Photon Absorption Coefficient Research Articles

Structure-Property Correlations in CZTSe Domains within Semiconductor Nanocrystals as Photovoltaic Absorbers.

Semiconductor nanocrystals (NCs) are promising materials for various applications. Two of four recently identified CuαZnβSnγSeδ (CZTSe) domains demonstrate metallic character, while the other two exhibit semiconductor character. The presence of both metallic and semiconductor domains in one NC can hugely benefit future applications. In contrast to traditional band gap studies in the NC community, this study emphasizes that NC domain interfaces also affect the electronic properties. Specifically, the measured band gap of a tetrapod-shaped CZTSe NC is demonstrated to originate from two specific domains (tetragonal I and monoclinic P1c1 Cu2ZnSnSe4). The heterojunction between these two semiconductor domains exhibits a staggered type-II band alignment, facilitating the separation of photogenerated electron-hole pairs. Interestingly, tetrapod NCs have the potential to be efficient absorber materials with higher capacitance in photovoltaic applications due to the presence of both semiconductor/semiconductor interfaces and metal/semiconductor "Schottky"-junctions. For the two photo-absorbing domains, the calculated absorption spectra yield maximum photon-absorption coefficients of about 105 cm-1 in the visible and UV regions and a theoretical solar power conversion efficiency up to 20.8%. These insights into the structure-property relationships in CZTSe NCs will guide the design of more efficient advanced optical CZTSe materials for various applications.

Impact of SWCNTs and CMCS on efficacy of anastomosis and optical properties in vivo during laser biological tissue soldering

In order to improve the mechanical properties of skin tissue incision, enhance laser absorption efficiency, further shorten healing time and reduce skin fibrosis tendency, this study investigated the effects of CMCS or SWCNT combined with 25 % BSA and 0.4 % ICG on laser tissue welding. Nd:YAG pulsed laser was used for wound closure test on live rats with an energy density of 67.3 J/cm2 and linear scanning of skin incisions. The effects of different types and concentrations of biological dressings on wound closure were tested at different sites. The results showed that biocompatible dressings containing CMCS and SWCNTs had a significant effect in promoting wound healing after laser welding. After laser welding, the tensile strength of the control group without CMCS or SWCNTs was only between 6.5 and 9.8 N/cm2, while that with CMCS reached as high as 26.5 N/cm2. Macroscopic morphology analysis showed that components such as CMCS and SWCNTs could significantly shorten healing time from 14 days to 9–10 days. Optical performance tests demonstrated that a combination of 5 %CMCS and 4 %SWCNTs can significantly increase skin's absorption coefficient for laser photons up to7-8 Lg-1cm−1 and reduce photon diffuse reflectance. HE and Masson staining revealed that when internalized by dressing containing 0.4 %SWCNTs, nanocarbon particles promoted collagen skeleton regeneration but increased fibrosis tendency after 14 days post-laser welding, resulting in unfavorable long-term healing outcomes. However, the combination of CMSC with SWCNTs can significantly improve incision mechanical properties, laser photon absorption rate, and shorten healing time while reducing scar proliferation tendencies.

Effect of silver nanoparticles size on the ultrafast optical nonlinear and optical limiting properties of Nd3+ doped antimony borate glasses

Nd3+ ions containing borate glasses embedded with silver (Ag) nanoparticles (NPs) were prepared by melting and quenching process. Thermal treatment at 450 °C for different holding durations has been performed to tune the size of the NPs embedded in the glass. The influence of growth of NPs on nonlinear optical (NLO) and optical limiting (OL) properties of glasses has been evaluated in the near–infrared spectral provenience under femtosecond pulse regime. The NLO and OL attributes evaluated using Z–scan configuration disclose the enhanced trend of two–photon absorption and nonlinear refraction coefficients and a decrease behaviour of OL threshold with the augment of thermal holding time. This enhancement in NLO coefficients and OL performance with thermal annealing duration is ascribed to the enhancement of the local field with the size of the NPs. The outcomes acknowledge the Nd3+ ions bearing borate glasses embedded with bigger Ag NPs are preferable for nanophotonic applications and optoelectronic functionalities.

