Visible Region Research Articles

Enhanced broadband perfect absorption in visible and near-infrared regimes

ABSTRACT It is still a challenge to achieve perfect ((near-unity)) absorption across a wide wavelength range with a three-layer structure. This paper presents a metamaterial absorber (MA) based on MXene that can achieve broadband and perfect absorption in the near-infrared and visible regions. The MA with a simple three-layer structure consists of a top Ti3C2T x layer, an intermediate dielectric layer and a bottom gold layer. It can achieve perfect absorption (the absorptivity over 99%) in the wavelength range of 730–900 nm. The electric field distribution reveals that the localized surface plasmon resonance occurring at the interface of Ti3C2T x and SiO2 leads to strong absorption over the wide wavelength range. Furthermore, the MA exhibits excellent angular stability. This work provides a method to construct MAs with broadband perfect absorption in the near-infrared and visible band.

Nanosized Eu3+-Doped NaY9Si6O26 Oxyapatite Phosphor: A Comprehensive Insight into Its Hydrothermal Synthesis and Structural, Morphological, Electronic, and Optical Properties.

Detailed analysis covered the optical and structural properties of Eu3+-doped NaY9Si6O26 oxyapatite phosphors, which were obtained via hydrothermal synthesis. X-ray diffraction patterns of NaY9Si6O26:xEu3+ (x = 0, 1, 5, 7, 10 mol% Eu3+) samples proved a single-phase hexagonal structure (P63/m (176) space group). Differential thermal analysis showed an exothermic peak at 995 °C attributed to the amorphous to crystalline transformation of NaY9Si6O26. Electron microscopy showed agglomerates composed of round-shaped nanoparticles ~53 nm in size. Room temperature photoluminescent emission spectra consisted of emission bands in the visible spectral region corresponding to 5D0 → 7FJ (J = 0, 1, 2, 3, 4) f-f transitions of Eu3+. Lifetime measurements showed that the Eu3+ concentration had no substantial effect on the rather long 5D0-level lifetime. The Eu3+ energy levels in the structure were determined using room-temperature excitation/emission spectra. Using the 7F1 manifold, the Nv-crystal field strength parameter was calculated to be 1442.65 cm-1. Structural, electronic, and optical properties were calculated to determine the band gap value, density of states, and index of refraction. The calculated direct band gap value was 4.665 eV (local density approximation) and 3.765 eV (general gradient approximation). Finally, the complete Judd-Ofelt analysis performed on all samples confirmed the experimental findings.

Prediction of 2D XC2N4 (X= Ti, Mo, and W) monolayers with high mobility as an encouraging candidate for photovoltaic devices

In this study, the impacts of strain and an electric field on the electronic and optical characteristics of monolayer XC2N4 (X=Ti, Mo, and W) were systematically examined using the density functional theory. The results corroborated that the dynamically, mechanically, and thermodynamically stable XC2N4 monolayers displayed semiconductor properties when the Heyd-Scuseria-Ernzerhof (HSE06) method was used. The TiC2N4 monolayer is shown to be a direct-gap semiconductor of 1.179 eV whereas the MoC2N4 and WC2N4 monolayers are indicated to have indirect bandgaps of 2.819 eV and 2.661 eV, respectively. Notably, the TiC2N4, WC2N4, and MoC2N4 monolayers possess comparatively high electron mobilities of 2776.85 cm2/V s, 1576.79 cm2/V s, and 1316.41 cm2/V s, respectively. The influence of strain on the bandgap of the MoC2N4 and WC2N4 monolayers led to a decrease in their gap, whereas in the TiC2N4 monolayer, the applied tensile strain caused an increase in the bandgap. Moreover, the compressive strain significantly caused a transition from semiconducting to metallic characteristics (zero band gap). The optical absorption spectra indicated the existence of three separate maxima for the XC2N4 (X=Ti, Mo, and W) monolayers with an extreme intensity of up to 2.0 × 105 cm−1. Interestingly, compared with pure monolayers, strained monolayers enhance the beginning of coefficient absorption in the visible range, with widespread range absorption in the ultraviolet and visible regions. Our results suggest that these monolayers can be promising options for nanoelectronic, optical and photovoltaic applications.

