Lead-free perovskite solar cells offer a sustainable pathway for next-generation photovoltaics. This study employs a combined Density Functional Theory (DFT) and SCAPS-1D approach to investigate the structural, electronic, optical, and photovoltaic properties of pristine and Al/In-doped CsSnI3. Using the Quantum ESPRESSO package with PBE-GGA, DFT calculations reveal that 3.7% Al3＋ or In3+ doping enhances the structural stability of CsSnI3, with In-doped systems exhibiting optimal Goldschmidt tolerance (t=0.86) and octahedral factors (μ=0.53). The direct bandgap increases from 0.46 eV (pristine) to 1.23 eV (Al-doped) and 1.65 eV (In-doped), with a Fermi level shift promoting p-type conductivity and introducing localized states near band edges. Optical properties calculations indicate strong sub-gap absorption and free-carrier effects in the doped systems, manifested as dramatically enhanced low-energy extinction coefficient, absorption coefficient, and reflectivity, together with increased static dielectric constant and refractive index due to intraband contributions from p-type doping at the Sn site. SCAPS-1D simulations, conducted for pristine CsSnI3 under AM1.5G illumination, evaluate three device configurations (e.g., FTO/PCBM/CsSnI3/Cu2O/Au), achieving power conversion efficiencies up to 27.96% at an optimal absorber thickness of 1100–1200 nm. These results underscore the potential of Al and In doping to enhance CsSnI3 stability and optoelectronic properties, while the SCAPS-1D analysis provides a robust framework for optimizing pristine CsSnI3-based solar cells, paving the way for efficient, eco-friendly photovoltaic technologies.

The Weyl semimetal NbP exhibits remarkable electronic properties arising from its nontrivial topology and symmetry-protected nodes. Here, we explore how tensile strain and external electric fields can modulate its electronic bands and topological characteristics using first-principles density functional theory combined with model Hamiltonian approaches. All calculations are performed within the plane-wave pseudopotential framework, including spin-orbit coupling, and maximally localized Wannier functions are employed to analyze the Berry curvature, Fermi arcs, and node evolution. Under a 4% tensile strain, NbP develops a small band gap of ∼0.05 eV along the Γ-Σ direction, accompanied by a reduction in carrier density near the Fermi energy. Increasing strain to 8% leads to a gap of ∼0.035 eV and further suppression of Fermi-level states, indicating strain-driven band reorganization. The application of electric fields produces minute but significant effects: at 0.51 V Å-1, band curvature shifts slightly, while at 1.29 V Å-1, a gap of ∼0.02 eV opens along the Γ-Spath. This controlled gap opening signifies a transition toward switchable electronic phases, highlighting NbP's potential in topological electronics and field-tunable quantum devices.

In this study, we conduct a detailed first-principles investigation of the structural, electronic, optical properties, thermodynamic and mechanical stability of K _3 GaX _6 (where X = Cl, Br, I) for optoelectronic applications. This investigation is carried out using density functional theory (DFT) within the Quantum ESPRESSO framework, applying the generalized gradient approximation with the Perdew–Burke–Ernzerhof functional. The structural properties were studied by full geometry optimization and the stable lattice parameters were obtained for all the compounds. The charge density distribution shows a strong ionic character and is significantly localized around halide ions, which confirms the bonding nature within the [GaX _6 ] octahedral units. The calculated negative formation energies and elastic constants satisfying the Born criteria indicate that the investigated compounds are thermodynamically favorable and mechanically stable. For the electronic properties, the band gap of K _3 GaCl _6 , K _3 GaBr _6 and K _3 GaI _6 were calculated. A similar decreasing trend is observed in the optical properties such as absorption coefficient, optical conductivity and plasmonic response from Cl to Br to I. In contrast, the reflectivity is almost invariant over the series, suggesting similar surface interaction behavior despite the compositional variation. The projected density of states reveals that the valence band maximum is predominantly derived from the halogen p orbitals, while the conduction band minimum is mainly composed of Ga s and Ga p orbitals. The Ga-3d states are located at lower energies and do not contribute significantly to the electronic states near the Fermi level. Among the compounds studied, the calculated band-gap values show that the K _3 GaX _6 (X = Cl, Br and I) compounds are promising for optoelectronic applications in different spectral regions. K _3 GaI _6 with a narrow direct band gap of 0.80 eV is promising for near-infrared (NIR) applications, such as infrared photodetectors and NIR optoelectronic devices. K _3 GaBr _6 has an intermediate direct band gap of 2.05 eV, which is in the visible spectral range, and thus, it is a promising candidate for visible-light optoelectronic devices, such as photodetectors, light-emitting devices and optical sensors. On the other hand, K _3 GaCl _6 has a large direct band gap of 3.32 eV, suggesting that it can be a good candidate for ultraviolet (UV) and near-UV optoelectronic applications such as UV photodetectors, optical coatings and ultraviolet filtering devices.