A first-principles prediction of the structural, electronic, transport and photocatalytic properties of GaGeX3 (X = S, Se, Te) monolayers.

The discovery of new 2D materials with superior properties motivates scientists to make breakthroughs in various applications. In this study, using calculations based on density functional theory (DFT), we have comprehensively investigated the geometrical characteristics and stability of GaGeX3 monolayers (X = S, Se, or Te), determining their electronic and transport properties, and some essential optical and photocatalytic properties. AIMD simulations show that these materials are highly structurally and thermodynamically stable. Notably, the GaGeSe3 monolayer is a semiconductor with a band gap of 1.9 eV and has a high photon absorption coefficient of up to 1.1 × 105 cm-1 in the visible region. The calculated solar-to-hydrogen conversion efficiency of the GaGeSe3 monolayer is 11.33%, which is relatively high compared to some published 2D materials. Furthermore, the electronic conductivity of the GaGeSe3 monolayer is 790.65 cm2 V-1 s-1. Our findings suggest that the GaGeSe3 monolayer is a new promising catalyst for the solar water-splitting reaction to give hydrogen and a potential new 2D material for electrical devices with high electron mobility.

Design and optimization of the performance of self-powered Sb2S3 photodetector by SCAPS-1D simulation and potential application in imaging

Antimony sulfide (Sb2S3) is considered an excellent semiconductor material for visible light photodetectors (PDs) due to the non-toxicity, stability and high visible photon absorption coefficient. However, the deep physical cascade relationship between Sb2S3 devices and key parameters, such as the thickness, the doping density, the defect density, and the inverse contact of the figure of merit, has not been thoroughly investigated. In order to systematically explore the impact of parameters on Sb2S3 device performance, self-powered optoelectronic devices of TiO2/Sb2S3 p-n heterojunction were simulated by using one-dimensional (SCAPS-1D) software. Base on simulation, we learned that the optimum thickness of Sb2S3 is about 400 nm, the donor and acceptor densities of TiO2 and Sb2S3 layers are 1020 and 1016 cm−3, respectively. In addition, Au was chosen as the back electrode, and the high-quality Sb2S3 functional layer required a defect density of less than 1016 cm−3. Based on the guidance of simulation results, we finally fabricated the FTO/TiO2/Sb2S3/Au self-powered photodetectors. Under an illumination intensity of 3 μW/cm2 at 530 nm, the responsivity (R) and specific detectivity (D*) of the device can be up to 0.357 A/W and 5.1 × 1011 Jones, respectively. Particularly, the device exhibits a fast response with a response time of 1.4 μs and 3 dB bandwidth of 383 kHz. In this regard, we constructed a single-pixel scanning imaging system around the Sb2S3 detector and showed excellent imaging results, which provided a new path for us to develop a new type of visible light detector and imaging system.

ZnSe nanoflakes/ ZnO quantum dots heterojunction-based bandgap engineered, flexible broadband photodetector on paper substrate

ZnO-based photodetectors exhibit high responsivity and high photon absorption coefficients. However, they show absorption in a narrow range and a low photogenerated carrier lifetime, limiting their potential applications in optoelectronics. This work demonstrates a high-performance broadband photodetector using Zinc Selenide nanoflakes (ZnSe) - Zinc Oxide (ZnO) quantum dots (QDs) heterojunction. Using a simple hydrothermal method on a flexible paper substrate, this work overcomes the complexity of previously reported fabrication techniques that involve electrospinning, electron beam lithography, spin coating, etc. Detailed chemical and structural characterization reveal the formation of cubic phase of ZnSe nanoflakes-like structure showing broad absorption in the visible region. In contrast, ZnO QDs show a hexagonal structure and absorption in the ultraviolet region, improving the photodetector's detection range. The device shows superior responsivity (Rʎ) of 17.2 µA/W, and 30 µA/W, with specific detectivity (D*) of 4.74×107 Jones, and 9.39×107 Jones, for ultraviolet, and visible, respectively. Detailed studies based on energy band diagrams are performed to understand the charge transport mechanism. The device shows excellent reliability and high stability for 500 bending cycles, thus, presenting a low-cost, facile approach for developing high-performance photodetectors that find utility in wearables, healthcare, and security/defense applications.

