Ultraviolet Region Research Articles

Unveiling the potential of lead-free KInBr3 and RbInBr3 perovskites: a breakthrough in optoelectronic and photovoltaic performance through DFT (HSE hybrid functional) and SCAPS-1D simulations

ABSTRACT Lead-free halide perovskites are emerging as promising materials for solar cells due to their exceptional properties. KInBr₃ and RbInBr₃ are particularly notable, showing great potential for lead-free perovskite solar cells (PSCs). Using density functional theory (DFT) with the VASP framework, we investigated their structural, electronic, and optical properties. Both materials exhibit direct band gaps, with 0.93 eV for KInBr₃ and 0.77 eV for RbInBr₃, calculated using the hybrid HSE functional. The density of states (DOS) analysis reveals that the In s/p orbitals dominate the band edges, making these materials suitable for photovoltaic applications. Optical studies confirm strong light absorption in the visible and ultraviolet regions. Furthermore, SCAPS-1D simulations for a solar cell with the structure Ag/MoO₃/KInBr₃/ZnO/ITO yielded a power conversion efficiency (PCE) of 30.25%, demonstrating the exceptional potential of KInBr₃ for high-performance solar energy technologies.

2D MoS2 for detection of COVID-19 biomarkers – a first-principles study

Abstract This study investigates specific compounds in the breath that can indicate COVID-19 and lung cancer. Heptanal (C7H14O), acetone (C3H6O), propanol-1 (CH3CH2CH2OH), butanal (C3H7CHO), isopropanol (CH3CHOHCH3), acetaldehyde (CH3CHO), 2,4-octadiene (C8H14), and ethyl butyrate (C6H12O2) were studied. We analyze how these compounds interact using two-dimensional (2D) 2H and SV-MoS2 monolayers through first-principles calculations. Van der Waals forces bind all VOCs on the MoS2 surface in vacuum and humid conditions. The decrease in the band gap of the MoS2-VOC complex in these environments enhances sensitivity. The complexes of 2,4-octadiene, propanol-1, and ethyl butanoate are more conductive because their work function is lower, and their V(z) shift is more significant. The adsorption isotherm demonstrates the potential for surface reuse in sensing applications. The study confirms high sensitivity (>85%) and fast recovery time (up to 70 femtoseconds) for detecting in visible (VL) and ultraviolet (UV) regions. Mainly, 2,4-octadiene exhibits high sensitivity and selectivity. In conclusion, the 2H and SV MoS2 monolayers effectively detect COVID-19 and lung cancer markers in vacuum and humid conditions.

Effect of Fe doping on electronic structure and optical properties of two-dimensional CuI

The effects of different concentrations of Fe doping on the photoelectric properties of two-dimensional (2D) CuI semiconductor are studied based on the first-principles calculation method. The results show that both intrinsic 2D CuI and Fe-doped 2D CuI are direct band gap semiconductors. The total state density and partial wave state density of 2D CuI doped with different concentrations of Fe show that the increase in the number of energy bands at Fermi level is due to the influence of Fe-d and Fe-p orbital contributions after Fe doping, which can improve the conductivity of 2D CuI. With the increase of Fe doping concentration, the peak value of <i>ε</i><sub>1</sub> decreases gradually, and the peak value moves toward the high-energy end near the relatively high energy 3 and 6 eV, and the greater the concentration, the more obvious the shift is. These results indicate that Fe doping can enhance the high temperature resistance of 2D CuI. When a small amount of Fe is doped, the <i>ε</i><sub>2</sub> peak value increases, indicating that the ability of material to absorb electromagnetic waves is enhanced, which can stimulate more conductive electrons, and with the increase of Fe doping concentration, the absorption capability decreases, so the conductivity of 2D CuI is inhibited. The absorption coefficient of intrinsic 2D CuI and Fe-doped 2D CuI indicate that the semiconductor has strong ability to absorb photons in the ultraviolet region. The 2D CuI reflection coefficient of doped Fe atoms increases gradually with the increase of metallic properties of doped elements. This study provides theoretical reference for applying the 2D semiconductor materials and 2D CuI to optoelectronic devices. All the data presented in this paper are openly available at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.57760/sciencedb.j00213.00060">https://doi.org/10.57760/sciencedb.j00213.00060</ext-link>.