The focus of this research is the development of a sustainable nanofertilizer synthesized from zeolite nanostructures derived from industrial sludge with bovine-enriched nitrogen, phosphorus, and potassium (NPK) nutrients. By reusing organic and industrial byproducts, this formulation is intended to maintain or potentially increase nutrient efficiency while reducing the environmental impact. Zeolite nanostructures were synthesized by the sol-gel method and were subsequently mixed with bovine bone and blood powder to improve the nutrient content. X-ray diffraction (XRD) confirmed pure zeolitic crystalline phases, while elemental composition studies through X-ray fluorescence analysis (XRF) demonstrated high levels of Si, Al, Ca, P, K, and N species, indicating successful incorporation of nutrients and as well determining the concentration of trace elements, which is below the USEPA standard. Fourier transform infrared spectroscopy (FTIR) analysis revealed distinct bands, as seen at 3277, 1638, 1036, and 565-467 cm-1, supportive evidence of hydroxyl, phosphate, and aluminosilicate groups. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses both indicated pores and irregular shapes of particles, which contributed to an increased surface area and possible retention of nutrients. The nanofertilizer developed was used again to evaluate its impact on maize (Zea mays L.) production relative to control (no fertilizer) and conventional fertilizer treatment. It assessed phenology, growth, and yield. Nanofertilizer treatment has greater grain yield components (8.10 t/ha) when compared with conventional ones (7.84 t/ha).This result provides evidence for the zeolite-based nanofertilizer being a sustainable, effective choice for increasing maize productivity that contributes to circular economy in agriculture.

Transition-metal doping in semiconductors is a promising strategy to obtain magnetic and semiconducting properties in a single crystal and to enhance ferromagnetic (Fm) transition temperature (TC) above room temperature, which is necessary for spintronic applications. It induces changes in bond lengths upon relaxation and introduces new electronic states in the band structure, which modify the band gap and potentially give rise to half-metallic behavior. To this end, density functional theory (DFT) calculations using the GGA-PBE functional, including Hubbard U corrections (PBE+U), were performed to investigate the electronic structure, magnetic properties, and orbital-resolved spin polarization of the dopant 3d states in Cr- and Mn-doped AlP compounds. The double substitution of Mn or Cr at next-nearest neighbor (NN) sites results in strong FM interactions, with an increased TC to 671 K for Mn and 897 K for Cr according to Hubbard U correction. Analyses of the band structure and projected density of states (PDOS) indicate that the NN configurations exhibit robust half-metallicity in both the PBE and PBE+U calculations, with stronger spin polarization of the d-orbital components of the dopants under the U correction. These findings indicate that Cr- or Mn-doped AlP shows great promise for future spintronic applications.

