Photon Absorption Research Articles

Keldysh crossover in one-dimensional Mott insulators

Recent advancements in pulse laser technology have facilitated the exploration of nonequilibrium spectroscopy of electronic states in the presence of strong electric fields across a broad range of photon energies. The Keldysh crossover serves as an indicator that distinguishes between excitations resulting from photon absorption triggered by near-infrared multicycle pulses and those arising from quantum tunneling induced by terahertz pulses. Using a time-dependent density-matrix renormalization group, we investigate the emergence of the Keldysh crossover in a one-dimensional (1D) Mott insulator. We find that the Drude weight is proportional to photo-doped doublon density when a pump pulse induces photon absorption. In contrast, the Drude weight is suppressed when a terahertz pulse introduces doublons and holons via quantum tunneling. The suppressed Drude weight accompanies glassy dynamics with suppressed diffusion, which is a consequence of strong correlations and exhibits finite polarization decaying slowly after pulse irradiation. In the quantum tunneling region, entanglement entropy slowly grows logarithmically. These contrasting behaviors between the photon-absorption and quantum tunneling regions are a manifestation of the Keldysh crossover in 1D Mott insulators and provide a novel methodology for designing the localization and symmetry of electronic states called subcycle-pulse engineering.

Influence of Magnesium Doping Concentrations and annealing on the Transmittance and Energy Band-gap of Sb2S3 Thin Films Deposited via Chemical Bath Deposition Technique

The incorporation of thin film materials into a wide range of technological applications has attracted considerable interest owing to their distinct properties and versatile functionalities. In this study, Magnesium alloyed and Antimony sulphide (Sb2S3) thin films were successfully deposited on glass substrates by chemical bath deposition technique. The films were grown at room temperature of constant pH. The concentrations of magnesium varied between 0.1M and 0.3M. The films were annealed at annealing temperature between 100˚C and 300˚C at a fixed annealing time of 1 hour. The films were characterized using UV-spectrophotometer to investigate the variation of optical and solid state properties with wavelength in the UV-VIS-NIR region. The result showed that the presence of the alloying agent and annealing treatments modified the optical and solid state properties of the films significantly. The transmittance of the films was high. Annealing led to reduced transmittance due to increased crystallite size, notably in films doped with 0.1M Mg2+ ions and annealed at 200˚C, suggesting enhanced photon absorption. The energy band gaps were found to be direct and in the range of 1.25 eV to 1.72 eV for the as grown films and 1.15eV to 1.3eV for the films annealed at annealing temperatures 300˚C. The study identifies a direct correlation between magnesium doping concentration, annealing conditions, and shifts in the energy band-gap of the films. The values of the energy band gaps are all within the range suitable for use of the layers as absorbers in hetero-junction solar cell devices for sustainable energy applications.

Surfaces properties correlation with optical parameters of thickness dependent self-affine nanostructured SnS thin films: A study based on scaling law

Fractal concepts are employed to investigate the surface properties of tin sulfide (SnS) thin films, which are deposited on Fluorine-doped tin oxide (FTO)- coated glass substrates by the thermal evaporation (TE) technique. The surface topography of each deposited film is captured by AFM. The fractal dimensions of the AFM image were extracted through the Higuchi algorithm, and it is found that the thinner sample surface exhibits the maximum fractal dimension. The autocorrelation function and height-height correlation function are used to investigate the self-affinity behavior of surfaces. Dynamic surface roughening is characterized by different scaling exponents, such as the roughness exponent, the growth exponent, the dynamic scaling exponent, and the steepening exponent. It was observed that the values of average roughness, interface width, lateral correlation length, and mean square local slope are strongly influenced by film thickness. The self-affine fractal nature of thin film is estimated by the roughness exponent; however, island- or mound-type growth with quick surface roughening behavior is predicted by the growth exponent and the dynamic scaling exponent. Further, we have tried to correlate the optical properties such as transmission, reflection, and refractive index with the fractal dimension of SnS thin film. The increase in optical reflection with decreasing roughness indicates that absorber surfaces of the best crystalline films have the lowest reflectivity. The present results suggest that such surfaces, having a maximum fractal dimension and minimum optical reflectance, can be used as photon absorber layers for advanced solar cell devices.