A Prediction of All-Inorganic Lead-Free Halide Perovskites for Photovoltaic Application: Rb3Mo2Br9 and Rb3Mo2Cl9.

Lead-based organic-inorganic hybrid perovskites show promise as photovoltaic materials due to their high energy conversion efficiencies. However, concerns regarding lead toxicity and the poor environmental and operational stability of the organic cationic group have limited their widespread application. To address these challenges, the design of all-inorganic lead-free halide perovskites offers potential solutions for photovoltaic applications. Here, two layered perovskite derivatives, Rb3Mo2Cl9 and Rb3Mo2Br9, are explored, and their electronic, structural, and photovoltaic properties are analyzed using advanced theoretical calculations. Rb3Mo2Br9 exhibits a suitable direct bandgap of 1.60eV, making it a promising candidate for use as a light absorber in low-cost, high-efficiency solar cells. On the other hand, Rb3Mo2Cl9 demonstrates a wide direct bandgap exceeding 1.70eV, positioning it as a viable option for use as a top cell in tandem photovoltaic systems alongside silicon. Both materials display ideal optical properties in the visible light region and hold promise as excellent inorganic lead-free perovskite alternatives.

Photothermal performance of carbon nanotubes in the visible and near-infrared regions: applications in water evaporation and destroying cancer cells

Photothermal performance of carbon nanotubes in the visible and near-infrared regions: applications in water evaporation and destroying cancer cells

Synthesis of multifunctional NiFe2O4-Zns-Ag nanocomposite for sunlight driven photocatalytic dye degradation and solar cells applications: Structural, magnetic and optical properties

This article focuses on the fabrication and investigation of the novel multifunctional NiFe2O4-Zns-Ag core-bi-shell nanocomposite and their magnetic optical properties. The nanocomposite was prepared by a simple co-precipitation method and characterized using various techniques such as XRD, SEM, TEM, UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and VSM. The results showed that the nanocomposite had a spinel cubic structure with an average crystallite size of 29 nm. The SEM and TEM images revealed that the nanocomposite had a spherical shape with an average particle size of 61 nm. The optical study demonstrated that the nanocomposite had high absorption in the visible region, indicating its potential for photocatalytic applications. The magnetic study showed that the nanocomposite was superparamagnetic in nature, which could be useful in magnetic separation processes. Furthermore, the potential application of the nanocomposite in solar cells was explored by studying its optical absorption properties. Finally, the photocatalytic activity of the nanocomposite was evaluated using two different azoic dyes under sunlight irradiation. The results showed that the nanocomposite exhibited excellent photocatalytic activity, with a degradation efficiency of 96.22 % within 90 min. Overall, this study provides insights into the potential use of NiFe2O4-Zns-Ag nanocomposite as an efficient photocatalyst for environmental remediation.

Optical investigation of degradation of graphene oxide in alkaline environment: Evidence of two distinct photon-emitting phases in visible region.

In this work we show a procedure of treating of the graphene oxide in alkaline environment as a function of the treatment time in order to obtain novel structures with strong luminescence properties, water-stable, useful as potential replacement for critical raw materials employed as example in optical and optoelectronic devices or for diagnostic and therapeutic technology. These structures have distinct blue and green-luminescence properties which derived most likely from different structural conformations, one associable with that of carbon quantum dots (or as an alternative to that of the Oxidative Debris), the other, lighter and more similar to organic compounds, reported in literature as fulvic-like molecules, but whose nature has to be further investigated. We show that the lighter fraction has a dual mechanism of photoemission: the excitation-independent PL for excitation wavelength within 350 nm and the excitation-dependent component for excitation wavelength ranging in the visible spectrum. The PL dual behaviour could depend on fluorescent nanoclusters composed by specific organic fluorophores with a carbonaceous core. FTIR analysis shows reasonably the same functional groups unless of some difference discussed in the text, meanwhile UV–Vis and PL analysis clearly highlight two distinct emissions (450 nm and 530 nm) in the visible region of the electromagnetic spectrum. Excitation-dependent photoluminescence, water stability and organic fluorescent nanostructures are issues particularly required for application in the biological field but also in materials science.

