Intrinsic Absorber Research Articles

Resonant cavity structural design of carbon-based intrinsic metamaterial absorbers for broadening the effective absorption bandwidth

The effective absorption bandwidth (EAB) of absorptive materials has always been a bottleneck limiting their applications. Particularly, the combination of macroscopic structural design and the loss functions at the microscopic level of materials provides an efficient solution to this issue. Herein, a novel approach was proposed, integrating macroscopic structural design with microscopic loss functions to broaden the effective absorption bandwidth (EAB) through designing an intrinsic metamaterial absorber composed of a uniform blend of carbon-based absorbing materials and polydimethylsiloxane. A key innovation lies in the dual cubic resonant cavity design, where the multiple dimensions of the resonant cavities enable the absorber to achieve effective impedance matching across a wide frequency range. Additionally, the generation of a bottom ring current induces a magnetic field, which enhances the metamaterial absorber’s capability for further attenuation of electromagnetic wave energy. These innovative designs enable traditional carbon-based absorbing materials to achieve exceptional absorption performance, with the EAB being 2.37 times that of the skin structure, addressing the narrow EAB issue of traditional carbon-based absorptive materials. Experimental results demonstrate that the prepared samples achieve an absorption rate of 90 % for electromagnetic waves in the frequency range of 5.74 to 18 GHz under normal incidence, consistent with the simulation results. This absorber boasts advantages of broadband, with an equivalent thickness of only 2.94 mm. Its structure is easy to manufacture, demonstrating certain potential applications, and providing valuable insights for the work of other researchers.

Insight into the Dependence of Photovoltaic Performance on Interfacial Energy Alignment in Solar Cells with Mobile Ions

A key aspect in the optimization of perovskite (PVK) solar cells is the mitigation of interface losses, which are determined by energy band offsets and recombination. Counterintuitively, recent experimental evidence on inorganic PVK solar cells shows that increasing band offsets may improve open‐circuit voltage at efficiency levels over 20%. In order to improve the knowledge of the impact of interfaces, the authors model solar cells consisting of an intrinsic absorber material containing mobile ions, sandwiched between two wide‐gap charge transport layers. The results show that minimizing band offsets decreases interface losses in various scenarios, but cannot be adopted as a universal optimization rule. For instance, even in the absence of interface recombination, unequal majority carrier band offsets avoid high injection conditions. Moreover, assuming a fixed band offset at one interface, the band offset at the opposite interface should be reduced if it shows the highest interface recombination, or increased if it shows the lowest recombination. Remarkably, it is found that solar cells with mobile ions hold the potential to outperform of ion‐free counterparts, depending on the extent to which the interplay between band offsets and Debye layers result in the establishment of a majority carrier concentration in the intrinsic absorber.

A Broadband X-Ray Study of the Dwarf Nova SS Cyg during Quiescence and Outburst

We present a broadband X-ray study (∼0.3–50 keV) of the dwarf nova SS Cyg highlighting the changes in the accretion during two phases, the quiescence and the outburst states. The investigation was based on simultaneous observations carried out with the XMM-Newton and NuSTAR telescopes in two epochs, involving medium- and high-resolution spectroscopy. Spectra were harder during quiescence (kT high ∼ 22.8 keV) than the outburst (kT high ∼ 8.4 keV), while the mass accretion rate increased by ∼35 times in the outburst (1.7 × 1016 g s−1) as compared to quiescence. The bolometric luminosity (0.01–100.0 keV) during the outburst was dominated by a blackbody emission (kT BB ∼ 28 eV) from the optically thick boundary layer (BL), and the inner edge of the accretion disk resides very close to the white-dwarf (WD) surface. X-rays from the BL are consistent with the WD having mass . Our study conclusively confirms the presence of the reflection hump in the 10–30 keV range for both phases, which arises when X-ray photons hit colder material and undergo Compton scattering. We estimated a similarly strong reflection amplitude during quiescence (∼1.25) and the outburst (∼1.31), indicating both the WD surface and disk are contributing to reflection. The neutral Fe K α line, which is correlated with Compton reflection, also showed similar strength (∼80 eV) in both phases. Finally, X-rays also revealed the presence of a partial intrinsic absorber during the outburst, possibly due to an outflowing accretion disk wind.