Precise control of hole transport layer integration on PDTS-DTTFBT: PC71BM organic solar cells

Efforts to enhance the commercial viability of organic solar cells (OSCs) prioritize high power conversion efficiency(PCE). This study proposes precision tuning of the photoactive layer thickness in the nanoscale as an innovative method to boost efficiency. Utilizing PDTS-DTTFBT: PC71BM, an organic blend, as the active layer aims to capture a broad photon range while addressing optical losses due to low-energy photons rather than mere absorption. The study integrates PEDOT: PSS and molybdenum trioxide (MoO3) as hole transport layers, alongside C60, PC60BM, and ZnO electron transport layers. Meticulous analysis of their photon absorption, reflectance, charge carrier generation, and localized energy variance emphasizes their impact on the efficiency of PDTS-DTFFBT: PC71BM active films. Notably, incorporating MoO3 as the hole transport layer significantly mitigated losses and altered localized energy, culminating in an impressive 17.69% efficiency at an optimized blend thickness of 120 nm. Augmenting blend thickness directly boosts PCE and current density until reaching optimal thickness, while diminishing fill factor, with minimal effect on open-circuit voltage. These results highlight the efficacy of this methodology in enhancing the performance of organic solar cells.

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.

Electrical, optical and mechanical properties of monolayer MoTe2 for applications in wearable optoelectronic devices

Transition metal dichalcogenides (TMDs) have excellent optical and mechanical properties and have potential application value in wearable optoelectronic response devices. MoTe2, a representative material of TMDs, is studied by first-principles calculation in this paper. The results show that the MoTe2 monolayer has a direct band gap of 1.110eV, which has a strong light absorption capacity and can produce a high concentration of photogenerated charge carriers after light absorption. The material is soft and exhibits the unique mechanical properties of layered materials. The effects of biaxial strain and defects on the properties of the materials were analyzed. The results show that the biaxial compression strain can enhance the light absorption curve of the material, enhance the light absorption of the photogenerated carrier, and expand the range of its energy distribution. The tensile strain decreases the value of the photon absorption curve and decreases the range of energy distribution of photogenerated carriers. The Mo vacancy defect increases the absorption curve value in the low energy region and broadens the optical response range of the material. The two types of vacancy defects both induce a ‘discrete’ distribution of photogenerated carriers. The Mo vacancy significantly affects the elastic modulus and anisotropy properties of the material, resulting in the material changing from ductile to brittle. When Mo vacancy is added, the spatial distribution of the elastic modulus of the material also changes greatly. Therefore, MoTe2 has potential application in flexible optoelectronic devices, and its performance can be controlled by strains and defects.

Optical switch based on tunable perfect photon absorption

We investigate the manipulation of optical field within quantum electrodynamics (QED) scheme. In our proposal, the cold three-level atoms interact with a two-sided cavity driven by two coherent beams with a relative phase. Coherent perfect absorption (CPA) appears when the beams are in phase. However, the perfect outputs occur when the beams are out of phase. On the basis of the phase modulation, an optical switch can be operated at a high efficiency. With a coherent control laser, the excited and metastable levels of the atoms are coupled. Electromagnetically induced transparency (EIT) is produced at two-photon resonance, which leads to four-band CPA. By virtue of the control laser, the switching efficiency can be maximized in a weaker probe field, which provides advantages over two-level atoms on weak-signal switching.

Amphi-Luminescent MoS2 nanostructure for photocatalytic splitting of water and removal of Methylene Blue

