency and Stable FAPbBr3 Perovskite Solar Cells for Multifunctional Building-integrated Photovoltaics.

Perovskite solar cells (PSCs) show great promise for next-generation building-integrated photovoltaic (BIPV) applications because of their abundance of raw materials, adjustable transparency, and cost-effective printable processing. Owing to the complex perovskite nucleation and growth control, the fabrication of large-area perovskite films for high-performance printed PSCs is still under active investigation. Herein, wepropose an intermediate-phase-transition-assisted one-step blade coating for an intrinsic transparent formamidinium lead bromide (FAPbBr3 ) perovskite film. The intermediate complex optimized the crystal growth path of FAPbBr3 , resulting in a large-area, homogeneous, and dense absorber film. A champion efficiency of 10.86% with high open-circuit voltage up to 1.57V wasobtained with a simplified device architecture of glass/FTO/SnO2 /FAPbBr3 /carbon. Moreover, the unencapsulated devices maintained 90% of their initial power conversion efficiency after aging at 75°C for 1000h in ambient air, and 96% after maximum power point tracking for 500h. The printed semitransparent PSCs, with average visible light transmittance over 45%, demonstrated high efficiencies for both small devices (8.6%) and 10 × 10 cm2 modules (5.55%). Finally, the ability to customize the color, transparency, and thermal insulation properties of FAPbBr3 PSCs makes them high prospects as multifunctional BIPVs. This article is protected by copyright. All rights reserved.

Performance Enhancement in Powder-Fabricated Cu2(ZnSn)Se4 Solar Cell by Roll Compression.

Despite the improved conversion efficiency of Cu2(ZnSn)Se4 (CZTSe) solar cells, their roll-to-roll fabrication nonetheless leads to low performance. The selenization time and temperature are typically considered major parameters for a powder-based CZTSe film; meanwhile, the importance of the densification during the roll-to-roll process is often overlooked. The densification process is related to the porosity of the light-absorbing layer, where high porosity lowers cell performance. In this study, we fabricated a dense CZTSe absorber layer as a method of controlling the compression of a powder precursor (Cu1.7(Zn1.2Sn1.0)S4.0 (CZTS)) during the roll-press process. The increased particle packing density of the CZTS layer was crucial in sintering the powder layer into a dense film and preventing severe selenization of the Mo back electrode. The pressed absorber layer of the CZTSe solar cell exhibited a more uniform chemical composition determined using dynamic secondary ion mass spectrometry (SIMS). Under the AM 1.5G illumination condition, the power conversion efficiency of the pressed solar cell was 6.82%, while the unpressed one was 4.90%.

High photovoltaic efficiency CZTSSe thin film solar cells obtained by Li doping in air

Alkali metal doping is considered as an effective strategy in the pathway of improving the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic materials. In this paper, Li is successfully doped into CZTSSe films in air and high efficiency devices are obtained. By X-ray diffraction and scanning electron microscopy, it can be found that the crystalline quality of CZTSSe films after Li doping is effectively improved and full and dense absorber layer crystals are obtained. In addition, TRPL also shows that the carrier lifetime of CZTSSe by doping with Li is significantly enhanced. Lithium-doped CZTSSe thin-film solar cells finally achieve a high efficiency of 9.84%. This Li doping route with simple process and superior device performance obtained provides a new idea for further development of element-rich and non-toxic CZTSSe thin film materials.

RADiCAL—Precision Timing, Ultracompact, Radiation-Hard Electromagnetic Calorimetry

To address the challenges of providing high-performance calorimetry in future hadron collider experiments under conditions of high luminosity and high radiation (FCC-hh environments), we conducted R&D on advanced calorimetry techniques suitable for such operation, based on scintillation and wavelength-shifting technologies and photosensor (SiPM and SiPM-like) technology. In particular, we focused our attention on ultra-compact radiation-hard EM calorimeters based on modular structures (RADiCAL modules) consisting of alternating layers of the very dense absorber and scintillating plates, read out via radiation hard wavelength shifting (WLS) solid fiber or capillary elements to photosensors positioned either proximately or remotely, depending upon their radiation tolerance. RADiCAL modules provide the capability to measure simultaneously and with high precision the position, energy and timing of EM showers. This paper provides an overview of the instrumentation and photosensor R&D associated with the RADiCAL program.