The optoelectronic properties of boron nitride nanotubes of armchair (7, 7) and zigzag (12, 0) types: A theoretical study

In this article, the electronic and optical properties of single-walled boron nitride nanotubes (SWBNNTs) in zigzag (12, 0) and armchair (7, 7) configurations were examined using density functional theory (DFT) with the Vienna Ab initio Simulation Package (VASP). The analysis shows that SWBNNTs exhibit electronic characteristics with a density of states and an electronic band gap around 4 eV. Regarding optical properties, the calculations reveal key features such as absorption, reflection, and dielectric constant, with a notably strong absorption peak in the ultraviolet region. These results highlight the potential of SWBNNTs for applications in optoelectronic devices.

A Study on the Helium Selenium Laser

Metal-vapour lasers include helium-selenium lasers. This laser operates in a similar manner to the helium cadmium laser. When selenium transitions between its excited states, spontaneous emission takes place. This laser emits radiation at up to 24 distinct wavelengths. The wavelengths are located in the spectrum's red and ultraviolet regions.[22]

Enhanced Light Response Performance of Ceria-Based Composites with Rich Oxygen Vacancy.

Increasing the concentration of oxygen vacancies in ceria-based materials to solve the bottleneck of their applications in various fields has always been a research hotspot. In this paper, ceria-based cerium-oxygen-sulfur (Ce-O-S) composites that were composed of CeO2, Ce4O4S3, and Ce2(SO4)3 were synthesized by a precipitation method. The compositional, structural, morphological, and light response characteristics of prepared Ce-O-S composites were investigated by various characterization techniques. The molar ratio of oxygen vacancies to lattice oxygen can reach a maximum of 1.83 with Ce-O-S composites. The band gap values of the Ce-O-S composites were less than 3.00 eV, and the minimum value was 2.89 eV (at pH 12), which successfully extended the light response range from the ultraviolet light region to the short-wave blue light region. The remarkable light response performance of Ce-O-S composites can be mainly attributed to the high proportion of oxygen vacancy. Moreover, the higher proportion of oxygen vacancies can be attributed to the doping of Ce (+3) and S (-2) in the lattice of CeO2, and the synergistic effect of CeO2, Ce4O4S3, and Ce2(SO4)3. Moreover, the ceria-based Ce-O-S composites with rich oxygen vacancy in this research can be applied in light blocking, photocatalysis, and other related fields.

Functionalized hBN Quantum Dots as Optical Limiters in the Ultraviolet Region

Functionalized hBN Quantum Dots as Optical Limiters in the Ultraviolet Region

Revealing Self‐Driven Broadband Photodetection Using Heterojunction of Bi2Se3 and Low‐Temperature Laser Molecular Beam Epitaxy Grown GaN on SrTiO3 (100) Substrate

AbstractOptoelectronic properties of GaN are underexplored on good lattice matching SrTiO3 (STO) due to STO's instability at the high GaN growth temperatures (800–1100 °C) required by traditional techniques. Here, GaN is grown on STO (100) at lower temperatures (500, 600, and 700 °C) using the laser‐assisted molecular beam epitaxy (LMBE) technique, and their morphological, crystalline, optical, and photodetection properties are analyzed. Further, heterojunction of Bi2Se3 thin film (bandgap of 0.3 eV) is formed on the highest photo‐responsive LMBE‐GaN/STO to fabricate a self‐powered broadband photodetector. The fabricated self‐powered heterojunction photodetectors device exhibits a high responsivity of 2.93 × 102 mAW−1 in ultraviolet region and a notable responsivity of 2.3 and 12 mAW−1 in visible and near‐infrared spectral regions, respectively. In addition, photoresponse properties of fabricated devices on bare LMBE‐GaN and its heterojunction are compared under UV light illumination. The photoresponsivity of heterojunction in UV region is estimated to be 3.05 × 104 mAW−1, which is enhanced by 100% compared to bare LMBE‐GaN. Combining the unique optoelectronic properties of GaN and rigidity of STO, epitaxy of GaN on STO enables construction of robust photodetector devices. Further, Bi2Se3‐functionalized GaN can provide self‐sufficient and high‐quality futuristic optoelectronics devices.