Low-ionization iron-rich broad absorption-line quasar SDSS J 1652+2650: physical conditions in the ejected gas from excited Fe ii and metastable He i

ABSTRACT We present high-resolution VLT/UVES spectroscopy and a detailed analysis of the unique broad absorption-line system towards the quasar SDSS J 165252.67+265001.96. This system exhibits low-ionization metal absorption lines from the ground states and excited energy levels of Fe ii and Mn ii, and the meta-stable $2\, ^3S$ excited state of He i. The extended kinematics of the absorber encompasses three main clumps with velocity offsets of −5680, −4550, and −1770 km s−1 from the quasar emission redshift, z = 0.3509 ± 0.0003, derived from [O ii] emission. Each clump shows moderate partial covering of the background continuum source, Cf ≈ [0.53; 0.24; 0.81]. We discuss the excitation mechanisms at play in the gas, which we use to constrain the distance of the clouds from the active galactic nucleus (AGN) as well as the density, temperature, and typical sizes of the clouds. The number density is found to be nH ∼ 104 cm−3 and the temperature Te ∼ 104 K, with longitudinal cloudlet sizes of ≳0.01 pc. cloudy photoionization modelling of He i⋆, which is also produced at the interface between the neutral and ionized phases, assuming the number densities derived from Fe ii, constrains the ionization parameter to be log U ∼ −3. This corresponds to distances of a few 100 pc from the AGN. We discuss these results in the more general context of associated absorption-line systems and propose a connection between FeLoBALs and the recently identified molecular-rich intrinsic absorbers. Studies of significant samples of FeLoBALs, even though rare per se, will soon be possible due to large dedicated surveys paired with high-resolution spectroscopic follow-ups.

The extremely X-ray luminous radio-loud quasar CFHQS J142952 + 544717 at z = 6.18 under Chandra high-angular resolution lens

ABSTRACT We present the first X-ray observation at sub-arcsecond resolution of the high-redshift (z = 6.18) radio-loud quasar CFHQS J142952 + 544717 (J1429). The ∼100 net-count 0.3–7 keV spectrum obtained from ∼30 ks Chandra exposure is best fit by a single power-law model with a photon index Γ = 2.0 ± 0.2 and no indication of an intrinsic absorber, implying a 3.6–72 keV rest-frame luminosity $L_{\rm X}=(2.3^{+0.6}_{-0.5})\times 10^{46}$ erg s−1. We identify a second X-ray source at 30″ distance from J1429 position, with a soft (Γ ≃ 2.8) and absorbed (equivalent hydrogen column density NH < 13.4 × 1020 cm−2) spectrum, which likely contaminated J1429 spectra obtained in lower angular resolution observations. Based on the analysis of the Chandra image, the bulk of the X-ray luminosity is produced within the central ∼3 kpc region, either by the disc/corona system, or by a moderately aligned jet. In this context, we discuss the source properties in comparison with samples of low- and high-redshift quasars. We find indication of a possible excess of counts over the expectations for a point-like source in a 0.5″–1.5″ (∼3−8 kpc) annular region. The corresponding X-ray luminosity at J1429 redshift is 4 × 1045 erg s−1. If confirmed, this emission could be related to either a large-scale X-ray jet, or a separate X-ray source.

Straddling type sandwiched absorber based solar cell structure

We have proposed a solar cell structure that could utilize sub-bandgap photons along with the usual above bandgap energy photons. This device configuration could achieve efficiency beyond the single bandgap solar cell limit of 33 %. A low bandgap intrinsic absorber is embedded into a high bandgap intrinsic absorber making a straddling type sandwiched configuration. Stradling type alignment and conduction band offset make a confinement region in the sandwich absorber region. This configuration is put into a p+ and n+ for providing an internal electric field. The various aspect of confinement region carrier transport, and its physical parameters controlling device performance such as thickness, position, and barrier height, are investigated. The device working in terms of recombination and net power generation is optimized. The optimal efficiency of such a structure is observed to be 43 % with high VOC and JSC values.