Optical properties of crystals and two-phase ceramics of the AgCl0.25Br0.75 – AgI system

Research of materials’ optical properties is critical for further development and manufacturing of optical products. While recently, single crystals and two-phase ceramics of the AgCl0.25Br0.75 – AgI system have been developed by the authors. This work is focused on studying the transmission ranges, refractive index dispersion, optical losses, and photoresistance of materials in the AgCl0.25Br0.75 – AgI system, as well as comparing the properties of single-crystals and ceramics. The materials are transparent in the visible and IR regions from 0.49 to 54 um, as well as in the terahertz (far IR and millimeter regions) of 300–1500 um (0.3–1.0 THz). For all compositions, the refractive index in the IR varied from 2.107 to 2.436. The materials’ absorption coefficients were (0.06–6.67) ∙ 10-4 in the middle IR, which is lower compared to other halide materials known and indicates low optical loss. Finally, both single-crystals and two-phase ceramics showed a trend towards an increase in photoresistance with a rise of the AgI content in the AgCl0.25Br0.75 solid solution. After UV irradiation, the materials showed a decrease in transmission in the visible and middle IR (to 10 µm) with negligible loss at a wavelength of 10 µm or more. For a single crystal and two samples of ceramics with a composition of 20 mol. % AgI in AgCl0.25Br0.75, a comparison of properties was conducted in this study. Based on the comparison results, close but not identical values of the refractive indices, an increase in the absorption coefficient for ceramic materials, and a low photoresistance of the sample obtained from the mechanical mixture were revealed. The last two characteristics are associated with the high heterogeneity of two-phase ceramics based on a mechanical mixture, which leads to a deterioration in functional properties. These results prove high prospects for the use of these materials in fiber optics and photonics for medical technologies, thermography, and optoelectronics.

Surface-Reconstructed InAs Colloidal Nanorod Quantum Dots for Efficient Deep-Shortwave Infrared Emission and Photodetection.

Shortwave infrared (SWIR) light emitters and detectors are crucial in numerous applications. Conventionally, SWIR devices rely on epitaxially grown narrow bandgap semiconductors, such as InGaAs, which are expensive to fabricate and difficult to integrate with silicon complementary metal-oxide-semiconductors (CMOS). Colloidal quantum dots (CQDs) have emerged as low-cost alternatives to epitaxially grown semiconductors, offering integration with CMOS through solution-processing methods. However, the predominant SWIR-active CQD systems rely on heavy-metal-containing compositions (PbS and HgTe), hindering the adoption of CQD SWIR technology. InAs CQDs are promising substitutes in SWIR applications. However, synthesizing SWIR-active InAs CQDs is challenging, often constraining them to the visible or near-infrared regions. To achieve SWIR bandgaps, large InAs CQDs are typically required; such CQDs are prone to having surface traps that quench photogenerated charge carriers, adversely affecting device performance. Here, we report a two-step synthesis of surface-passivated SWIR-active InAs/ZnSe core/shell colloidal nanorod quantum dots (CNQDs). These surface-passivated CNQDs are highly emissive and tunable over the entire technologically important region (1200-1800 nm) of the SWIR window with photoluminescence quantum yields as high as 60%. Using these SWIR-active InAs/ZnSe CNQDs, we demonstrated an SWIR-active InAs CQD photodetector, achieving a record high external quantum efficiency of ∼15% at ∼1450 nm and a low dark current of ∼10-2 mA/cm2.

