Optimization of optical and electrical properties of active semiconducting layers is required to enhance thin film solar cells' efficiency and consequently became the cornerstone for sustainable energy production. Computational studies are one of the ways forward to optimize solar cells’ characteristics. In this study, Silvaco-Atlas, a powerful software that excels in both 2D and 3D electrical simulations of semiconductors has been used for the simulation in order to investigate the solar cell properties. The architecture of the solar cell simulated was FTO/ZnO/In₂S₃/CuInS₂/Mo. This study aims to optimize solar cell efficiency by optimizing film thicknesses and carrier concentrations via simulation. The designed solar cell was exposed to the presence of a sun spectrum of AM1.5 from a 1kW/m² incident power density at 300K. The thickness values of the window (ZnO), absorber (CuInS₂) and buffer (In₂S₃) layers were varied to record a solar cell's optimum thickness. The resulting FTO/ZnO/In₂S₃/CuInS₂/Mo solar cell formed by simulation is presented. The best efficiency and fill factor of the solar cell simulated were found to be 41.67% and 89.19%, respectively. The recorded values of current density and the open circuit voltage of the cell were 40.33mA/cm² and 1.15 V, respectively. Additionally, the maximum power of the simulated solar cell device was 41.68 mW. Optimization results revealed that the most efficient cell found was made up of a window layer with a thickness of 0.03μm, an absorber layer with a thickness of 6.0μm and a buffer layer with a thickness of 0.2μm. The optimized carrier concentration of ZnO, In₂S₃ and CuInS₂ was respectively 1e21 cm^-3, 1e20 cm^-3, 3e18 cm^-3 and the optimized Al-doped ZnO value was 1e25 cm^-3. The Absorption spectra indicated that the solar cell's peak absorption occurs between 350 nm and 1250 nm and presented a good external quantum efficiency (EQE) of around 84.52% to 92.83% which indicates good efficiency in the visible domain. This performance is attributed to the transparency of FTO, ZnO and good absorption of In₂S₃ and CuInS₂ thin films.

The design of a high energy performance building requires an assessment of the various design options. Energy simulation offers interesting possibilities for clarifying the architect’s decisions at this level, especially in the initial design phases where the greatest opportunities for optimization lie. The aim of this work is to develop an approach for the evaluation and optimal use of energy simulation in the building design phases. To do this, EnergyPlus building simulation software was used to simulate the energy consumption of the Faculty of Electrical Engineering building at “Gheorghe Asachi” Technical University in Iasi, in order to identify the factors influencing energy consumption in buildings. The results of this study show that an increase in the cooling setpoint temperature from 22 °C to 28 °C in the roof construction can reduce operating temperatures by 14.2% and 20.0%, respectively. This optimization could significantly reduce the hours of thermal discomfort, in a ratio of 6.0 and 3.25, respectively. Consequently, optimizing parameters linked to design and the heating and cooling systems within the building makes it possible to achieve energy savings and ensure thermal comfort in buildings.

This study presents the influence of pH control agents and pH value on the physical properties of ZnO thin films obtained by chemical bath deposition. ZnO thin films were synthesized on glass substrates using precursor solutions of different pHs prepared from two bases: sodium hydroxide (NaOH) and ammonia (NH₃). The effect of pH values on the morphological, structural, and optical properties of ZnO thin films was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV–Visible spectroscopy. XRD results showed that all the synthesized ZnO thin films are polycrystalline and crystallize in a hexagonal wurtzite structure. The crystallite size, calculated using the Debye–Scherrer formula, varied from 10.50 nm to 11.69 nm for ZnO thin films obtained with NH₃ and from 20.79 nm to 27.76 nm for those obtained with NaOH. FTIR analysis confirmed the presence of functional groups. SEM images indicated that not only the base but also the pH affects the morphology of the films, giving rise to different granular shapes. Overall, the ZnO thin films obtained with NaOH looked more mesoporous compared to those obtained with NH₃. Optical characterization results showed that whatever the base used, the pH of the precursor solution affected the ZnO thin film transmittance. Films synthesized with NH₃ exhibited the best transmittance (80%) at pH 8.5, while the best transmittance (81%) of films synthesized with NaOH was obtained at pH 8 in the visible region. Based on optical and morphological properties, ZnO films obtained from NH₃ at pH 8.5 are found to be more suitable as photoanodes in dye-sensitized solar cells.