Enhancement of Photocatalytic Activity and Microstructural Growth of Cobalt-Substituted Ba1−xCoxTiO3 {x = 0, …, 1} Heterostructure

The photocatalytic degradation process and absorption kinetics of the aqueous solution of the Cibacron Brilliant Yellow 3G-P dye (Y) were investigated under UV-Vis light. Pure barium titanate BaTiO3 (BT) and cobalt ion-substituted barium Ba1−xCoxTiO3 (x = 0, …, 1) nano-compound powders (BCT) were synthesized using the sol–gel method and colloidal solution destabilization, and utilized as photocatalysts. The powder X-ray diffraction (PXRD) crystal structure analysis of the BT nanoparticles (NPs) revealed a prominent reflection corresponding to the perovskite structure. However, impurities and secondary phase distributions were qualitatively identified in the PXRD patterns for x ≥ 0.2 of cobalt substitution rate. Rietveld refinements of the PXRD data showed that the BCT nano-compound series undergoes a transition from perovskite structure to isomorphous ilmenite-type rhombohedral CoTiO3 (CT) ceramic. The nanoparticles produced displayed robust chemical interactions, according to a Fourier transform infrared spectroscopy (FTIR) analysis. The BT and BCT nanoparticles had secondary hexagonal phases that matched the PXRD results and small aggregated, more spherically shaped particles with sizes ranging from 30 to 114 nm, according to transmission electron microscopy (TEM). Following a thorough evaluation of BCT nano-compounds with (x = 0.6), energy-dispersive X-ray (EDX) compositional elemental analysis revealed random distributions of cobalt ions. Through optical analysis of the photoluminescence spectra (PL), the electronic structure, charge carriers, defects, and energy transfer mechanisms of the compounds were examined. Due to the cobalt ions being present in the BT lattice, the UV-visible absorption spectra of BCT showed a little red-shift in the absorption curves when compared to pure BT samples. The electrical and optical characteristics of materials, such as their photon absorption coefficient, can be gathered from their UV-visible spectra. The photocatalytic reaction is brought about by the electron–hole pairs produced by this absorption. The estimated band gap energies of the examined compounds, which are in the range of 3.79 to 2.89 eV, are intriguing and require more investigation into their potential as UV photocatalysts. These nano-ceramics might be able to handle issues with pollution and impurities, such as the breakdown of organic contaminants and the production of hydrogen from water.

Nonlinear optical properties of gold nanoparticles containing borate glasses at spectral region of surface plasmon resonance

Herein, we subjected the sodium borate glass activated with gold nanoparticles (NPs) to thermal treatment at 500 °C for different holding time to improve their nonlinear optical (NLO) characteristics in visible spectral region. The linear optical density and microscopic measurements confirmed the presence gold NPs in the glass. The outcomes also divulged the growth of Au NPs with an annealing schedule. The NLO attributes were ascertained through the Z–scan method, in which the samples were pumped at 532 nm utilizing nanosecond laser pulses fired at a rate of 1 kHz. Open aperture Z–scan measurements disclosed the existence of two–photon absorption nonlinearity, whereas closed aperture Z–scan experiments revealed the presence of self–defocusing nonlinear refraction in the studied glasses. The measurements unveiled the enhance trend of two–photon absorption and nonlinear refraction coefficients of glass host with thermal holding time owing to the growth of NPs. It was identified that the titled glass embedded with gold NPs annealed for 7 h at 500 °C owes maximum NLO features. Therefore, NBAu–7 glass examined in the current sturdy is beneficial for bio–imaging, optical limiting and NLO nanophotonic applications.