Highly Sensitive InSe Nanosheet Ultraviolet Photodetector Realized Via an Asymmetric Fabry–Pérot Structure

AbstractDue to the wavelength‐dependent absorption, narrow bandgap semiconductors show potential application in ultraviolet (UV) photodetection by thinning. However, the limited absorption in the thinner layer retards their application in high‐performance photodetection. In this paper, the fabrication of an asymmetric Fabry–Pérot (F–P) structure is reported by planar stacking of InSe layer, Al2O3 spacer, and Al back reflector. For the selective absorption enhancement in UV region, the Al2O3 thickness is optimized to be 39 nm by finite element method (FEM). The device presents a peak response at 265 nm illumination, showing the photo‐to‐dark current ratio (Ilight/Idark) of 719. Responsivity (R) and photoconductive gain (G) reach 11.7 A W−1 and 54.7 at the weak light intensity of 0.03 mW cm−2, respectively, which are two orders of magnitude higher than those of the device without the asymmetric F–P structure, revealing the remarkably enhanced absorption. This work shows well compatibility with the manufacturing processes for 2D semiconductor‐based photodetectors and provides a simple and versatile strategy for the application of 2D narrow bandgap semiconductors in high‐performance UV photodetectors.

PbS Quantum Dot-Based Optoelectronic Memristors toward Multi-Task Reservoir Computing.

The rise of big data and the internet of things has driven the demand for multimodal sensing and high-efficiency low-latency processing. Inspired by the human sensory system, we present a multifunctional optoelectronic-memristor-based reservoir computing (OM-RC) system by utilizing a CuSCN/PbS quantum dots (QDs) heterojunction. The OM-RC system exhibits volatile and nonlinear responses to electrical signals and wide-spectrum optical stimuli covering ultraviolet, visible, and near-infrared (NIR) regions, enabling multitask processing of dynamic signals. The OM-RC system accurately performs health monitoring through dynamic electroencephalogram and electrocardiogram signal analysis and achieves object and traffic trajectory recognition for intelligent driving under challenging conditions like foggy environments. By collaboratively using the NIR perception and trajectory recognition, we develop a human-computer interaction authentication system that integrates finger veins and motion behaviors of humans, significantly enhancing the security of traditional fingerprint anticounterfeiting systems. This work demonstrates the potential of QD-based optoelectronic-memristor for multitask in-sensor processing applications.

K6NaCaRe2(B5O10)3 (Re = Y, Lu): Two NLO Compounds Exhibiting a Short Absorption Edge in the A7-xA'xAeRe2(B5O10)3 (x = 0, 1) Family.

The discovery and synthesis of new NLO materials in the ultraviolet (UV) region are crucial to developing laser technology. The chemical substitution strategy is an effective pathway to design potential UV or DUV NLO crystals. Herein, two new compounds, K6NaCaY2(B5O10)3 and K6NaCaLu2(B5O10)3, have been synthesized using KB5O8·4H2O as the template. Their crystal structures feature a three-dimensional (3D) [Re2(B5O10)3]∞ framework consisting of [B5O10] groups and [ReO6] octahedra, and the remainder of metal cations fill the void to control charge balance and maintain the stability of the crystal structure. Both K6NaCaY2(B5O10)3 and K6NaCaLu2(B5O10)3 crystallize in the acentric space group R32, so they exhibit an SHG effect, and the value is ∼0.5 × KDP (KH2PO4). Meanwhile, they show a phase-matching ability. Due to the participation of alkali metals, alkaline earth metal, and [B5O10] unit, the title compounds possess short absorption edges of ∼230 nm. In addition, they have high thermal stability and can be stable up to 931 °C. These results confirm the effectiveness of the chemical substitution strategy for designing NLO compounds, and then the two compounds can potentially serve as good UV NLO materials.