Chemical dyes used in the textile industries are one of the major pollutants in water. Methylene blue (MB) is a commonly seen dye that creates hazardous health problems. In this article the photocatalytic degradation of MB by the nanocatalyst MoS2 (Nano-MoS2) and carbon dot (C Dots) incorporated MoS2 (Nano-CD-MoS2) is reported. The photocatalytic degradation of MB is analyzed based on the electron-hole recombination rate of the catalyst. Photoluminescence emission exhibited by the catalyst is used as a key indicator to probe the electron-hole recombination rate. Nano-MoS2 was synthesized hydrothermally at 180 0C for 8 h from ammonium tetra thiomolybdate (ATTM). C Dot was prepared following a green root from ash guard extract which later mixed with Nano-MoS2 and kept in an autoclave at a temperature 140 °C for 4 h to get Nano-CD-MoS2. The photoluminescence (PL) and photocatalytic behavior of Nano-MoS2 and Nano-CD-MoS2 and their application for water splitting and water purification are reported. The incorporation of graphene and artificial C Dot into MoS2 nanostructures are reported to increase the conductivity and active edge sites of MoS2 that enhances the photocatalytic action. Since green C Dots are eco-friendly and easily synthesizable than artificial C Dots, as a novel study, this article investigated the influence of green C Dots on the PL and photocatalytic performance of nanosized MoS2. Nano-MoS2 and Nano-CD-MoS2 exhibited both upconversion and downconversion PL; accordingly the nanostructures were termed as amphi-luminescent. The amphi-luminescence property widens the photon absorption range and hence enhances the catalytic degradation of dyes. Nano-MoS2 which exhibited lesser intensity of amphi-luminescence emission compared to Nano-CD-MoS2 showed better results in degradation of MB. C Dots may bind with the valence band electrons of MoS2, resulting in the reduction of dangling bonds. Dangling bonds can trap photo-induced excitons to hinder the rate of electron-hole recombination. So, fast electron-hole recombination occurs in Nano-CD-MoS2 than Nano-MoS2. Fast electron-hole recombination supports radiative electron-hole recombination while suppresses the non-radiative energy transfer of electrons and causes high PL intensity. However, according to the energy level diagram, Nano-MoS2 with minimal electron-hole recombination rate is more favorable for O2/O2–,.OH/ OH– and.OH/H2O reactions that facilitate MB degradation. Photocatalytic activity of catalysts were confirmed by measuring the photocurrent from a simple custom-made two-electrode water photolysis cell where the nanocatalysts were dispersed in electrolyte. Lead and steel rods were used as electrodes. Multimeter was used to measure current. Nano-MoS2 exhibited better performance with a maximum photocurrent of 141 µA. Influence of green C Dots in energy levels, PL and photocatalysis of MoS2 and mechanisms of PL and degradation of MB are thoroughly investigated in this article.

Study of Laser-Induced Multi-Exciton Generation and Dynamics by Multi-Photon Absorption in CdSe Quantum Dots.

Multi-exciton generation by multi-photon absorption under low-energy photons can be thought a reasonable method to reduce the risk of optical damage, especially in photoelectric quantum dot (QD) devices. The lifetime of the multi-exciton state plays a key role in the utilization of photon-induced carriers, which depends on the dynamics of the exciton generation process in materials. In this paper, the exciton generation dynamics of the photon absorption under low-frequency light in CdSe QDs are successfully detected and studied by the temporal resolution transient absorption (TA) spectroscopy method. Since the cooling time of hot excitons extends while the rate of auger recombination is accelerated when incident energy is increased, the filling time of defect states is irregular, and exciton generation experiences a transition from single-photon absorption to multi-photon absorption. This result shows how to change the excitation. Optical parameters can prolong the lifetime of excitons, thus fully extracting excitons and improving the photoelectric conversion efficiency of QD optoelectronic devices, which provides theoretical and experimental support for the development of QD optoelectronic devices.

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.

Exploring the potential of phosphorescence for mitigating urban overheating: First time representation in an Urban Canopy Model

Phosphorescence (PP) has emerged as a promising passive cooling solution for the built environment, characterized by its ability to emit radiation persistently after photon absorption, thereby enhancing the solar radiation rejection capability and effective albedo of the surface. While various compounds have shown excellent properties for energy-saving purposes, assessing their benefits for the built environment towards their actual implementation still remains a challenge. To bridge the gap between laboratory-scale characterizations and real-world applications, this study employs the Princeton Urban Canopy Model (PUCM) to assess the surface cooling potential of PP coatings. This research represents the first numerical modeling of phosphorescence, extrapolating findings from experimentally validated parameters to conditions and scale of real cities. Results demonstrate the substantial capacity of PP to ameliorate surface overheating in urban areas, potentially reducing surface temperatures by up to −2.6 °C when optimized. Additionally, material optimization emerges as a crucial factor for exploiting the potential of phosphorescence in mitigating urban overheating, highlighting its strategic relevance for the urban canopy environment.

Color Tuning in Bovine Rhodopsin through Polarizable Embedding.