Study of Complex Absorption and Reflection in a Unique Intermediate Polar Paloma

We present the broadband (0.3–40.0 keV) X-ray analysis of a unique intermediate polar Paloma using simultaneous data from XMM-Newton and NuSTAR observatories. The X-ray power spectra show strong modulations over orbital period compared to spin period. The orbit-folded light curves show a single broad hump-like structure with strong dips for soft to medium X-rays (0.3–10.0 keV). The energy-dependent dips at ϕ ∼ 0.16 and 0.5 arise as a result of a complex intrinsic absorber, strong enough to have an effect around 15 keV. The absorber could potentially be contributed from accretion curtain/accretion stream and absorbing material produced by stream–disk/stream–magnetosphere interactions. We notice significant variation of the absorber with orbital phase, with maximum absorption during orbital phase 0.1–0.22. The absorber requires more than one partial covering absorber component, specifying the necessity to use distribution of column densities for spectral modeling of the source. The isobaric cooling flow component is utilized to model the emission from the multitemperature post-shock region, giving a shock temperature of keV, which corresponds to a white dwarf mass of . We have used both the neutral absorber and warm absorber models, which statistically give a similarly good fit, but with different physical implications. Among the Fe Kα line complex, the neutral line is the weakest. We probed the Compton reflection and found a minimal statistical contribution in the spectral fitting, suggesting the presence of weak reflection in Paloma.

Stability and degradation in triple cation and methyl ammonium lead iodide perovskite solar cells mediated via Au and Ag electrodes

Perovskite solar cells (PSCs), particularly based on the methyl ammonium lead iodide (MAPbI3) formulation, have been of intense interest for the past decade within the photovoltaics (PV) community, given the stupendous rise in power conversion efficiencies (PCEs) attributed to these perovskite formulations, where PCEs have exceeded 25%. However, their long-term stability under operational conditions and environmental storage are still prime challenges to be overcome towards their commercialization. Although studies on the intrinsic perovskite absorber stability have been conducted previously, there are no clear mechanisms for the interaction of electrode-induced absorber degradation pathways, which is the focus of this study. In this report, we have conducted a comprehensive analysis on the impact of the electrode collector layer, specifically Ag and Au, on the degradation mechanism associated with the MAPbI3 and a triple cation absorber, Cs0.05FA0.79MA0.16PbI2.45Br0.55. Notably, Au-based PSCs for both absorbers in an n-i-p architecture showed superior PCE over Ag-based PSCs, where the optimized PCE of MAPbI3 and triple cation-based PSCs was 15.39% and 18.21%, respectively. On the other hand, optimized PCE of MAPbI3 and triple cation-based PSCs with Ag electrodes was 3.02% and 16.44%, respectively. In addition, the Ag-based PSCs showed a rapid decrease in PCE over Au-based PSCs through operational stability measurements. We hypothesize the mechanism of degradation, arising from the Ag interaction with the absorber through the formation of AgI in the PSCs, leads to corrosion of the perovskite absorber, as opposed to the benign AuI when Au electrodes are used in the solar cell stack. Additionally, novel use of photoluminescence spectroscopy (PL) here, allowed us to access key features of the perovskite absorber in situ, while it was in contact with the various layers within the n-i-p solar cell stack. A quenching in the PL peak in the case of Ag-contacted MAPbI3 provided direct evidence of the Ag corrupting the optical properties of the absorber through the formation of AgI which our X-ray diffraction (XRD) results confirmed. This was supported by the fact that an emission peak was still present in the triple cation Ag-device. For the Au-contacted MAPbI3 the presence of a well-defined PL peak, though attenuated from the triple cation Au-device, suggested the AuI does not quell the emission spectrum for either the triple cation or the MAPbI3 absorber. The findings should aid in the understanding and design of new electrode materials with PSCs, which will help accelerate their introduction into the commercial sector in the future.