Carbon nanotubes/polyaniline as hydrogen gas sensor: Optical bandgap, micro-morphology, and skin depth studies

In this study, multiwall carbon nanotubes (MWCNTs)/polyaniline nanocomposites deposited on ITO coated glass as substrate by the spin-coating technique were applied to the investigation of the effect of different contents of MWCNTs on the optical and electrical properties of polyaniline. Micrographs from an atomic force microscope were taken to analyze the 3-D microtexture parameters of surface texture factors and fractal dimension. By using optical spectroscopy of samples with different concentrations of MWNCTs in visible and ultraviolet regions, the transmission variations vs photon wavelength, optical bandgap, absorption coefficient, and skin depth were studied. The variation in the resistance of nanocomposite films exposed to 0.4 %vol of H2 gas at room temperature was monitored, and the results indicated that the sensitivity and responsibility of the composites increased with an increase in the MWCNT amount.

Nanoscale-Thick CuPc/β-Ga2O3 p–n Junctions for Harsh-Environment-Resistant Self-Powered Deep-UV Photodetectors

Due to their crucial role in ultraviolet communication and monitoring, deep-ultraviolet (DUV) photodetectors have garnered much interest. Recently, Ga2O3 has emerged as the best material for DUV photodetectors because of its ultrawide bandgap (4.5–4.9 eV), excellent UV photon absorption coefficient, high structural stability, and affordability. However, there are several difficulties in realizing high-performance Ga2O3-based DUV photodetectors with a high tolerance for harsh environments. In this work, nanoscale-thick CuPc/β-Ga2O3 p–n junctions were used to build high-performance DUV photodetectors by a straightforward solution-processing approach. The p–n junction photodetectors exhibit improved photoelectric performance compared to a single device made of β-Ga2O3 or CuPc, with a photo-to-dark current ratio of 3700 and a fast response time of ∼20 ms under a bias of 0 V. Due to the excellent stability of the nanoscale-thick CuPc film, the device can maintain a high photocurrent even at high temperatures or under long-term DUV irradiation. Our work provides an effective strategy toward highly harsh-environment-resistant DUV photodetectors.

NiTe Magnetic Semiconductor Nanorods for Optical Limiting and Hydrogen Peroxide Sensor

The hydrothermal technique was used to make nickel telluride nanorods (NiTe NRs) utilizing ascorbic acid and cetrimonium bromide (CTAB) as reducing agents. Temperature dependent magnetic study for NiTe NRs shows a ferromagnetism behavior. Under 532 nm laser excitation, the obtained materials had a better optical limiting property, with a two photon absorption coefficient of 6.6 × 10− 10 m/W and an optical limiting of 2.44 J/cm2 at 200 µJ. NiTe NRs modified electrode shows a excellent hydrogen peroxide electrocatalytic activity with reproducibility, repeatability and durability. It displays an outstanding sensitivity of 6.35 µAµM− 1 cm− 2 and a detection limit of 6 nM. In the presence of interfering species such as dopamine, uric acid, ascorbic acid, glucose, and folic acid, the electrode has a high level of selectivity. A real sample analysis for NiTe NRs sensor has been established in human serum and rat brain serum showed good recoveries.