Bovine rhodopsin is among the most studied proteins in the rhodopsin family. Its primary activation mechanism is the photoisomerization of 11-cis retinal, triggered by the absorption of a UV-visible photon. Different mutants of the same rhodopsin show different absorption wavelengths due to the influence of the specific amino acid residues forming the cavity in which the retinal chromophore is embedded, and rhodopsins activated at different wavelengths are, for example, exploited in the field of optogenetics. In this letter, we present a procedure for systematically investigating color tuning in models of bovine rhodopsin and a set of its mutants embedded in a membrane bilayer. Vertical excitation energy calculations were carried out with the polarizable embedding potential for describing the environment surrounding the chromophore. We show that polarizable embedding outperformed regular electrostatic embedding in determining both the vertical excitation energies and associated oscillator strengths of the systems studied.

Optical Analysis of Perovskite III-V Nanowires Interpenetrated Tandem Solar Cells.

Multi-junction photovoltaics approaches are being explored to mitigate thermalization losses that occur in the absorption of high-energy photons. However, the design of tandem cells faces challenges such as light reflection and parasitic absorption. Nanostructures have emerged as promising solutions due to their anti-reflection properties, which enhances light absorption. III-V nanowires (NWs) solar cells can achieve strong power conversion efficiencies, offering the advantage of potentially integrating tunnel diodes within the same fabrication process. Metal halide perovskites (MHPs) have gained attention for their optoelectronic attributes and cost-effectiveness. Notably, both material classes allow for tunable bandgaps. This study explores the integration of MHPs with III-V NWs solar cells in both two-terminal and three-terminal configurations. Our primary focus lies in the optical analysis of a tandem design using III-V semiconductor nanowire arrays in combination with perovskites, highlighting their potential for tandem applications. The space offered by the compact footprint of NW arrays is used in an interpenetrated tandem structure. We systematically optimize the bottom cell, addressing reflectivity and parasitic absorption, and extend to a full tandem structure, considering experimentally feasible thicknesses. Simulation of a three-terminal structure highlights a potential increase in efficiency, decoupling the operating points of the subcells. The two-terminal analysis underscores the benefits of nanowires in reducing reflection and achieving a higher matched current between the top and the bottom cells. This research provides significant insights into NW tandem solar cell optics, enhancing our understanding of their potential to improve photovoltaic performance.

Thermometries for Single Nanoparticles Heated with Light.

The development of efficient nanoscale photon absorbers, such as plasmonic or high-index dielectric nanostructures, allows the remotely controlled release of heat on the nanoscale using light. These photothermal nanomaterials have found applications in various research and technological fields, ranging from materials science to biology. However, measuring the nanoscale thermal fields remains an open challenge, hindering full comprehension and control of nanoscale photothermal phenomena. Here, we review and discuss existent thermometries suitable for single nanoparticles heated under illumination. These methods are classified in four categories according to the region where they assess temperature: (1) the average temperature within a diffraction-limited volume, (2) the average temperature at the immediate vicinity of the nanoparticle surface, (3) the temperature of the nanoparticle itself, and (4) a map of the temperature around the nanoparticle with nanoscale spatial resolution. In the latter, because it is the most challenging and informative type of method, we also envisage new combinations of technologies that could be helpful in retrieving nanoscale temperature maps. Finally, we analyze and provide examples of strategies to validate the results obtained using different thermometry methods.

Comparative physiological and anatomical responses of Tagetes erecta L. and Zinnia elegans Jacq. seedlings to AgNO3 and ZnSO4 metals and their nanoparticles