Recent trends and challenges in developing boride and carbide-based solar absorbers for concentrated solar power

Concentrating solar power technology has gained increased attention as a source for clean energy. However, because of low power density, it requires large areas and materials with high photothermal conversion efficiency, to harness solar energy. The solar receiver coated with solar selective material plays a critical role in efficiently converting solar energy to useful power. Because of the moderate solar selective nature and excellent thermal properties, significant efforts are currently being invested on the use of ultra-high temperature ceramics as solar selective absorbers. This literature survey presents a critical review of the research and development of early transition metal boride and carbide-based solar selective absorbers, both in bulk and tandem coating formats. In particular, we have emphasized the use of transition metal borides and carbides as intrinsic absorbers as bulk or even exploiting a multilayer design approach to improve the absorptance in the solar spectrum region. One of the key aspects is to introduce a gradient in optical constants (refractive index, extinction coefficient) to tailor high absorptance and low emissivity in tandem absorber coatings, with insightful understanding into microstructure-optical property correlation. The challenges in developing tandem solar absorbers with long-term thermal stability at mid to high temperature window in different working atmosphere are emphasized to spur the development of next generation spectrally-selective solar absorbers.

State of the Art in Carbon Nanomaterials for Photoacoustic Imaging.

Photoacoustic imaging using energy conversion from light to ultrasound waves has been developed as a powerful tool to investigate in vivo phenomena due to their complex characteristics. In photoacoustic imaging, endogenous chromophores such as oxygenated hemoglobin, deoxygenated hemoglobin, melanin, and lipid provide useful biomedical information at the molecular level. However, these intrinsic absorbers show strong absorbance only in visible or infrared optical windows and have limited light transmission, making them difficult to apply for clinical translation. Therefore, the development of novel exogenous contrast agents capable of increasing imaging depth while ensuring strong light absorption is required. We report here the application of carbon nanomaterials that exhibit unique physical, mechanical, and electrochemical properties as imaging probes in photoacoustic imaging. Classified into specific structures, carbon nanomaterials are synthesized with different substances according to the imaging purposes to modulate the absorption spectra and highly enhance photoacoustic signals. In addition, functional drugs can be loaded into the carbon nanomaterials composite, and effective in vivo monitoring and photothermal therapy can be performed with cell-specific targeting. Diverse applied cases suggest the high potential of carbon nanomaterial-based photoacoustic imaging in in vivo monitoring for clinical research.

Understanding the Origin of Thermal Annealing Effects in Low‐Temperature Amorphous Silicon Films and Solar Cells

A detailed investigation of the effects of prolonged postdeposition annealing on the performance of amorphous silicon (a‐Si:H) solar cells and the properties of individual a‐Si:H layers that are fabricated at low temperature of 120 °C is presented. A substantial improvement in all parameters of the current–voltage curves of these solar cells is observed upon annealing, consistent with an improvement in the collection voltage of the solar cells. Modifications of p‐type layers during deposition of the solar cells are found to make no significant contribution to the annealing behavior of solar cells, while variations in the properties of n‐type and intrinsic layers contribute substantially. The results indicate that the largest contribution to the annealing effect originates from changes in the electronμτ‐product in the intrinsic absorber layer upon annealing, while changes in holeμτ‐products have a minor contribution to the annealing effect in the solar cell. Besides a lack of significant changes in the number of recombination centers upon annealing, an improvement in the external quantum efficiency curves upon annealing may be accurately reproduced in computer simulations by assuming an increase in the band mobilities of both electrons and holes.