Topological materials host electronic states that remain robust against perturbations and offer promising routes toward quantum functional devices. In this study, we employ first-principles calculations and model Hamiltonian analyses to investigate how external stimuli, namely tensile strain and electric fields, tune the electronic and topological characteristics of SrSi2 and CoSi. Density functional theory (DFT) calculations are performed using the plane-wave pseudopotential with spin orbit coupling (SOC) included, capturing relativistic effects. Maximally localized Wannier functions are generated with Wannier90 to construct tight-binding models and compute Berry curvature, surface states, and Fermi arc spectra via WannierTools. For SrSi2, a 12% tensile strain opens a small band gap of similar to 0.055 eV along the Gamma-X path, reducing its semimetallic behavior. Applying an electric field of 0.51 V/& Aring; lifts degeneracies at Weyl nodes, while a stronger field of 1.29 V/& Aring; enlarges the gap to similar to 0.058 eV and redistributes Berry curvature near nodal regions, marking a clear quantum phase transition. In CoSi, strong directional sensitivity to strain and field is observed: a 10% tensile strain induces a similar to 0.035 eV gap at the Gamma point, widening to similar to 0.11 eV at 15%, while the R point remains gapless. Under an electric field of 0.51 V/& Aring;, a selective gap of similar to 0.02 eV appears at the R point, expanding to similar to 0.065 eV at 1.29 V/& Aring;. These findings reveal precise and anisotropic control of band topology and Fermi-arc connectivity in CoSi and SrSi2, demonstrating that mechanical and electrical tuning can drive semimetal to insulator transitions in chiral and non-centrosymmetric systems. This work provides a comprehensive framework for designing topological materials with controllable quantum states for electronic and spintronic applications.

Topological insulators, renowned for their exceptional electronic properties, exhibit insulating interiors and conductive surfaces, rendering them highly suitable for quantum computing and advanced electronic devices. Understanding the fundamental characteristics of these materials, including the effects of dimensional transitions, is crucial for comprehending their distinctive electronic properties. This study offers a comprehensive theoretical analysis of the structural, elastic, and optoelectronic properties of topological insulators (TIs). The research encompasses an in-depth examination of the materials in both bulk and slab forms. Employing density functional theory (DFT) with spin-orbit coupling (SOC), and utilizing first-principles calculations, the study elucidates significant findings. It reveals that the structural differences between Bi2Se3 and Bi2Te3 bulk materials significantly affect their physical properties. Elastically, both forms meet the Born-Huang stability criteria, indicating their stability. However, the transition from bulk to slab leads to reduced mechanical stability, a result of diminished interatomic bonding and anisotropic behaviour. The shift from bulk to slab also marks significant changes in electronic behaviour due to strong spin-orbit interactions, affecting the material's response to external stimuli. Optically, variances in dielectric functions, refractive indices, extinction indices, absorption coefficients, and reflectivity between the bulk and slab forms were observed, attributed to surface and interface effects in slab configurations. These changes influence electronic transitions and, consequently, the optical properties. The findings highlight how dimensionality impacts the electronic and optical characteristics of topological insulators, offering valuable insights for future applications and research.

The pursuit of high-efficiency, environmentally friendly photovoltaics has intensified the search for leadfree perovskite solar cells (PSCs). This study comprehensively investigates the potential of inorganic cesium tin chloride (CsSnCl3) as a stable, non-toxic absorber material via a combined computational approach. To address the inherent instability of Sn2+, we propose strategic doping with aluminum (Al) and indium (In). First-principles density functional theory (DFT) calculations reveal that doping successfully widens the band gap from 0.95 eV to 1.63 eV (Al) and 1.95 eV (In), induces beneficial p-type conductivity, enhances optical absorption, and improves structural stability. Subsequently, device-level performance is evaluated through SCAPS-1D simulations of pristine CsSnCl3 in three novel heterojunction architectures: FTO/ZnO/CsSnCl3/Spiro-OMeTAD/Au, FTO/C60/CsSnCl3/CuSCN/Au, and FTO/WS2/CsSnCl3/P3HT/Au. These configurations yield high power conversion efficiencies (PCEs) of 24.89%, 24.53%, and 23.03%, respectively, at an 800 nm absorber thickness. The ZnO/Spiro-OMeTAD structure achieves superior performance due to optimal band alignment and minimized recombination losses. Further optimization of the absorber thickness boosts the PCE to 25.00% for the leading device. All configurations exhibit exceptional quantum efficiency, exceeding 99%. Our findings not only validate doped CsSnCl3 as a highly promising lead-free absorber but also underscore the critical importance of synergistic materials engineering and device architecture optimization in developing efficient and sustainable PSCs.