Heavy metals (HMs) pose a significant ecological risk due to their enduring presence in the ecosystem. They become more prevalent as a result of urbanization and industrialization, disrupting critical functions of plant life such as photosynthesis, seedling growth, and germination. Understanding the impact of HMs and nanoparticle exposure on plants is crucial for developing effective strategies to mitigate their potential hazards. Therefore, an effort was made to elucidate the impact of biosynthesized Ag NPs (nanoparticles) and ZnO NPs versus their precursor metal salts, AgNO3 and ZnSO4, respectively on two Asteraceous plants, Mexican marigold (Tagetes erecta L.) and Zinnia (Zinnia elegans Jacq.) in hydroponic solution by monitoring the changes in photosynthetic pigments and their associated photochemistry of photosystem II along with the anatomical attributes. In the present study, two concentrations (50 μM and 100 μM) for each treatments viz., AgNO3, Ag NPs, ZnSO4 and ZnO NPs were given to the seedlings. Metal salts were found to be more toxic than their nanoparticles, and this was manifested in terms of reduction in photosynthetic pigments, especially chlorophylla content (by 32% in marigold and 27% in Zinnia upon exposure to 100 µM of AgNO3, respectively) in both test seedlings. Reduction in chlorophyll fluorescence parameters was also found under metal as well as nanoparticle toxicity. In contrast, energy flux parameters such as absorption of photon per active reaction centre (ABS/RC), trapped energy flux per active reaction centre (TR0/RC), electron transport flux per active reaction centre (ET0/RC) and energy dissipation flux per active reaction centre (DI0/RC) increased significantly to cope with stress toxicity. Similarly, metals and nanoparticles also distorted the anatomy of the root and leaf, and the effect was more intense under AgNO3 treatment than with ZnSO4 in Zinnia. In conclusion, Zinnia seedlings were more resilient towards all the tested conditions, which might be attributed to their adaptability to various environmental factors, indicating their potential for thriving in diverse climates.

Chemically derived quinary Cu2Co1–xNaxSnS4 photon absorber material and its photocatalytic application

The solar absorbing materials attract attention for the opto-electronic device applications such as solar cells and photocatalysis. Interest in photocatalytic materials to clean up the wastewater has started to increase. Generally, semiconductors sensitive to UV region are used. However, most of the light from the sun is in the visible region. Cu2CoSnS4 is a promising material that exhibits superior photo-response in the visible regions with an appropriate band gap. In this study, Cu2CoSnS4 films were prepared by the sol–gel method. Cu2Co1–xNaxSnS4 was synthesized for the first time by partly substituting sodium with cobalt. With this approach, noticeable improvements were observed in the physical properties of the material. With the sodium replacement, the Cu2Co1–xNaxSnS4 exhibited high photocatalytic performance toward the degradation of methylene blue (MB) under visible-light irradiation. According to the results, Cu2CoSnS4 and Cu2Co1–xNaxSnS4 samples degraded the MB solution by degradation efficacy values of 89.69% and 94.57%, respectively, in a short time like 40 min under visible light. This study shows that the substitution of sodium boosted the degradation efficiency by 5.4%. For the Cu2CoSnS4 and Cu2Co1–xNaxSnS4 samples, the computed reaction rate constants are 0.059 min−1 and 0.077 min−1, respectively.

A systematic first-principles investigation of the structural, electronic, optical, thermodynamic and transport properties of lead-free pyrochlore oxides Q2Sb2O7 (Q= Be, Ca, Sr) for low-Cost energy applications

A systematic study has been performed on structural, optical and thermophysical properties of newly designed pyrochlore oxides Q2Sb2O7 (Q = Be, Ca, Sr) employing FP-LAPW based first-principles calculations. The GGA approach was used to treat exchange and correlation potentials. The investigated E-V plots reveals that Sr2Sb2O7 is the most stable structure compared to Be2Sb2O7/Ca2Sb2O7. A direct energy bandgap of 0.29 eV is evident from band structure plot of Be2Sb2O7, however, Ca2Sb2O7/Sr2Sb2O7 possess indirect energy bandgaps of magnitude 1.47/1.467 eV. The studied materials show maximum absorption of incoming photons in near UV region as shown in ε2(ω) plots, however, considerable absorption in visible region is also present. Ca2Sb2O7/Sr2Sb2O7 are effective optical material with a n(ω) value between 1.0 and 2.0. Optical properties of pyrochlore oxides reveal that these materials are potential candidates for shielding materials in upper UV region. A photon reflection of up to 60% is evident from the R(ω) in UV region, however, in IR and visible regions, the reflectance is negligible. Based on calculated values of Seebeck coefficient (S), we can state that Be2Sb2O7 is n-type semiconductor whereas Ca2Sb2O7/Sr2Sb2O7 are p-type semiconductors. The most effective thermoelectric material among Q2Sb2O7 (Q = Be, Ca, Sr) is Ca2Sb2O7 as its ZT value is highest (∼1.05) in the entire temperature range. Thermodynamic properties of Q2Sb2O7 (Q = Be, Ca, Sr) are also evaluated to check dynamical stability and appropriateness of these materials in thermal applications. The investigated outcomes show that these pyrochlore oxides are potential candidates for thermoelectric and optoelectronic device applications.