Assessment of 3D micro-computed tomography for PV interconnection technology development

X-ray (micro-)computed tomography is a non-destructive characterization method using photons to obtain multiple radiographic projections, which generates a 3D volume rendering of a scanned object after reconstruction. It is recently used in the research and development of photovoltaic modules to investigate smaller volumes in a PV module, for example, detection of cavities in solder joints and visualization of module volumes up to connection ribbon sizes. This work shows that current advanced devices are able to scan larger volumes, using a single-cell 20 × 20 × 0.5 cm 3 module with back-contact multi-ribbon interconnection technology as an example. The generated 3D volume renderings show the interconnection structures and give information on ribbon-metallization interconnections. Next to this, also the solder reflow volume is visible, indicating that the technology has great potential to be used in further interconnection technology development. Finally, a destructive cross section analysis using scanning electron microscopy is performed; it has a higher resolution and can differentiate elements with similar photon absorption coefficients, thus enabling microstructure and intermetallic compound analysis. The findings show the potential for micro-computed tomography as a non-destructive and relatively fast visualization method and how it can give complementary information to other characterization techniques for photovoltaic interconnection research. • X-ray computed tomography is a non-destructive visual inspection technique. • Scanning electron microscopy and x-ray tomography are complementary. • X-ray tomography can aid PV interconnection technology developments.

Effect of Pr6O11 on improving the Near–Infrared nonlinear optical characteristics of zinc borate glasses

For achieving superior nonlinear optical (NLO) features of glass samples, we have incorporated rare earth oxide (in this case, it is Pr6O11) in the composition. The NLO properties are rare earth ions concentration–dependent and, therefore, it is crucial to examine the concentration impact on the NLO attributes of glasses. The effectiveness of Pr6O11 concentration on NLO characteristics of the borate–based glass specimens in the near–infrared region in the femtosecond regime is being investigated in the current work using the Z–scan method. The two–photon absorption coefficients were almost constant up to 0.5 mol % of Pr6O11 and then showed increased behaviour. The nonlinear index of refraction magnitudes was improved with Pr6O11 content in the glass compositions. However, the optical limiting thresholds were found to be decreased with Pr6O11 quantity in the glass compositions. These increases in NLO features and optical limiting efficiencies are attributed to the non–bridging oxygens, polarizability and molar refractions of the glasses. The outcomes of Z‒scan characterization unveil that the high Pr6O11 glass specimens are favourable for the production of NLO devices and optical limiters to execute the functioning in the near–infrared region.

Two Photon Absorption Properties of CBHB and DEABHB Single Crystals for Optical Limiting Applications.

Novel materials of (E)-N'-(4-chlorobenzylidene)-4-hydroxybenzohydrazide (CBHB) and (E)-N'-(4-(diethylamino) benzylidene)-4-hydroxybenzohydrazide (DEABHB) were synthesized by condensation reaction process and solvent evaporation method was employed to grow CBHB and DEABHB single crystals at room temperature. Lattice parameters of CBHB and DEABHB compounds were recorded using single crystal X-ray diffraction method. The presence of functional groups of the synthesized CBHB and DEABHB compounds were confirmed by Fourier transform infrared and Fourier transform Raman spectral analyses. Various intermolecular interactions were studied using Hirshfeld surface analysis. Thermal stability of the hydrazone Schiff base compounds CBHB and DEABHB were studied by thermogravimetric and differential thermal analyses. Third order nonlinear optical properties of CBHB and DEABHB were measured using open aperature Z scan technique. Two photon absorption coefficient and optical limiting properties of the crystals were reported from the Z scan studies.

Unified theoretical description of out-of-equilibrium electron intraband dynamics in gold induced by femtosecond laser pulses

The modeling of the intraband dynamics of conduction electrons in gold induced by a femtosecond laser pulse is addressed. Current approaches, based on the numerical resolution of the Boltzmann equation, are only able to describe electron excitation $\mathit{or}$ relaxation processes. In the present paper, within a single formalism, our kinetic model accounts quantitatively for both excitation and relaxation processes, i.e., photon absorption, thermal conductivity, and electron-phonon coupling coefficient. We suggest that such an approach can only be built by including Umklapp processes in the description of electron collisions. In addition to normal electronic collisional processes with phonons and other electrons, the present theoretical description further includes these mechanisms: (i) a conduction electron can be scattered in the second Brillouin zone after a collision, contributing significantly to the photon absorption, and (ii) the influence of the discrete and periodic nature of the lattice on electron collisions is considered, enabling in particular the coupling between electron and transverse phonons. A good agreement of predictions of this unified modeling with experimental observations for absorption and energy transfer from electrons to the lattice is obtained. We have investigated the influence of the Umklapp processes on the imaginary part of the dielectric function, the electron-phonon coupling parameter, and the transient shape of the electron energy distribution.