Low cost ultraviolet LED using downshifting phosphors

Phosphor-converted LEDs (pc-LEDs) have been employed for solid-state lighting applications. The use of phosphor helped in achieving desirable properties such as good color rendition (CRI), coordinated color temperature (CCT), etc. White LED lamps have been fabricated using downshifting phosphors. However, few efforts have been made to develop ultraviolet (UV) emitting LEDs using downshifting phosphors. On the other hand, numerous reports are available in the literature on directly UV emitting LED. Such LEDs are available commercially. Cost and efficiencies of directly UV emitting LED chips vary. It could be useful to coat suitable phosphors of low cost, excitable by shorter wavelengths on UV emitting chips to obtain pc-LED emitting at longer wavelength UV region. This concept is demonstrated here by using suitable phosphors and a chip emitting at 275 nm to obtain pc-UVLED emitting in 300–340 nm range.

Determination of Three Metal Ions (Cu2+, Pb2+, Cd2+) by Ultraviolet-visible Spectroscopy

Abstract The objective of this article review is the determination of the concentration or amount of trace metal ions using Ultraviolet-visible spectrophotometry. The maximum absorption wavelength (λ-max) of the three metallic ions (Cu+2, Pb+2, and Cd+2) that I have highlighted are equivalent to (755 nm, 100-380 nm, and 323.9 nm) when they are alone, However, when these metal ions interact with a reagent, the λ-max of each metal ion differs. Ultraviolet-visible (UV-Vis) spectrophotometry is deemed an efficient method for both qualitative and quantitative analysis of pollutants in a water environment. This succinct statement outlines the focus of the article review, emphasizing the application of UV-Vis spectrophotometry for analyzing trace metal ions in water samples. Also, the analytical technique measures the amount of single-color lighting absorbed via a colorless substance in the close ultraviolet light region of a range (between 200 and 400 nm). The process required to ascertain the “identity, strength, quality and purity” of such chemicals is included in the pharmaceutical analysis. Using calibration curves and absorption band correlation with certain ions to find concentration metal ion or analyte in the sample. A bibliometric analysis classifies the top 10,000 cited UV-Vis papers (2016-2017) into four clusters: nanoparticles, photocatalysis, crystals, and biological interaction of Ag and Au nanoparticles.

Bifunctional Design of Ferroelectric-Order and Band-Engineering in Cu:KTN Crystal for Extended Self-Powered Photoelectric Response.

Photoelectric conversion in ferroelectric crystals can support many important applications in modern on-chip technology, but suffering from two problems, low responsive current and narrow responsive range. Especially, wide-gap ferroelectric oxides are only active at short-wavelength ultraviolet region with weak photocurrent at nanoampere levels. Here, a bifunctional design strategy of ferroelectric-order and electronic-band to improve the photocurrent and extend the responsive range simultaneously, is proposed. In a Cu-doped KTa1- xNbxO3 (KTN) perovskite crystal, a conductive channel is constructed by "head-to-head" ferroelectric domains, associated with the emergence of micrometer-scale supercells. In addition, the introduction of Cu+ ion can induce defect levels, thus extending the responsive range beyond the inherent absorption of pure KTN. Through rational device optimization, a record self-powered responsivity of 5.23 mA W-1 is realized in Cu:KTN photodetector, which is two orders of magnitude higher than undoped KTN crystal. The temperature-dependent light diffraction and photocurrent show that the ferroelectric-order is dominated in this photoresponse behavior. Moreover, Cu:KTN detector is active in the broadband range from 390 to 1030 nm, covering ultraviolet, visible, and near-infrared regions. This work provides an effective method for the design of next-generation self-powered photodetectors with ultrahigh responsivity and ultrawide responsive range.