Synthesis and Optical Properties of Organic-Inorganic Hybrid[(18-Crown-6)K][MoOCl4(H2O)

Crown ether anchored organic-inorganic hybrid halides have been recently reported as interesting luminescent materials in the visible region of electromagnetic spectrum. Is it possible to develop such crown ether anchored hybrid materials for near infrared emission? Motivated by this question, we designed a new hybrid material, namely, [(18-Crown-6)K][MoOCl4(H2O)]. 18-Crown-6 ether bound with K+ form the cationic part [(18-Crown-6)K]+. The K+ of [(18-Crown-6)K]+ electrostatically interacts with Cl- of the anionic part [MoOCl4(H2O)]-, forming the hybrid crystal [(18-Crown-6)K][MoOCl4(H2O)]. It crystallizes in orthorhombic crystal system with Pnma space group. The Mo(V) possesses one d-electron (d1) in C4v point group symmetry in the [MoOCl4(H2O)]- polyhedra. This electronic configuration leads to multiple spin-allowed d-d transitions along with a ligand to metal charge transfer (LMCT) resulting into multiple optical absorption bands in the near UV-visible-near infrared (NIR) region. The lowest energyd-dtransition via 2E to2B2 leads to NIR PL with peak at 952 nm, but with a poor intensity at room temperature.

N-ZrS3/p-ZrOS Photoanodes with NiOOH/FeOOH Oxygen Evolution Catalysts for Photoelectrochemical Water Oxidation.

Photoelectrochemical water splitting offers a promising approach for carbon neutrality, but its commercial prospects are still hampered by a lack of efficient and stable photoelectrodes with earth-abundant materials. Here, we report a strategy to construct an efficient photoanode with a coaxial nanobelt structure, comprising a buried-ZrS3/ZrOS n-p junction, for photoelectrochemical water splitting. The p-type ZrOS layer, formed on the surface of the n-type ZrS3 nanobelt through a pulsed-ozone-treatment method, acts as a hole collection layer for hole extraction and a protective layer to shield the photoanode from photocorrosion. The resulting ZrS3/ZrOS photoanode exhibits light harvesting with good photo-to-current efficiencies across the whole visible region to over 650 nm. By further employing NiOOH/FeOOH as the oxygen evolution reaction cocatalyst, the ZrS3/ZrOS/NiOOH/FeOOH photoanode yields a photocurrent density of ~9.3 mA cm-2 at 1.23 V versus the reversible hydrogen electrode with an applied bias photon-to-current efficiency of ~3.2% under simulated sunlight irradiation in an alkaline solution (pH = 13.6). The conformal ZrOS layer enables ZrS3/ZrOS/NiOOH/FeOOH photoanode operation over 1000 hours in an alkaline solution without obvious performance degradation. This study, offering a promising approach to fabricate efficient and durable photoelectrodes with earth-abundant materials, advances the frontiers of photoelectrochemical water splitting.

Electronic, optical, and thermoelectric behaviour of KCuX (X = S, Se, Te) monolayers.

In the past few decades, two-dimensional (2-D) materials gained huge deliberation due to their outstanding electronic and heat transport properties. These materials have effective applications in many areas such as photodetectors, battery electrodes, thermoelectrics, etc. In this work, we have calculated structural, electronic, optical, and thermoelectric properties of KCuX (X = S, Se, Te) monolayers (MLs) with the help of first-principles-based calculations and semi-classical Boltz- mann transport equation (BTE). The phonon dispersion calculations demonstrate the dynamical stability of the KCuX (X = S, Se, Te) MLs. Our results show that the monolayers of KCuX (X = S, Se, Te) are semiconductors with band gaps of 0.193 eV, 0.26 eV, and 1.001 eV respectively, and therefore they are suitable for photovoltaic applications. The optical analysis illustrates that the maximum absorption peaks of the KCuX (X = S, Se, Te) MLs are located in visible and ultraviolet (UV) regions, which may serve as a promising candidate for designing advanced optoelectronic devices. Furthermore, thermoelectric properties of the KCuS and KCuSe MLs, including See- beck coefficient, electrical conductivity, electronic thermal conductivity, power factor, and figure of merit, are calculated at different temperatures 300 K, 600 K, and 800 K. Additionally, we also focus on the analysis of Gru ̈neisen parameter and various scattering rates to further explain their ultra-low thermal conductivity. Our results show that KCuS and KCuSe possess ultra-low lattice thermal conductivity value of 0.15 Wm-1K-1 and 0.06 Wm-1K-1 respectively, which is lower than those of recently reported KAgSe (0.26 Wm-1K-1 at 300 K) and TlCuSe (0.44 Wm-1K-1 at 300 K), indicating towards the large value of ZT. These materials are found to possess desirable thermoelectric and optical properties, making them suitable candidates for efficient thermoelectric and optoelectronic device applications.