Impact of morphology on the nonlinear optical absorption of pristine molybdenum disulfide (MoS2) nanostructures

Tuning of nonlinear absorption and optical limiting action of MoS2 with different morphologies was demonstrated by open aperture Z-scan technique under Nd: YAG laser (532 nm, 7 ns, 10 Hz, 1–5 GW/cm2) excitation. The morphology of pristine MoS2 prepared by hydrothermal method at various reaction times gets altered from nanoclusters (24 h) to nanoplatelets (36 h) and further to nanosheets (48 and 60 h). Earlier XRD confirms the formation of honeycomb lattice of hexagonal crystal phase MoS2 (2H) and Raman ascertains the arrangement of S–Mo–S as a multilayer system. Because of alteration of band structure with morphology, hyper and hypochromic effect occurred in the absorbance of MoS2 nanoparticles. Photoluminescence spectra of MoS2 nanoparticles show two excitonic prominent peaks at 624 nm and 540 nm. All MoS2 nanoparticles prepared at varying reaction time exhibits reverse saturable absorption (RSA) pattern ascribed to two photon absorption process. Among the samples, variation in two photon absorption coefficients with different on-axis peak intensities shows zero slope value for MoS2 nanoclusters (24 h) and thus it exhibits genuine 2 PA. While non-zero slope value of MoS2 nanoplatelets (36 h) and nanosheets (48 and 60 h) display sequential 2 PA mechanism. MoS2 nanoplatelet possess high nonlinear absorption coefficient (5.9 × 10−10 m/W) with a low onset optical limiting threshold (0.73 × 1012 W/m2), which suggests its superiority for developing nonlinear absorption induced optical limiting devices.

Third-order nonlinear optical properties of Sm2O3 activated cadmium alkali borate glasses

Efficacy of tri‒valent samarium ions concentration on the optical and third‒order nonlinear optical (NLO) properties of multicomponent cadmium alkali borate‒based glasses prepared by standard melting‒quenching method has been investigated in this work. The optical properties of cadmium alkali borate glass activated by rare-earth oxide (i.e., Sm2O3) were carried out by using UV–Visible absorption spectroscopy at room temperature. Optical absorption peaks were obtained around 402 nm, 1076 nm, and 1078 nm wavelength. The Fourier transform infrared spectroscopy results revealed the existence of distinct borate units, in the structure of glasses used in the investigation. Z‒scan experiments in the near‒infrared (NIR) spectral regions utilizing the femtosecond (fs) laser pulses were used in order to evaluate the NLO parameters. The two‒photon absorption coefficient and the index of nonlinear refraction values improved significantly for 2 mol% of Sm2O3. This endorses 2 mol% of Sm2O3 encompassed glasses are beneficial for constructing the NLO devices assigned to perform in the NIR region.

The effect of modulation frequency for frequency domain diffuse optic tomography (FDDOT)