Long-term X-ray variability of the symbiotic system RT Cru based on Chandra spectroscopy

ABSTRACT RT Cru belongs to the rare class of hard X-ray emitting symbiotics, whose origin is not yet fully understood. In this work, we have conducted a detailed spectroscopic analysis of X-ray emission from RT Cru based on observations taken by the Chandra Observatory using the Low Energy Transmission Grating (LETG) on the High-Resolution Camera Spectrometer (HRC-S) in 2015 and the High Energy Transmission Grating (HETG) on the Advanced CCD Imaging Spectrometer S-array (ACIS-S) in 2005. Our thermal plasma modelling of the time-averaged HRC-S/LETG spectrum suggests a mean temperature of kT ∼ 1.3 keV, whereas kT ∼ 9.6 keV according to the time-averaged ACIS-S/HETG. The soft thermal plasma emission component (∼1.3 keV) found in the HRC-S is heavily obscured by dense materials (>5 × 1023 cm−2). The aperiodic variability seen in its light curves could be due to changes in either absorbing material covering the hard X-ray source or intrinsic emission mechanism in the inner layers of the accretion disc. To understand the variability, we extracted the spectra in the ‘low/hard’ and ‘high/soft’ spectral states, which indicated higher plasma temperatures in the low/hard states of both the ACIS-S and HRC-S. The source also has a fluorescent iron emission line at 6.4 keV, likely emitted from reflection off an accretion disc or dense absorber, which was twice as bright in the HRC-S epoch compared to the ACIS-S. The soft thermal component identified in the HRC-S might be an indication of a jet that deserves further evaluations using high-resolution imaging observations.

Optimization of Triple Periodic Bilayer Stacks and Aerial Image Performance Analysis

EUV lithography uses 13.5 nm wavelength incident light. For all materials, the absorption of EUV wavelength cannot be neglected. Therefore, EUV lithography system employs a reflective system. In order to to increase the reflectivity rate, We optimize triple periodic bilayer stacks for 13.5 nm EUV- lithography with a 4 × demagnification and an Numerical Aperture (NA) of 0.5. The optimization is performed using multi-objective Genetic Algorithms (GA). Selected bilayer stacks are further investigated by adding a 9.5 nm dense line absorber. The aerial images are calculated and the lithographic performance of these mask designs are evaluated in terms of threshold, NILS, EL and DOF.

Dynamic casting in combination with ramped annealing process for implementation of inverted planar Ag3BiI6 rudorffite solar cells

The use of toxic Pb and insufficient long-term stability continue to limit the commercialization of organic–inorganic hybrid perovskite photovoltaics despite their excellent power conversion efficiencies (PCEs). Inorganic silver bismuth iodide is a strong candidate for a Pb-free and stable light harvester. Using a conventional n-i-p structure with high-temperature-processed TiO2 charge transport layer, PCEs of more than 4% have been achieved. However, development of inverted planar p-i-n architecture supporting low-temperature flexible application are still in its infant stage as the PCE of only 0.02% has been reported. To unravel such poor performance of the p-i-n structure, a Ag3BiI6 rudorffite film has been fabricated using a combination of dynamic casting (DC) and ramped annealing (RA). This technique significantly enhances the surface coverage of Ag3BiI6 on the underlying planar NiOx hole collector. Furthermore, the optimal annealing temperature of 180 °C allows for the formation of a highly polycrystalline and dense absorber. Based on this approach, the unprecedented PCE of 1.08% has been achieved, whereas the conventional method gives the PCE of only 0.07%. The DC/RA method could offer a new perspective for developing Pb-free inorganic rudorffite photovoltaics with an inverted planar architecture.