Photoluminescence and photocatalytic activity of sol gel synthesized Mg doped TiO2 nanoparticles

The influence of magnesium doping on the optical properties, structural characteristics, and photocatalytic performance of TiO2 nanoparticles was investigated. Pure and Mg-doped TiO2 nanoparticles with varying weight percentages of magnesium were synthesized via the sol–gel method, followed by calcination at 100 °C for 12 h and annealing at 400 °C for 2 h to promote crystallization. X-ray diffraction (XRD) analyses confirmed the formation of crystalline mixed phases of anatase and rutile TiO2 nanoparticles, exhibiting their crystalline nature upon synthesis. Scanning electron microscopy (SEM) images were employed to study the morphological features of the samples, while energy dispersive spectroscopy (EDS) provided insights into their elemental composition. Photoluminescence (PL) emission spectra revealed ultraviolet (UV) to visible region emission for both pure and doped TiO2 samples. The photocatalytic activity was evaluated by monitoring the degradation of methyl orange under natural sunlight irradiation, elucidating the impact of visible light exposure. Furthermore, investigations were conducted to assess the influence of catalyst loading, initial dye concentration, and pH of the dye solution on the methyl orange removal efficiency. The 3 wt% Mg doped TiO2 exhibited 95 % of decolorization of Methyl Orange. X-ray photoelectron spectroscopy measurements was performed to verify the elemental composition and chemical valence states of each element. The scavenger test in photodegradation mechanism revealed that the main reactive species was superoxide species. The electron species resonance (ESR) measurement demonstrate that the synthesized sample shows the low spin state of Mg2+ in TiO2. The correlation between Mg doping on photocatalytic activity and crystal structure were studied. Theoretical calculations were performed to gain insights into the potential mechanism underlying the tuning of luminescent and photocatalytic properties of Mg-doped TiO2 nanoparticles, enabling a comprehensive discussion.

Nanoscale Imaging of Palladium-Enhanced Photocatalytic Reduction of 4-Nitrothiophenol on Tungsten Disulfide Nanoplates.

Two-dimensional (2D) dichalcogenides are modern nanomaterials with unique physical and chemical properties. These materials possess band gaps in the infrared and visible regions of the electromagnetic spectrum that can be tuned by their molecular composition. Excitons generated as a result of such light-matter interactions are capable of catalyzing chemical reactions in molecular analytes present on the dichalcogenide surfaces. However, the photocatalytic properties of such nanomaterials remain poorly understood. In the current study, we utilize tip-enhanced Raman spectroscopy (TERS) to examine photocatalytic reduction of 4-nitrothiophenol (4-NTP) to p,p'-dimercaptoazobisbenzene (DMAB) on tungsten disulfide (WS2) nanoplates and WS2 coupled with palladium nanoparticles (WS2@PdNPs). Our results indicate that although both WS2 and WS2@Pd were capable of reducing 4-NTP into DMAB, the metallic hybrid demonstrated much greater yield and rates of DMAB formation compared to WS2 nanoplate. These results indicate that coupling of catalytic metals to dichalcogenides could be used to enhance their catalytic properties.