A broad-band X-ray study of the asynchronous polar CD Ind

ABSTRACT We present a simultaneous broad-band analysis of X-ray data obtained with the XMM–Newton and the Nuclear Spectroscopic Telescope Array (NuSTAR) for the asynchronous polar source, CD Ind. The spin-folded light curve in the soft 0.3–3.0 keV band shows a single broad hump-like structure superimposed with occasional narrow dips, indicating a single-pole accretion model with a complex intrinsic absorber. Lack of strong modulation in the folded light curve above 3 keV reveals that emission from the corresponding zone of the post-shock region (PSR) remains in view throughout the spin phase. The broad-band spectrum is modelled with a three-component absorbed plasma emission model and absorbed isobaric cooling flow model, both of which fit the data well with similar statistical significance. The presence of a partial covering absorber is evident in the spectra with equivalent column density ${\sim}7\times 10^{22}\, \text{cm}^{-2}$ and a covering fraction of ~25 per cent. Strong ionized oxygen Kα line emission is detected in the spectra. We notice spectral variability during the spin phase 0.75–1.05, when there is a considerable increase in the column density of the overall absorber (from ${\sim}1 \times 10^{20}\, \text{cm}^{-2}$ to ${\sim}9 \times 10^{20}\, \text{cm}^{-2}$). We required at least three plasma temperatures to describe the multitemperature nature of the PSR. The shock temperature ${\sim}43.3_{-3.4}^{+3.8}$ keV, represented by the upper temperature of the cooling flow model, implies a white dwarf mass of ${\sim}0.87^{+0.04}_{-0.03}\, \mathrm{M}_{\odot }$. The iron Kα line complex show strong He-like and weak neutral fluorescence lines. We could not unambiguously detect the presence of Compton reflection in the spectra, which is probably very small and signifies a tall shock height.

Impact of Band-gap Graded Intrinsic Layer on Single-junction Band-gap Tailored Solar Cells

Objective: The work investigates the performance of intrinsic layers with and without band-gap tailoring in single-junction amorphous silicon-based photovoltaic cells. The work proposes single-junction amorphous silicon solar cells in which band-gap grading has been done between layers as well as within each layer for the first time. Materials & Methods: The samples of hydrogenated amorphous silicon-germanium with different mole fractions are fabricated, and their band-gaps are validated through optical characterization and material characterization. A single-junction solar cell with an intrinsic layer made up of hydrogenated amorphous silicon (aSi:H) having a band-gap of 1.6 eV is replaced by continuously graded hydrogenated amorphous silicon-germanium (aSi1-xGe x H) intrinsic bottom layers having bandgaps ranging from 0.9 eV to 1.5 eV. The proposed structure has been considered as a variant of previously designed single-junction band-gap tailored structures. Results: The suitable utilization of band-gap tailoring on the intrinsic absorber layer aids more incident photons in energy conversion and thereby attain a better short circuit current density of 19.89 mA/cm2.

Improved Efficiency of Perovskite Solar Cells with Low‐Temperature‐Processed Carbon by Introduction of a Doping‐Free Polymeric Hole Conductor

Low‐temperature‐processed carbon‐based perovskite solar cells (C‐PSCs) are promising photovoltaic devices, because of their good stability, low cost, and simple preparation methods, which allow for scalable processing. Herein, C‐PSCs with the n−i−p structure are prepared, using a SnO2 nanoparticles film as the electron‐selective contact, MAPbI3 perovskite as the intrinsic absorber layer (MA = methylammonium), and a carbon layer as the hole‐selective layer and conductor. Carbon is, however, not an ideal hole‐selective layer and it is found that improved solar cell performance can be obtained by introducing a polymeric hole conductor between the perovskite and the carbon layer. Specifically, undoped poly(3‐hexylthiophene) (P3HT) is used for this purpose, as it is stable and highly hydrophobic. For ITO/SnO2/MAPbI3/carbon devices, a solar cell efficiency of up to 12.8% is obtained, increasing up to 15.7% with the inclusion of a P3HT layer, which increases open‐circuit potential, photocurrent, and fill factor (FF). In comparison, ITO/SnO2/MAPbI3/P3HT/Au devices performed rather poorly (up to 11.7%). Encouraging stability is obtained for unencapsulated C‐PSC devices: P3HT/carbon devices do not show any degradation in solar cell performance upon storage for 1 month in low humidity, while they maintain 70% of their initial efficiency after 900 h at 82 °C in air.