Chromium-and titanium-doped aluminum phosphides have the potential to exhibit half-metallic ferromagnetism, making them a promising candidates for spintronic applications. However, accurately capturing the electron-electron correlations within the d orbital to predict the magnetic and electronic properties remains a challenge when standard density functional theory (DFT) is used. In this study, we used the PBE functional and its Hubbard U correction (PBE+U) to accurately capture the on-site Coulomb interaction of localized d orbitals. The results reveal that incorporating the Hubbard U correction transforms the indirect bandgap of Al0.75Cr0.25P into the direct bandgap in the spin-down channel and improves the electronic character of Al0.875Cr0.125P from the metallic state to the half-metallic state. Moreover, it enhances the spin magnetic moment of both the dopant atoms and the doped systems and increases the occupancy of the d-orbital components in the spin-up channel. These findings offer strong evidence of the impressive half-metallic behavior of Cr-and Ti-doped AlP when the Hubbard U correction is applied, highlighting their significant potential for future spintronic applications.

Choosing an appropriate H2/O2 recombination catalyst is crucial for enhancing efficiency in hydrogen technologies. This study used density functional theory calculations to investigate PtxPd1-x (0 <= x <= 1) alloys with varying slab thicknesses and surface areas. The performance of these alloys and the reaction intermediates (O, H, OH, OH + H, H2O) formed on the catalyst surfaces for the H2/O2 recombination reaction was analysed. Catalytic activity of pristine Pd (111) and PtPd3, PtPd, Pt3Pd, and Pt7Pd (111) alloy surfaces was evaluated using adsorption and reaction energies. Stability was found along the (111) Miller index for all tested alloys. Strong surface adsorption was observed on PtPd (111) and PtPd3 (111) surfaces, while weaker adsorption occurred on Pt7Pd (111) surfaces. Lower activation energies were observed on Pt7Pd (111) and Pt3Pd (111) surfaces for the rate-determining step (O* + H* -> *OH), compared to pristine Pd (111). In contrast, the *OH formation step was inhibited on PtPd (111) and PtPd3 (111) surfaces due to strong surface absorption of reaction intermediates. Overall, Pt3Pd (111) and Pt7Pd (111) surfaces are promising alternative catalysts for H2/O2 recombination, especially in the rate-determining *OH formation step.

This study reports a new form of nitrogen-doped activated carbon (AC5-600) produced from a blend of sawdust (SD) and fish waste (FW) treated with urea and ZnCl2 for the adsorption of toxic metals and dyes. The adsorbent was also explored in the treatment of acid brown 14 (AB14) and acid orange 7 (AO7) dye molecules and hexavalent chromium (Cr6+) ions. The pH controls the sorption of individual contaminants, with an observed superlative % of individual contaminants removed at pH 1.5. Removal at pH was credited to the electrostatic interaction (EI) between the anion dyes and Cr6+ species at this pH and the protonated sites accessible on the AC5-600 adsorbent surface. Based on the error values obtained from the non-linear modelling (NLM) of the kinetic and isotherm models, the Elovich (ELM-AB14 and Cr6+), pseudo-first- (PFOM-AB14) and second-order models (PSOM-AB14, AO7 and Cr6+) and the Freundlich (FRHM) model were found to ideally define the sorption of the various contaminants. The determined maximum sorption capacity (Qm) based on the NLM was 1114, 1929 and 318 mg.g-1 for AB14 dye, AO7 dye and Cr6+ ions, respectively. Based on the computational adsorption calculations, the sorption energies for the AO7 and AB14 dyes were -4.492 and -8.090 eV and 2.563, 1.789, 1.226 and 1.928 eV for Cr2, CrO3, CrO4, and CrO4H species. AB14 and AO7 dyes and Cr6+ ions adsorption to synthesised AC5-600 was predicted employing the response surface methodology (RSM) and artificial neural network (ANN) models. The ANN model was more effective in predicting AB14 and AO7 dyes and Cr6+ ions adsorption than the RSM, and it was highly applicable in the sorption process.