Probing X-ray emission in different modes of PSR J1023+0038 with a radio pulsar scenario

Transitional pulsars provide us with a unique laboratory to study the physics of accretion onto a magnetic neutron star. PSR J1023+0038 (J1023) is the best studied of this class. We investigate the X-ray spectral properties of J1023 in the framework of a working radio pulsar during the active state. We modelled the X-ray spectra in three modes (low, high, and flare) as well as in quiescence, to constrain the emission mechanism and source parameters. The emission model, formed by an assumed pulsar emission (thermal and magnetospheric) plus a shock component, can account for the data only adding a hot dense absorber covering ∼30% of the emitting source in high mode. The covering fraction is similar in flaring mode, thus excluding total enshrouding, and decreases in the low mode despite large uncertainties. This provides support to the recently advanced idea of a mini-pulsar wind nebula (PWN), where X-ray and optical pulsations arise via synchrotron shock emission in a very close (∼100 km, comparable to a light cylinder), PWN-like region that is associated with this hot absorber. In low mode, this region may expand, pulsations become undetectable, and the covering fraction decreases.

Fabrication of $$\hbox {Cu}_{2}\hbox {ZnSn(S,Se)}_{4}$$ Cu 2 ZnSn(S,Se) 4 thin film solar cell devices based on printable nano-ink

\(\hbox {Cu}_{{2}}\hbox {ZnSnS}_{{4}}\) (CZTS) as a promising light-absorber material has been extensively applied in photovoltaic solar cells due to its huge absorption coefficient (\({\sim }10^{4}\, \hbox {cm}^{-1})\) and optimal bandgap (\({\sim }\hbox {1.5 eV}\)). In this study, stable and printable CZTS nano-ink was acquired by dispersing CZTS nanocrystals (NCs) in organic solutions. The kesterite CZTS NCs possess uniform size and good crystallinity. The Raman peak of CZTS is located at \(330\, \hbox {cm}^{-1}\), which illustrates that the NCs consist of single-phase CZTS without any impurities. The as-prepared CZTS nano-ink was in turn spin-coated onto the Mo substrate to obtain the desired CZTS thin films under the conditions of anti-vacuum. The compact and dense CZTSSe absorbers were acquired by sulphuring and selenizing the as-prepared thin films. The band gap of the photovoltaic absorber materials is 1.2 eV after incorporating Se into the photovoltaic thin films. Finally, the CZTSSe photovoltaic thin film device, whose power conversion efficiency was \(1.40\pm 0.14\%\), was prepared by this easy and green method.

IslandFAST: A Semi-numerical Tool for Simulating the Late Epoch of Reionization

Abstract We present the algorithm and main results of our semi-numerical simulation, islandFAST, which was developed from 21cmFAST and designed for the late stage of reionization. The islandFAST simulation predicts the evolution and size distribution of the large-scale underdense neutral regions (neutral islands), and we find that the late Epoch of Reionization proceeds very fast, showing a characteristic scale of the neutral islands at each redshift. Using islandFAST, we compare the impact of two types of absorption systems, i.e., the large-scale underdense neutral islands versus small-scale overdense absorbers, in regulating the reionization process. The neutral islands dominate the morphology of the ionization field, while the small-scale absorbers dominate the mean-free path of ionizing photons, and also delay and prolong the reionization process. With our semi-numerical simulation, the evolution of the ionizing background can be derived self-consistently given a model for the small absorbers. The hydrogen ionization rate of the ionizing background is reduced by an order of magnitude in the presence of dense absorbers.

Fabrication of dense CIGS film by mixing two types of nanoparticles for solar cell application