This study investigates the effect of deposition time on the structural, morphological, and optical properties of ZnO thin films synthesized by single-step chemical bath deposition (CBD) without the use of a seed layer. The films were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Visible spectroscopy in order to establish correlations between growth conditions and film properties. XRD analysis confirmed that all synthesized films are polycrystalline and crystallize in the hexagonal wurtzite structure, with average lattice parameters of a = 3.247 Å and c = 5.209 Å. The crystallite size increased slightly from 13.27 nm to 14.05 nm with increasing deposition time, indicating improved structural ordering and crystallinity. FTIR spectra verified the presence of characteristic Zn–O vibrational modes together with surface hydroxyl groups and other functional bonds related to the growth process. SEM images revealed a strong dependence of surface morphology on deposition time: ZnO microrods evolved from loosely distributed to more compact and densely packed assemblies as the deposition progressed, confirming enhanced film coverage. Optical measurements highlighted significant modifications in the transparency and band structure of the films. The average optical transmittance in the visible range decreased progressively from 68% to 52% when deposition time was extended from 30 to 120 minutes, reflecting increased film density. Concurrently, the optical band gap narrowed from 3.27 eV to 3.22 eV. These findings demonstrate that single-step CBD provides a reliable and controllable route for synthesizing ZnO thin films with tunable physical properties.

The present study examines the role of the hexamethylenetetramine (HMTA)-to-zinc nitrate hexahydrate (ZNH) molar ratio in controlling the physical properties of zinc oxide (ZnO) thin films obtained by chemical bath deposition (CBD) for potential applications in dye-sensitized solar cells (DSSCs). ZnO thin films were synthesized on glass substrates using aqueous solutions with different HMTA-to-ZNH molar ratios of 0, 1, 2, 3, 4, 5, and 6. The results show that this parameter strongly influences the crystallinity, morphology, and optical characteristics of the films. The X-ray diffraction analysis shows that all the ZnO thin films synthesized are polycrystalline and crystallize in a hexagonal wurtzite structure, with a fluctuating variation in crystallite size (9.5 to 43.7 nm), indicating crystal growth modulated by HMTA. The presence of characteristic functional groups and chemical bonds in ZnO thin films was confirmed by Fourier transform infrared spectroscopy. Scanning electron microscope images revealed that the molar ratio of HMTA/ZNH in the bath solution affected the morphology of the films through grain shape. The films became more compact as molar ratio increased, showing the presence of agglomerated nanotubes. UV-visible analysis showed that films obtained with HMTA/ZNH molar ratio of 4 exhibited the highest transmittance (85%) while those elaborated without HMTA exhibited the lowest transmittance (60%) indicating the impact of HMTA on physical properties of ZnO thin films. Based on structural, morphological, and optical properties, ZnO thin films obtained with HMTA/ZNH molar ratio of 4 are more suitable to be used as a compact electron transport layer in DSSCs to limit charges recombination.

The collection and transport of charges at the electrodes are the main factors limiting the efficiency of organic solar cells. Zinc oxide (ZnO) in nanostructured form helps to overcome this problem by introducing a ZnO buffer layer between the photoanode and the donor material. To achieve this, the ZnO thin film must exhibit good crystallinity, along with good electrical conductivity and high optical transparency in the visible range. The aim of this work is to investigate the effect of precursor sources and precursor concentrations on the structural, morphological, and optical properties of ZnO thin films. Three different precursor sources have been used: zinc acetate, zinc chloride and zinc nitrate. In each deposition solution, the precursor concentration varied from 0.1 M to 0.3 M. The ZnO films were deposited on glass substrates and all the films were annealed at 400°C for 3 hours. The structural, morphological and optical properties of deposited films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy respectively. XRD results showed that, regardless of the precursor source, all the ZnO films are polycrystalline with a hexagonal wurtzite structure. ZnO films obtained from acetate and nitrate sources crystallize preferentially along (002) and the peak intensity increases as the precursor concentration increases. SEM images showed that all the ZnO films are homogeneous, but films deposited from zinc acetate and zinc nitrate looked more compact and smoother than those obtained with zinc chloride which looked porous. UV-visible spectroscopy results revealed that the films transmittance depends both on precursor source and concentration. ZnO thin films deposited from zinc acetate at 0.3M concentration exhibit the best transmittance of 95% due to their smooth and uniform surfaces. The band gap of ZnO obtained from the zinc acetate precursor decreases with increasing solution concentration. It is found to be 3.29 eV, 3.26 eV, and 3.22 eV for concentrations of 0.1 M, 0.2 M, and 0.3 M, respectively. It therefore appears that ZnO films obtained from zinc acetate can be used as an electron transport layer for solar cells as they exhibit the best crystallinity and the highest transmittance.