In this study, it was illustrated that extremely high frequency (EHF) Ka-band (26.5–40 GHz) modulated frequency domain diffuse optic tomography biomedical optic imaging modality is superior to the generally accepted 100 MHz modulation frequency case. The effect of modulation frequency was shown with reconstructed images for two different modulation frequency simulation cases. Ka EHF-band frequency range covers 26.5–40 GHz. In this simulation study 33 GHz modulation frequency was selected. Forward model problem photon fluencies were generated for 30 equally separated sequential phase delays. Each phase delay has different photon fluence distributions inside the imaging geometry. 3.1 cm grid sizes were set in the x, y, z cartesian grid coordinate system with 31 × 31 × 31 xyz grid elements. To test the advantage of EHF-band modulation frequecy, inverse problem solution algorithm was done and inclusion images were reconstructed for each modulation frequency simulation case. Original inclusion was embedded inside the imaging geometry at (15–16, 15–16, 15–16) x, y, z coordinate system in the three-dimensional (3D) cubic spatial form. Homogeneuous tissue background photon absorption, scattering, and anisotropy coefficients were selected as µa = 0.1 cm−1, µs = 100 cm−1, and g = 0.9. Four sources and four detectors were placed on the back-reflection geometry. Forward model problem was built between sources, voxels, and detectors. Forward model problem photon fluencies were generated based on the diffusion equation approximation of the radiative transport equation formula in the frequency domain. Original inclusion was reconstructed by simply applying mathematical pseudoinverse problem solution function. It was observed that, reconstructed inclusion image at the 33 GHz Ka-band modulation frequency simulation case is superior to the reconstructed inclusion image at the 100 MHz modulation frequency simualtion case. Since there are too many frequency selection opportunities, the best Ka-band frequency was selected to demonstrate here. Thus, 33 GHz and 100 MHz modulation frequencies were tested against each other. These two different electronic modulation frequencies were tested and compared with each other.

Nanosecond nonlinear optical, optical limiting and structural properties of Eu3+ activated antimony sodium borate glasses embedded with silver nanoparticles: Effect of heat treatment

Effect of heat treatment on nonlinear optical and optical limiting features of borate based glasses has been ascertained by the Z‒scan technique and the results are discussed in detail. The electron microscopic measurements confirmed the existence of spherical shaped Ag nanoparticles and their growth with heat treatment. The values of the two photon absorption coefficient (α2), nonlinear refractive index (n2) and third‒order nonlinear susceptibility (χ(3)) showed an increase trend with the increase of the heat treatment duration up to 50 h. Subsequently, the nonlinear optical magnitudes decreased at higher heat treatment durations (for 72 h). The enhancement in the nonlinear optical results of the glasses was attributed to the local field stimulated by silver nanoparticles in the vicinity of the Eu3+ ions in the glass matrices. The optical limiting threshold values demonstrated an opposite trend to that of α2. The enhancement in α2 from 2.84 × 10−11 to 4.66 × 10−11 mW−1 and decrement in optical limiting threshold values from 2.85 × 108 to 1.73 × 108 Jcm−2 with variation of heat treatment durations from 0 to 50 h suggest the SNBEuAg0.8‒50 glass is beneficial for designing the photonic limiters to work in the visible region to suppress the high energy laser radiations.

Electronic and optical properties of CsGeX[formula omitted]M (X ,M = Br, Cl, I) perovskites for solar cell applications: First-principles study using PBE and TB-mBJ potentials

The effect of mixed halogen composition on the structural, electronic, and optical properties of CsGeX2M (X, M=Cl, Br, I) has been studied using density functional theory, generalized gradient approximation, and modified Becke–Johnson exchange potential (TB-mBJ). The electronic properties show that all structures are direct semiconductors with wide band gaps between 1.251 eV and 1.655 eV. In addition, the band gap values of these materials are tuned by decreasing the number of chlorine or bromine atoms. PDOS analysis of CsGeX2M compounds shows that the Cs atom has negligible effects on the electronic bands of these perovskites. The major contribution to the electronic bands of these compounds close to Ef comes from the Ge orbitals and I, Br, and Cl . Optical properties show that these materials have good absorption capacity. The photon absorption coefficient along the z-axis in the visible light region is between 40 × 104 cm−1 and 65 × 104 cm−1, thanks to their narrow band gap. Furthermore, the real ɛ1 and imaginary ɛ2 parts of their dielectric functions show that CsGeBr2I, CsGeBr2Cl, CsGeCl2I, and CsGeCl2Br also possess a high ability to retain the energy they absorb.