Solution method fabrication of copper indium gallium selenide (CIGS) solar cells has attracted researchers due to easy fabrication and cost effective potential. Despite the encouraging results, the process of fabrication of solution processed solar cell faces challenges like use of toxic chemicals, high temperature processing to achieve large grain and dense CIGS absorber film for highly efficient device. Even though many methods have been developed, the voids generated in the CIGS absorber film after high temperature processing adversely affect the performance of fabricated CIGS solar cell to reach its maximum efficiency up to 20% which has already been achieved for vacuum deposited CIGS absorber film. A dense CIGS absorber film can be deposited by tailoring the size of nanoparticles in the ink solution. In this work, two types of nanoparticles, one having 200–500 nm size nanopowder prepared by ball-milling and other with 20–30 nm nanoparticles prepared using chemical solution route are mixed to prepare ink solution and deposited on the substrate to achieve dense and voids free absorber CIGS film . The smaller CIGS nanoparticles were found to occupy voids generated among the bigger CIGS nanopowder under low temperature sintering process. The performance of fabricated solar cells was found to improve when the concentration of smaller nanoparticles increases in the mixture. Solar cell fabricated with CIGS absorber layer deposited using mixture of nanoparticles exhibited 2.1% efficiency whereas only bigger nanopowder absorber film hardly exhibited any photovoltaic response under sintering at 250°C in ambient atmosphere.

Electrodeposition and selenization of brass/tin/germanium multilayers for Cu2Zn(Sn1-xGex)Se4 thin film photovoltaic devices

Dense, closed, homogeneous brass/tin/germanium multilayers have been prepared by electrochemical methods. The stacks were electrodeposited on molybdenum-sputtered soda-lime glass. Brass was deposited first from an aqueous pyrophosphate electrolyte. Then, tin was deposited from a tin(II) pyrophosphate electrolyte. Germanium was deposited as the top film from 5 vol% GeCl4 in propylene glycol. The composition of the brass/tin/germanium stack could easily be controlled by adjustment of the charge of the deposition of each coating and with special attention to exchange reactions. The variation in film thickness was minimized by using a rotating disk electrode (RDE) sample holder with a current thief. Soft-annealing under a nitrogen atmosphere and selenization with elemental selenium resulted in dense, closed copper-poor and zinc-rich CZTGSe absorber material. P-type conductivity was confirmed by photoelectrochemistry and a first photovoltaic device showed a power conversion efficiency of 0.6% and a band gap near 1.2eV (with Ge/(Sn+Ge)=0.38).

A general water-based precursor solution approach to deposit earth abundant Cu2ZnSn(S,Se)4 thin film solar cells

Earth abundant Cu2ZnSn(S,Se)4 (CZTSSe) has been considered as one of the most promising thin film solar cell absorber candidates. Here, we develop a facile water-based precursor solution approach for depositing high-efficiency Cu2ZnSn(S,Se)4 thin film solar cells. In this environmentally friendly approach, inexpensive elemental Cu, Zn, Sn and S powders are used as the starting materials and are dissolved in the aqueous solution of thioglycolic acid and methylamine, forming a homogeneous precursor solution for depositing Cu2ZnSnS4 nanocrystal thin film. As-deposited CZTS nanocrystal thin films are selenized to form the large-grain CZTSSe absorber layers. It was found that Na doping plays an important role in the formation of the extremely dense and flat CZTSSe absorber layer, and fill factor can be significantly improved for Na-doped CZTSSe solar cells, which lead to a photoelectric conversion efficiency of 6.96% with an open-circuit voltage of 378 mV, a short current density of 28.17 mA cm−2, and a fill factor of 65.4%.

Impact of Mo barrier layer on the formation of MoSe2 in Cu(In,Ga)Se2 solar cells

In this study, we investigated the impact of a Mo barrier layer (Mob) on the formation of MoSe2, as it relates to the performance of Cu(In,Ga)Se2 (CIGS) thin film solar cells with a structure of glass/Mo/Mob/CIGS/CdS/i-ZnO/ZnO:Al/Al. Experiments show that an increase in the thickness of Mob led to a significant decrease in the thickness of MoSe2 as well as a slight reduction in the thickness of the CIGS absorber layer following selenization. This can be attributed to the fact that the Na content in the CIGS absorber increased with an increase in the thickness of the Mob. Higher Na content in the absorber layer promoted the formation of Na2Sex at grain boundaries during selenization, thereby reducing the grain boundary diffusion of Se, which retarded the growth of excess MoSe2. Furthermore, the crystallinity of the absorber layer was improved when specific quantities of Na were included, which resulted in a relatively dense absorber layer of reduced thickness. Increasing the thickness of Mob also led to a more homogeneous distribution of elemental Ga throughout the absorber layer. Under optimal conditions (i.e., Mob = 20 nm), the thickness of MoSe2 was reduced from 819 nm to 220 nm, and device efficiency was increased from 4.9% to 10.03%.