Significant attention is currently being given to two-dimensional (2D) materials due to their various attractive features, making them useful for gas scrubbing, photovoltaics, electrocatalysts, photocatalysts, electronic applications, and so forth. This review focuses on molybdenum disulfide (MoS 2) , MXenes, and MoS 2 /MXene heterostructures for photovoltaic and water splitting applications. The current state-of-the-art on hydrogen evolution reaction (HER), water splitting and electrolysis, and the application of 2D materials based on MoS 2 and MXene, as well as their heterostructures for water splitting and photovoltaics, are discussed. The review article addresses and highlights knowledge gaps as well as notable limitations toward the creation and application of novel 2D materials and heterostructures based on MoS 2 and MXene as possible candidate materials in photovoltaic and water splitting applications. Thus, MoS 2 and MXene-based heterostructure catalysts can offer a solution because they are affordable, earth-abundant, stable, and present an opportunity for cost reduction.

Antimony (Sb)-doped CsSnCl3 halide perovskites have emerged as promising candidates for lead-free perovskite solar cells due to their enhanced stability and tunable optoelectronic properties. This study employs first-principles Density Functional Theory (DFT) calculations to investigate the structural, electronic, optical properties of pristine and Sb-doped CsSnCl3, and SCAPS-1D simulations to investigate the photovoltaic characteristics of CsSnCl3. Structural optimizations reveal stable lattice configurations, with doping slightly expanding the lattice parameters. Sb doping significantly widens the bandgap from 0.95 eV (pristine) to 1.93 eV (3.7% doping) transitioning the material to an n-type semiconductor. Optical analyses show enhanced absorption and refractive properties in the visible spectrum, vital for efficient light harvesting. SCAPS-1D simulations indicate a PCE of 22.79% for CsSnCl3 based solar cell, with optimal absorber thickness at 1300 nm. The results demonstrate that Sb doping addresses the stability issues of tin-based perovskites while enhancing their photovoltaic performance, paving the way for sustainable, lead-free solar technologies.

We have acquired the overall energy spectrum of the Dirac model with a novel sort of potential in this meticulous investigation utilizing the Greene-Aldrich assumption and the well-known Nikiforov-Uvarov functional analysis method. We present a review of the Dirac equation solutions for the spin symmetric issue and the pseudospin symmetric limited problem using the model of Cosine Hyperbolic Yukawa potential, ensuring a comprehensive understanding. By considering different scenarios and constant values of the vibration and rotation quantum numbers, we have successfully determined the eigenvalues and eigenfunctions of the attractive scalar and repulsive vector for each given spin-orbit coupling quantum number. The objective was to determine binding energies and apply the results to specific diatomic molecules and their spectroscopic parameters. To gain a deeper understanding of the properties of diatomic molecules, it is crucial to study their chemical bond energy spectrum, which enables the assessment of their thermodynamic and magnetic properties, including the free energy and mean energy, etc. Additionally, the magnetization, and magnetic susceptibility. These convincing results strongly corroborate the data in the research and provide additional support for our methodology.