Computational Justification Towards Detection of Dual Anions on a Single Molecular Platform: The Role of Solvent in Decoration of Dual Channels

ABSTRACTRatiometric optical detection of analytes is a convenient strategy as the technique is devoid of relative error and background correction. Herein, solvent‐guided ratiometric optical recognition of fluoride and bisulfate anions by a low‐cost, “off‐the‐shelf” bioactive molecule, harmane (HRH) is thoroughly explored. Interestingly, solvent plays a dynamic role in the selective recognition of the dual anions via the dual channels of HRH in an intelligent manner. The probe displays high‐fidelity recognition behavior towards fluoride ion in an aprotic solvent (acetonitrile) and towards bisulfate ion in a protic environment (acetonitrile/water; 5:1; v/v). Both the channels of HRH are very selective for a particular anion (F−/HSO4−) in a specific solvent. Organized and comprehensive theoretical calculation denotes that hydrogen bonding between the acidic pyrrolic proton of HRH and fluoride for the first channel and the acidic proton of bisulfate and the pyridinic nitrogen for the second channel of HRH led to the formation of a hydrogen‐bonded ion pair (HBIP). Consequently, significant optical changes are observed in the visible region, which is convenient for real‐life detection of F− and HSO4− independently. The essential role of solvent in tuning the dual channels of HRH is an important artifact in the literature of fundamental photochemistry.

Novel Indolenine-Based hemicyanine dyes with extended π-Linker and auxiliary donor as potential Photosensitizers: Synthesis, Photophysical, electrochemical and computational Insights

Three novel hemicyanine dyes, D1-D3, were synthesized successfully based on dimethylaniline (DMA) and TPA donors and a carboxylated indolium vinyl acceptor linked through benzene unit as an extended π-spacer or through PTZ unit as an auxiliary donor to form the D1-π-A, D2-π-A & D2-D3-A systems, respectively. A multi-step process was conducted to yield the desired donor and acceptor intermediates. These were finally coupled through the Suzuki-Miyaura coupling and Knoevenagel condensation reactions to obtain the desired target dyes. A panchromatic response and a bathochromic shift of the ICT band maxima in the visible region were observed with the lowest band gap energy, Eg = 1.71 eV and λabs., max. = 590 nm, given by dye D3, were attributed to the presence of the auxiliary donor, PTZ. However, due to the high coplanarity of dye D1 it showed the highest absorptivity value of ε = 36462 M−1cm−1. The HOMO and LUMO levels are within the range suitable for smooth dye regeneration and electron ejection, EHOMO = -5.37 to −5.18 eV, and ELUMO = -3.47 to −3.27 eV. The density functional theory (DFT) and time-dependent TD-DFT at the B3LYP/6-31G(d,p) level were conducted to explore the bridged effect on geometric and TD-BHandH/6-31G(d,p) for optoelectronic properties.

Synthesis and characterization of zinc-doped hematite nanoparticles for photocatalytic applications and their electronic structure studies by density functional theory

Hematite nanoparticles doped with 1, 3 and 5 % Zn (all % are in molar) were prepared using mechanical alloying. Morphological and phase structure studies using scanning electron microscopy and X-ray diffraction showed nanoparticles possessing a semi-spherical shape and particle size of <50 nm crystallized in rhombohedral structure. The lattice parameters of hematite increased upon Zn doping. The energy-dispersive X-ray and Fourier-transform infrared results demonstrated that Zn was successfully incorporated. The optical behavior of nanoparticles was examined by UV–Vis diffuse reflectance spectroscopy and revealed that Zn doping increased the absorption intensity in the visible light region and decreased the band gap from 1.95 (hematite) to 1.83 eV (3 % Zn). Methylene blue dye degradation by the 3 % Zn sample proved doubling of the photocatalytic activity due to electronic structure modification upon Zn doping. First principles studies using density functional theory performed to investigate the effect of Zn on the electronic band structure of hematite showed that Zn doping caused band gap reduction, causing formation of new energy states, mainly above the valence band. Eventually, the enhancement of Urbach energy and reduction of effective mass, respectively accountable for increasing the relaxation time and mobility of charge carriers, were considered the two main mechanisms regarding the increased photocatalytic behavior of hematite by Zn doping.