Elucidating Mechanistic Details of Photo-Induced Charge Transfer in Antimony Sulfide-Based p-i-n Junctions

The initial kinetics and mechanisms of photo-induced charge transfer in photovoltaic materials are critical to the operation of fabricated devices. Despite the importance of charge transfer in the picosecond to nanosecond timescales, mechanistic understanding of these events is still limited. To address this challenge, a series of p-i-n junction samples that comprises fluorine-doped tin oxide (FTO)/TiO2/ZnS/Sb2S3/P3HT layers was prepared by atomic layer deposition (ALD). ALD allows for carefully controlled film thickness in samples that enable systematic evaluation of photo-induced charge-transfer kinetics by transient absorption spectroscopy (TAS). Sb2S3 serves as the intrinsic light absorber, P3HT is the hole acceptor, and TiO2 is the electron acceptor. An extremely thin, electron-blocking layer of ZnS was deposited between Sb2S3 and TiO2 varied in thickness by ALD to create a series of 20 samples that included (1) five different ZnS thicknesses (0, 2, 5, 10, and 15 ALD cycles) and (2) four combinations of layers, always including ZnS/Sb2S3, that built up to the completed stack. These mechanistic studies confirm our proposed mechanism for photo-induced electron and hole transfer and recombination in these p-i-n junction samples and provide predictive insights into the charge-transfer processes that may be most determinant in the operation of completed devices.

Double-layer solar absorber coating based on high entropy ceramic AlCrMoTaTiN: Structure, optical properties and failure mechanism

With the rapid advance of science and technology, it is essential to research and develop new intrinsic solar absorber coatings with the simple production process and excellent photo-thermal conversion efficiency. Herein, we have developed a novel AlCrMoTaTiN intrinsic absorber layer by radio frequency (RF) reactive sputtering method via adjusting the deposition time and the flow rate of N2. The AlCrMoTaTiN intrinsic absorber layer exhibits a high absorptance of 0.752 and a low emittance of 0.074 at 82 °C. The AlCrMoTaTiN/Al2O3 solar absorber coating is deposited by using Al2O3 works as an anti-reflective layer and the spectral selectivity (α/ε) is 0.929/0.082. This coating also possesses a good thermal stability, which can be stabilized at 300 °C in air and 500 °C in vacuum for 2 h, respectively. In addition, a prolonged period of thermal stability characterization is carried out, which indicates that this coating could keep good optical performance after annealing at 600 °C for 100 h. The corresponding failure mechanism is obtained by analyzing the Raman spectroscopy and XRD. Obviously, the AlCrMoTaTiN/Al2O3 solar absorber coating has a broad application prospect in large-scale and efficient industrial production.

Sprayable PEDOT:PSS based spectrally selective coating for solar energy harvesting

A novel spectrally selective coating was developed on stainless substrates using commercially available poly(ethylene-3,4-dioxythiophene):poly (styrene sulfonate), (PEDOT:PSS) polymer for solar energy harvesting applications. An intrinsic (i.e., single) absorber layer concept was used to develop this coating. The as-prepared PEDOT:PSS dispersion was applied on substrates with thickness in the range of 0.1–5.8 μm using an automated spray deposition system, and the effect of thickness on the optical properties was studied in detail. The intrinsic properties of PEDOT:PSS resulted in high absorptance and low emittance, this was ascertained using glass, quartz and KBR pellets. With optimization of coating thickness, the reflectance edge shifted towards higher wavelength and near perfect absorption was obtained over a broad wavelength range leading to very high absorptance. The optimized PEDOT:PSS coating (approximately 5.8 μm thick) deposited on stainless steel substrates exhibited absorptance of 0.967 and emittance of 0.36.