Solar Hydrogen Production by Artificial Photosynthesis in Photoreactor for Sustainable Mobility

The thermo-industrial human society is mainly based on fuels. Currently, societies are fully dependent on fossil fuels which cause climate change that threaten human race. Solar fuels are well suited technologies to face these challenges. Long-term solar energy storage based on chemical fuel production from water (and potentially CO2) has a significant importance to decarbonize our societies. Artificial photosynthesis is especially adapted to produce solar fuels, such as hydrogen, methane, ethanol, etc. This study focuses on hydrogen production. Water splitting with photolysis reaction is possible thanks to photocatalysts that absorb light and produce hydrogen. Modeling the hydrogen production is based on 3 main physics fields because the process is limited and controlled by radiative transfer. Electromagnetism is used to determine radiative properties. Then, radiative transfer allows to calculate photon absorption rates. Finally, the thermokinetic coupling law establishes a relation between photon absorption rate and hydrogen production rate. Experimentally, hydrogen production is operated in a dedi-cated laboratory-scale benchmark photoreactor. Photon flux density is controlled by a LED panel and hydrogen pressure variation is monitored with a pressure sensor. It is then possible to calculate experimental hydrogen production rates. The model predicts a non-linear thermo-kinetic coupling law, which fits well experimental results. Consequently, we demonstrated that the concept of incident solar flux density dilution is an important feature for process optimiza-tion. Several dilution technologies from TRL 3 to 5 are implemented in our laboratory thanks to the new PAVIN solar platform. They aim to validate high-efficiency technologies thanks to solar flux dilution.

Silver molybdate: an excellent optical limiting material under nanoregime for photonic device application

There is a mounting demand for nonlinear optical materials with superior optical limiting performance which has a noticeable impact on protecting the delicate optical components from laser-induced damage. Transition metal molybdates have garnered attention in the nonlinear optics field due to their outstanding optical and luminescent properties, which give rise to widespread applications in next-generation optoelectronics devices. The structural confirmation of the as prepared silver molybdate nanoparticles were made by XRD and Raman spectroscopy analysis. The linear optical properties and the band gap of the synthesized material were studied using UV–Visible and photoluminescence spectroscopy. SEM analysis revealed the pebble like morphology of the silver molybdate nanostructures. The nonlinear responses of the samples were studied using open aperture z-scan approach with Nd:YAG pulsed laser (532 nm, 9 ns, 10 Hz). The sample exhibits reverse saturable absorption pattern attributed to the two photon absorption (2PA) mechanism. The obtained OL threshold value is in the order of 1012 which is suitable for fabricating optical limiters in nano second pulsed laser regime.

Optimization of preparation conditions by response surface methodology for synthesis of titanium dioxide/reduced graphene oxide composite in dye-sensitized solar cells

This study aimed to address the need for alternative materials in the anode layer to enhance the performance of dye-sensitized solar cells (DSSCs). The synthesis of titanium dioxide/reduced graphene oxide (TiO2/rGO) was carried out using the response surface methodology by face central composite design (RSM/FCC). This method allowed us to systematically evaluate the influence of two key factors, namely the weight percentage of precursor graphene oxide (GO wt%) and the L-ascorbic acid ratio, | on the power conversion efficiency (PCE) of DSSCs. Our research is significant because it explores the synthesis of TiO2/rGO as a novel material for the anode layer in DSSCs. This material holds promise for improving device performance due to its unique properties, such as enhanced charge transport and light harvesting capabilities. Additionally, TiO2/rGO can serve multiple functions within the DSSCs device, acting not only as a charge transport layer but also potentially as a light scattering layer to increase photon absorption. The statistical analysis revealed that the GO wt% had a more significant influence on PCE compared to the L-ascorbic acid ratio. Furthermore, our simulation results demonstrated high validity and accuracy, with a correlation coefficient (R2) of 0.9988 and a residual standard error of less than 5 %. The optimized DSSCs-based TiO2/rGO anode achieved a remarkable PCE of 7.12 %, representing a 29 % improvement compared to the pure TiO2-based DSSCs anode. In summary, our study highlights the importance of synthesizing TiO2/rGO as a novel material for the anode layer in DSSCs and demonstrates its potential for significantly enhancing device performance. This study emphasizes these key points more prominently in the abstract to better convey the novelty and significance of our findings.