We conduct an in-depth investigation of the structural, electronic, vibrational, thermodynamic, and thermoelectric characteristics of Na-Bi-based compounds, specifically tetragonal NaBi, hexagonal NaBi3, and cubic Na3Bi, using advanced first-principles calculations in conjunction with machine learning (ML) models. We used density functional theory (DFT) with spin-orbit coupling (SOC) to figure out the electronic structure, phonon dispersions, and thermoelectric transport using Boltzmann transport theory. Our findings validate the Dirac semimetal nature of cubic Na3Bi and demonstrate varied topological and thermodynamic properties within the Na-Bi family. To speed up the prediction of the thermoelectric figure of merit (ZT) while enhancing interpretability to understand at the feature level, we trained supervised ML models [Random Forest (RF) and Neural Network (NN)] on thermoelectric results from DFT. It is possible to directly compute the figure of merit (ZT) from DFT-derived transport coefficients such as the Seebeck coefficient, electrical conductivity, and thermal conductivity. However, machine learning (ML) models serve as powerful surrogate predictors, enabling rapid screening of derivative compounds and quantitative assessment of feature importance through SHAP (SHapley Additive exPlanations) analysis. At low temperatures, RF models consistently outperformed NN models, but both performed well at high temperatures. SHAP analysis showed that the Seebeck coefficient has the biggest effect on ZT in all regimes. This integrated, physics-informed, and data-driven methodology demonstrates that machine learning can significantly augment first-principles approaches. It accelerates predictions, guides feature prioritisation, and enhances design capabilities. The developed workflow provides a generalizable and interpretable framework for the predictive modeling of advanced topological thermoelectric materials.

This study explores the impact of antimony (Sb) doping on cesium tin bromide (CsSnBr3), a lead-free perovskite material, for solar cell applications. Density Functional Theory (DFT) is utilized to investigate the structural, electronic, and optical properties of both pristine and Sb-doped CsSnBr3. The DFT analysis reveals that Sb doping enhances material stability, while also improving optical absorption and tuning the electronic bandgap for better visible-light harvesting. In parallel, the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D) is employed to assess the photovoltaic performance of pristine CsSnBr3, yielding a baseline efficiency of up to 19.25%. The SCAPS-1D simulation is limited to the undoped material, establishing a reference point for solar cell performance. Based on the DFT findings, Sb doping is inferred to potentially enhance photovoltaic efficiency beyond this baseline. These results highlight Sb-doped CsSnBr3 as a promising, efficient, and eco-friendly alternative to toxic lead-based perovskites for sustainable solar energy technologies.

The development of highly effective dehydrogenation catalysts presents significant potential for storing hydrogen solutions with favorable economic advantages. In this study, we examined the dehydrogenation of cyclohexane on Pt-skin AgPt3(111) and Ag3Pt(111) surfaces in comparison with that on a Pt(111) pristine surface by applying density functional theory. We assessed the performance of various exchange-correlation functionals (PBE, BEEF-vdW, optPBE-vdW, and PBE-D3) in predicting the adsorption energy of cyclohexane on Pt-AgPt3(111), Pt-Ag3Pt(111), and Pt(111) surfaces and compared them to the experimental data. Through systematic calculations, we analyzed the electronic and structural properties of catalysts, adsorption energies of cyclohexane and intermediate molecules on various Ag-Pt alloy surfaces, surface charge distribution, dehydrogenation processes, and the effect of Ag concentration on its activity. The findings indicate that an increase in the Ag content leads to a closer shift of the d-band center of the Pt atom toward the Fermi level, moving from -2.31 to -1.81 eV. This shift increases surface charge accumulation. This gradual accumulation enhances the adsorption of cyclohexane. Notably, the dehydrogenation of cyclohexane on Pt-skin Ag3Pt exhibited a lower reaction energy, with a value of 1.31 eV compared to the pristine Pt(111) catalyst. This study revealed that the Pt-skin Ag3Pt(111) catalyst exhibits enhanced performance for the dehydrogenation of cyclohexane, which should stimulate additional experimental studies.