Understanding the optoelectronic and vibrational properties of MB[formula omitted]O[formula omitted], using density functional theory, where M = Yb or Ce

This work aims to use density functional theory (DFT) and density functional perturbation theory (DFPT) to study the structure, optoelectronics, phonon dispersion and energetic stability of two new tetraborates, MB4O7, where M = Yb or Ce. The estimated values of the band gap energy (Eg) and power conversion efficiency (PCE) for the systems were calculated. The Shockley-Queisser was also taken into account to measure the maximum theoretical efficiency of a photovoltaic source cell based on a p-n union. The estimated average gap energy values for the YbB4O7 and CeB4O7 systems, calculated using the GGA-PBE, HSE06, and GGA+U functionals, were 3.64 eV and 0.97 eV, respectively. The average PCEs calculated for the YbB4O7 and CeB4O7 systems were 11.28% and 25.66%, respectively. The PCE and energy stability suggest that CeB4O7 may be a more viable candidate for a solar device than YbB4O7, at least in terms of these specific parameters. The results reported here, as well as those related to absorption calculations, showed that the structures have optical responses in the visible region, suggesting that both systems can be used as optoelectronic devices and in solar cell designs.

Low-loss metasurfaces based on discretized meta-atoms

Metasurfaces are established tools for manipulating light and enhancing light-matter interactions. However, the loss of conventional meta-atoms usually limits the performance potential of metasurfaces. In this study, we propose a class of metasurfaces based on discretized meta-atoms able to mitigate the radiative and intrinsic losses. By discretizing meta-atoms, we reduce the loss of metal metasurfaces to levels comparable to dielectric metasurfaces in the short-wavelength infrared region at the surface lattice resonance mode. Furthermore, we propose a coupling model to explain the observed reduction in loss in full agreement with the results obtained from finite-element method. We also reproduce this phenomenon using dielectric metasurface at electric and magnetic resonances in the visible region. Our finding offers valuable insights for the design and application of metasurfaces, while also providing theoretical implications for other resonance fields beyond metasurfaces.

Histidine-based hybrid perovskites as promising materials for wide wavelength photodetection

Layered 2D hybrid organic-inorganic perovskites (2D-HOIPs) exhibit a distinctive array of properties, including remarkable structural flexibility, enhanced resistance to moisture, and optoelectronic characteristics valuable for practical applications. Consequently, these materials are now widely acknowledged as pivotal components in optical and optoelectronic technologies. However, a significant drawback of 2D-HOIPs is their wide band gaps that has hindered their widespread application in optoelectronic devices. In this work we address this limitation by offering a novel series of 2D mixed-halide tin-based HOIPs with general formula (L-HisH)2SnBrxI4−x (where L-His = L-histidine, x = 4, 3.37, 1.70, 0.56, 0.44, and 0) for which the band gap can reach record narrow values, which are not typical for 2D-HOIPs. These compounds can be easily obtained in wide compositional range by implementing halide substitution approach. Each hybrid perovskite features a chiral structure imparted by chiral L-histidinium(+) cations interleaved between corner-shared tin halide octahedra, organized into single-layer thin inorganic slabs. Crucially, these new materials provide a high degree of flexibility in tuning their band gaps throughout the entire visible light spectrum, encompassing a range between 1.82 and 3.05 eV. As a “proof-of-concept”, we created a prototype HOIPs photodetector in which this HOIP was used as an active layer. It is noteworthy that the band gap of pure iodide perovskite is surprisingly narrow for this class of materials. The production of semiconductor materials with a variable width of the optical bandgap is the key to more versatile and diverse applications of these materials in the active components of modern optoelectronic devices. For the obtained prototype, light detection is observed in the wide range covering UV, visible and near-IR regions, marking a record achievement for 2D-HOIPs. Beyond photodetectors, these new histidine-based perovskites hold promise for applications in various other optoelectronic devices, including solar cells, photodiodes, phototransistors, polarized light detectors, and more.