Search for intrinsic NALs in BAL/mini-BAL quasar spectra

ABSTRACT Some fraction of narrow absorption lines (NALs) are physically associated to the quasar/host-galaxy materials (i.e. intrinsic NALs) like those of broad absorption lines (BALs) and mini-BALs. The relation between these three types of absorption lines has not been understood yet, however one interpretation is that these absorption features correspond to different inclination angles. In this study, we search for intrinsic NALs in 11 BAL/mini-BAL quasar spectra retrieved from VLT/UVES public archive, in order to test a possible relation of intrinsic NALs and BALs/mini-BALs in the geometry models. We use partial coverage analysis to separate intrinsic NALs from ones which are associated to cosmologically intervening materials like foreground galaxies and intergalactic medium (i.e. intervening NALs). We identify one reliable and two possible intrinsic NAL systems out of 36 NAL systems in 9 BAL/mini-BAL quasar spectra after removing two quasars without clear BAL features. In spite of a small sample size, we placed a lower limit on the fraction of BAL/mini-BAL quasars that have at least one intrinsic C iv NAL ($\sim 33^{+33}_{-18}{{\ \rm per\ cent}}$). This can be interpreted that intrinsic NAL absorbers exist everywhere regardless of inclination angle. We found that one of the intrinsic NAL systems detected in SDSS J121549.80−003432.1 is located at a large radial distance of R > 130 kpc, using a method of photoionization model with ground/excited-state lines. Considering the wide range of intrinsic NAL absorber distribution in inclination angles and radial distances, it suggests that origins and geometry of them are more complicated than we expected.

Milky-Way-Like 2175 Å Dust Extinction Feature Observed toward the Quasar SDSS J0916[formula omitted]2921

Spectral observations indicated that the quasar SDSS J091613.60+ 292106.1 (simply called as J0916+2921, with the system redshift of zem=1.1418±0.0018) has a Milky-Way-like 2715Å dust extinction feature, its strength is obviously greater than the average value of the Galaxy. At the same time, a plenty of gas absorption lines in association with dust were detected, their system redshift is determined to be zabs=1.1413±0.0002, in consistence with the quasar redshift. The ratios of column densities of gaseous metal ions relative to the Solar metallicity are [Al/Zn]=−1.68±0.10, [Cr/Zn]=−0.49±0.10, and [Fe/Zn]=−0.81±0.18. The significant effect of dust dissipation indicates that the absorber is heavily dusty, supporting the detection of the 2175Å dust extinction feature. The Milky-Way-like dust extinction was usually observed in the intervening quasar absorbers, but its existence in the quasar intrinsic absorber has never been confirmed before. The associated dust absorber toward the quasar SDSS J0916+2921 is one of the several intrinsic 2175Å absorber candidates. The X-ray radiation of the quasar is greater than the average value. This may provide a natural laboratory for further studying the equilibrium of formation and dissociation of 2175Å dust grains under the irradiation of strong high-energy radiations, so that their chemical composition, physical structure, and origin can be revealed.

Spectral absorption control of femtosecond laser-treated metals and application in solar-thermal devices

Direct femtosecond (fs) laser processing is a maskless fabrication technique that can effectively modify the optical, electrical, mechanical, and tribological properties of materials for a wide range of potential applications. However, the eventual implementation of fs-laser-treated surfaces in actual devices remains challenging because it is difficult to precisely control the surface properties. Previous studies of the morphological control of fs-laser-processed surfaces mostly focused on enhancing the uniformity of periodic microstructures. Here, guided by the plasmon hybridisation model, we control the morphology of surface nanostructures to obtain more control over spectral light absorption. We experimentally demonstrate spectral control of a variety of metals [copper (Cu), aluminium (Al), steel and tungsten (W)], resulting in the creation of broadband light absorbers and selective solar absorbers (SSAs). For the first time, we demonstrate that fs-laser-produced surfaces can be used as high-temperature SSAs. We show that a tungsten selective solar absorber (W-SSA) exhibits excellent performance as a high-temperature solar receiver. When integrated into a solar thermoelectric generation (TEG) device, W-SSA provides a 130% increase in solar TEG efficiency compared to untreated W, which is commonly used as an intrinsic selective light absorber.