Spark plasma sintering of Cu2SnS3 powders synthesized by mechanical alloying

Earth-abundant and nontoxic absorber materials have been extensively studied for thin-film solar cells. One of the most viable candidate materials for solar absorber applications is Cu2SnS3 (CTS). The feasibility of producing fully dense CTS materials by combining mechanical alloying (MA) and spark plasma sintering (SPS) is reported for the first time. X-ray diffraction analysis revealed the formation of the CTS compound, with a monoclinic structure, after 2h of MA. SPS consolidation of the CTS powder particles was performed at 600°C yielding high densification without much sulfur loss or oxidation. Optical band gaps ranging from 1.34eV to 1.11eV were estimated with diffuse reflectance measurements. The approach used constitutes a simple and economic alternative to conventional sintering techniques already used to prepare thin-films from nanopowders and, in the near future, it is believed that SPS will be able to produce dense absorber layers of CTS for thin-film solar cells.

Effect of Binder Content in Cu–In–Se Precursor Ink on the Physical and Electrical Properties of Printed CuInSe2 Solar Cells

Printed chalcopyrite thin films have attracted considerable attention in recent years due to their potential in the high-throughput production of photovoltaic devices. To improve the homogeneity of printed CuInSe2 (CISe) layers, chemical additives such as binder can be added to the precursor ink. In this contribution, we investigate the influence of the dicyandiamide (DCDA) content, used as a binder in the precursor ink, on the physical and electrical properties of printed CISe solar cells. It is shown that the use of the binder leads to a dense absorber, composed of large CISe grains close to the surface, while the bulk of the layer consists of CISe crystallites embedded in a CuxS particle based matrix, resulting from the limited sintering of the precursor in this region. The expected additional carbon contamination of the CISe layer due to the addition of the binder appears to be limited, and the optical properties of the CISe layer are similar to the reference sample without additive. The electrical ch...

A promising sputtering route for dense Cu2ZnSnS4 absorber films and their photovoltaic performance

Copper zinc tin sulfide (Cu2ZnSnS4, CZTS) is highly abundant in nature. It is an important absorber material for the development of low-cost and sustainable next-generation I2–II–IV–VI4 thin-film solar cells because it has a the tunable direct band gap energy, inexpensive constituent elements, and a large absorption coefficient in the visible wavelength region. This work develops an efficient one-step vacuum-based approach to depositing CZTS films without the need to supply excess sulfur during/after deposition or to perform any post-sulfurization treatment. This one-step RF sputtering process produces CZTS films that are crystalline, phase-pure, dense, smooth, and continuous. Air Mass 1.5 G power conversion efficiencies of as high as 6% have been achieved with an antireflection coating, demonstrating that this new approach has great potential as a low-cost alternative for high-efficiency CZTS solar cell production.

9.0% efficient Cu2ZnSn(S,Se)4 solar cells from selenized nanoparticle inks

AbstractThin‐film solar cells using Cu2ZnSn(S,Se)4 absorber materials continue to attract increasing attention. The synthesis of kesterite Cu2ZnSnS4 nanoparticles by a modified method of hot injection is explained. Characterization of the nanoparticles by energy dispersive X‐ray spectroscopy, X‐ray diffraction, Raman, and transmission electron microscopy is presented and discussed. When suspended in an ink, coated, and processed into a device, the nanoparticles obtained by this synthesis achieve a total area (active area) efficiency of 9.0% (9.8%) using AM 1.5 illumination and light soaking. This improvement over the previous efficiency of 7.2% is attributed to the modified synthesis approach, as well as fine‐tuned conditions for selenizing the coated nanoparticles into a dense absorber layer. Copyright © 2014 John Wiley & Sons, Ltd.