This study investigates the behavior of spinless particles under the influence of scalar and vector potentials by analytically solving the Klein-Gordon equation using the Nikiforov-Uvarov functional analysis method, coupled with the Hellmann and modified Kratzer potentials, employing the Greene-Aldrich approximation for the centrifugal term. The analytical energy eigenvalues and eigenfunctions were utilised to examine the energy spectra of specific diatomic molecules (CO, NO, N2, and CH), demonstrating the correlation of these properties with potential parameters and quantum numbers. In addition to the analytical results, machine learning techniques like Random Forest and Neural Network regressors were used to model and predict the energy spectra based on the calculated data. This made it possible to swiftly explore energy landscapes. The ML models showed great agreement with the analytical results and were better at extrapolating to new quantum numbers and molecular types. This hybrid analytical-ML approach is a strong way to speed up the study of diatomic molecular systems. It combines the rigour of quantum mechanics with data-driven predictions and makes it possible to efficiently screen molecular energy spectra in theoretical and computational chemistry.

This study aims to predict the biogas produced from ozone (O3) pre-treated green algae Ulva Lactuca (UL) combined with three different inoculums at varying times using RSM, ANN, ANFIS, and ARIMA models. The results revealed that the O3 pretreatment significantly enhanced biogas production, by achieving biogas yield (BioY) values of 498, 211, and 156 mL/g.VS under optimal conditions. Similarly, it was discovered that the ANFIS outperformed RSM and ANN, with R2 values of 1.0000, 0.9718, and 0.9821, and RMSEs of 0.005, 5.30, and 12.91, respectively. The validated optimization results predicted BioY values of 498.0, 156.0, and 315.0 mL/ g.VS (ANFIS), and 499.5, 156.6, and 315.1 mL/g.VS (RSM). Using a hybrid RSM-GA approach, the highest BioY values of 500.0 mL/g.VS at O3 = 21.35 mg/min and 60.00 min (cow manure), 319.57 mL/g.VS at O3 = 30.00 mg/min and 60.00 min (sludge), and 154.55 mL/g.VS at O3 = 19.82 mg/min and 56.99 min (sediment) were achievable. Additionally, the time-series analysis revealed comparable performance between ARIMA and ANN in modelling cumulative BioY, with high R2 and low MSE/RMSE. A net energy gain of 2.731 kWh/kg VS and 930 % efficiency was achieved, with a payback period of 1.02 years, which confirmed the process's techno-economic feasibility. These findings underscore the potential of O3 pretreatment, proper utilization of wastes, and machine learning modelling in optimizing sustainable biogas production.

Cesium tin halide perovskites (CsSnI3) are promising lead-free materials for photovoltaic applications due their high absorption coefficients and tunable bandgaps. However, stability challenges limit their practical use. This study investigates the impact of 3.7% antimony (Sb) doping on the structural, electronic, optical, and photovoltaic properties of CsSnI3 using Density Functional Theory (DFT) calculations and SCAPS-1D simulations. DFT results reveal that Sb doping induces a slight lattice expansion in a 3 x 3 x 3 supercell and widens the bandgap from 0.46 eV to 1.72 eV, transitioning CsSnI3 to n-type semiconductor behavior, which enhances stability by potentially reducing Sn2+ oxidation. However, optical analyses show a weakened response, with reduced dielectric function, refractive index, and absorption coefficient, indicating trade-off between stability and light absorption. SCAPS-1D simulations of pristine CsSnI3-based solar cells (ITO/PCBM/CsSnI3/Cu2BaSnS4/Au) yield a power conversion efficiency (PCE) of 29.24%, with a shortcircuit current density of 29.37 mA/cm2, open-circuit voltage of 1.29 V, and fill factor of 77.13%, improving to 30.55% at 1600 nm absorber thickness. These findings highlight CsSnI3's potential as a lead-free absorber and guide optimization of Sb doping for balanced stability and photovoltaic performance.