First-Principles insights into ferromagnetic, optoelectronic and dynamical properties of Eu/Er Co-doped AlGaN

Abstract In this thorough investigation, we analyze the complex electronic, magnetic, and structural properties of wurtzite-structured aluminum gallium nitride (Al0.125Ga0.75N) when co-doped with the rare-earth elements erbium and europium. Leveraging a modified LSDA+U approach that adeptly captures the pivotal interactions within the 4f shell, our findings unveil that the co-doped AlGaN exhibits distinct semiconducting behavior. Remarkably, in stark contrast to its pristine Al0.125Ga0.75N counterpart, the co-doped material manifests an indirect band gap whose value is notably reduced. This intriguing phenomenon of ferromagnetism observed in the co-doped system can be attributed to the intricate interplay between the f-p and p-d states, culminating in the formation of hybridized f-p-d orbitals. Our investigation further elucidates the intricate hybridization of various orbitals at the valence band maximum (VBM), including the harmonious fusion of p-d orbitals derived from Eu-5d, Er-5d, and N-2p. Notably, the magnetic moment exhibits a pronounced localization at the Eu and Er sites, attaining substantial values of 5.90 μB and 2.99 μB, respectively. Moreover, our comprehensive exploration encompasses the calculation of the real and imaginary components of the dielectric function, refractive index, and extinction coefficient, spanning an impressive photon energy range of up to 12 eV. Significantly, in the ultraviolet region of the optical spectrum, the imaginary part of the Eu and Er co-doped Al0.125Ga0.75N unveils a pronounced absorption coefficient, a pivotal property with far-reaching implications for optoelectronic applications.


Cr3+ doped ZnGa2O4 micro-flowers as stable saturable absorber media

Abstract Micro-flowers of Cr3+ doped ZnGa2O4, a spinel compound with high chemical and thermal stability is synthesized by hydrothermal method. Flower-like structures in the micrometre range made up of secondary nanoflakes are evident from the field emission scanning electron microscope (FESEM) images. X-ray photoelectron spectroscopy (XPS) studies confirm the presence of Cr3+ dopants. The steady-state optical characterizations show higher absorbance of the samples in the ultraviolet (UV) region. Due to introduction of the d-d electron transition states of Cr3+ ions, ZnGa2O4:Cr3+ exhibits a prominent red near infrared (NIR) luminescence. Optical nonlinearity studies show that Cr3+ doping changes the nonlinear absorption from reverse saturable absorption (RSA) to saturable absorption (SA). This is due to the introduction of an excitation band owing to 4T1-4A2 transition of Cr3+ ion.

C(NH2)3]2S2O6: A SBBO-Like Dithionate Crystal with Large Optical Anisotropy.

Investigating ultraviolet (UV) birefringent crystals is a focal point of research in recent years. The development of superior birefringent materials faces substantial challenges, primarily due to the need to pinpoint optimal fundamental building blocks and to perfect their geometric arrangement within the crystal lattice. By selecting a planar π-conjugated [C(NH2)3] group and a staggered [S2O6] group, we have successfully synthesized an organic-inorganic hybrid crystal, [C(NH2)3]2S2O6. Similar to the famous inorganic crystal Sr2Be2B2O7 (SBBO), [C(NH2)3]2S2O6 exhibits a two-dimensional double-layered crystal structure connected by N-H···O hydrogen bonding. Due to the ideal spatial arrangements of the planar π-conjugated [C(NH2)3] group, this crystal displays a large birefringence (0.150 at 546 nm) among sulfate derivatives in the short-wave UV region. Meanwhile, [C(NH2)3]2S2O6 has a large band gap of 5.23 eV. This work indicates that the [S2O6] unit, acting as a direct structural motif, is beneficial for the discovery of UV birefringent crystals.

Ultrathin transparent indium tin oxide-based electrodes for enhanced performance of perovskite solar cells

Abstract Perovskite solar cells (PSCs) have been given much attention in photovoltaics-based power generation, particularly in building integrated photovoltaics (BIPV) applications due to their lightweight and promising technical performance. PSCs exhibit remarkable transparency to visible light, which makes them an ideal candidate for BIPV applications such as glass-based solar facades and clear solar windows. As the PSC is yet an immature technology, much research is still required to validate its visibility and cost-effectiveness for different applications including electrical vehicles. This paper takes one step forward in achieving this goal by presenting a new ultrathin transparent electrodes (UTE) design that comprises a square patch layout to improve the performance of transparent conductive materials. The proposed electrode design is aimed to improve the absorption of the material in the ultra-violet (UV) region with high optical transparency. To assess the angular dependence on the absorption characteristics, both transverse magnetic and transverse electric modes are studied at various oblique angles of incident light. Furthermore, interference theory is applied numerically to validate the proposed UTE design. The impact of various geometric parameters including period, ground height, spacer height, and top square resonator length on the performance of the proposed UTE layout is investigated through detailed simulation analysis. Moreover, surface electric field patterns are analyzed to understand the absorption mechanism of the proposed UTE. Results reveal the effectiveness of the proposed structure for various BIPV applications including electric vehicles, wearable electronics, and tandem devices.

The Study of Tunable Excitation Independent and Dependent Photoluminescence Behaviour of P-Functionalized Carbon Dots

In this article, excitation independent and dependent fluorescence properties of surface functionalized carbon dots were studied. The samples were synthesized using a biomass derived Indian gooseberry as carbon precursor via microwave irradiation technique. Concentrated phosphonic acid is utilized as a surface passivator for carbon dots. The formation of spherical carbon dots in the size range of 6 to 12 nm was shown by transmission electron microscopy images. Raman and Fourier transform IR spectroscopies suggest the creation of highly disordered sp3carbon atoms including presence of surface functional groups and interaction of phosphorus with surface of carbon core. From the UV-visible absorption study, absorbance bands at 231 nm and 283 nm attributed to π-π* molecular transitions from carbon core are found. From the photoluminescence measurements, both excitation independent and excitation dependent tunable fluorescence is obtained from ultraviolet to visible (yellow) region of light respectively. The involvement of carbon core electronic states and surface modifier states are responsible for the origin of luminescence and their distinguished nature. The mechanism is discussed and emitted colour are confirmed by CIE plot. The relative quantum yield of the P-functionalized carbon dots is found to be 18.9% with reference to quinine sulfate. The fluorescence in ultra-violet and visible regions is applicable for bioimaging and potential antimicrobial activities.

Controlled tuning of HOMO and LUMO levels in supramolecular nano-Saturn complexes.

Optoelectronics usually deals with the fabrication of devices that can interconvert light and electrical energy using semiconductors. The modification of electronic properties is crucial in the field of optoelectronics. The tuning of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and their energy gaps is of paramount interest in this domain. Herein, three nano-Saturn supramolecular complex systems are designed, i.e., Al12N12@S-belt, Mg12O12@S-belt, and B12P12@S-belt, using S-belt as the host and Al12N12, Mg12O12, and B12P12 nanocages as guests. The high interaction energies ranging from -22.03 to -63.64 kcal mol-1 for the complexes demonstrate the stability of these host-guest complexes. Frontier molecular orbital (FMO) analysis shows that the HOMO of the complexes originates from the HOMO of the host, and the LUMO of the complexes originate entirely from the LUMO of the guests. The partial density of states (PDOS) analysis is in corroboration with FMO, which provides graphical illustration of the origin of HOMO and LUMO levels and the energy gaps. The shift in the electron density upon complexation is demonstrated by the natural bond orbital (NBO) charge analysis. For the Al12N12@S-belt and B12P12@S-belt complexes, the direction of electron density shift is towards the guest species, as indicated by the overall negative charge on encapsulated Al12N12 and B12P12. For the Mg12O12@S-belt complex, the overall NBO charge is positive, elaborating the direction of overall shift of electronic density towards the S-belt. Electron density difference (EDD) analysis verifies and corroborates with these findings. Noncovalent interaction index (NCI) and quantum theory of atoms in molecules (QTAIM) analyses signify that the complexes are stabilized via van der Waals interactions. Absorption analysis explains that all the complexes absorb in the ultraviolet (UV) region. Overall, this study explains the formation of stable host-guest supramolecular nano-Saturn complexes along with the controlled tuning of HOMO and LUMO levels over the host and guests, respectively.