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Investigation of Well-Defined Pinholes in TiO2 Electron Selective Layers Used in Planar Heterojunction Perovskite Solar Cells
摘要： The recently introduced perovskite solar cell (PSC) technology is a promising candidate for providing low-cost energy for future demands. However, one major concern with the technology can be traced back to morphological defects in the electron selective layer (ESL), which deteriorates the solar cell performance. Pinholes in the ESL may lead to an increased surface recombination rate for holes, if the perovskite absorber layer is in contact with the fluorine-doped tin oxide (FTO) substrate via the pinholes. In this work, we used sol-gel-derived mesoporous TiO2 thin films prepared by block co-polymer templating in combination with dip coating as a model system for investigating the effect of ESL pinholes on the photovoltaic performance of planar heterojunction PSCs. We studied TiO2 films with different porosities and film thicknesses, and observed that the induced pinholes only had a minor impact on the device performance. This suggests that having narrow pinholes with a diameter of about 10 nm in the ESL is in fact not detrimental for the device performance and can even, to some extent improve their performance. A probable reason for this is that the narrow pores in the ordered structure do not allow the perovskite crystals to form interconnected pathways to the underlying FTO substrate. However, for ultrathin (~20 nm) porous layers, an incomplete ESL surface coverage of the FTO layer will further deteriorate the device performance.
关键词： electron selective layer,pinhole,perovskite solar cell,dip coating,evaporation-induced self-assembly,mesoporous TiO2
更新于2025-09-16 10:30:52
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Elaboration of microporous CeO2 thin layers having nanocrystallites network controlled by Pluronic P123: Impact of key experimental parameters
摘要： Microporous ceria thin ?lms having nanocrystallites network were synthesized by evaporation-induced self-assembly process, using P123 amphiphilic copolymer as structure-directing agent. The impact of key experimental parameters, i.e., the sol ageing, the relative humidity (RH), the thermal treatment, on the thin layer elaboration were investigated. The results show that the organization of the nanoparticles is possible for a sol ageing time lower than 16 days and that the size of the mesophase within the thin layer increases with the relative humidity ?xed during the ?lm deposition. Finally, an increase of the thermal treatment temperature from 300 to 1000 °C leads to the formation of ?uorite-like dioxide material coupled with a loss of nanocrystallites organization and porosity due to the increase of the size of the crystallites. This loss of nanocrystallites organization is more drastic in the direction perpendicular to the surface and less pronounced along the surface. Thus, a compromise between the crystallization and the preservation of the porosity needs to be found.
关键词： relative humidity,P123 amphiphilic copolymer,evaporation-induced self-assembly,nanocrystallites network,thin films,thermal treatment,Microporous ceria,sol ageing
更新于2025-09-16 10:30:52
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Effects of Mg content on keyhole behaviour during deep penetration laser welding of Al-Mg alloys
摘要： This paper concerns the effects of Mg content on keyhole behaviours during the laser welding process of 5754, 5083 and 5A06 Al-Mg alloys. The features of the vapour plume and keyhole area are extracted from high-speed images with image processing methods. The increase of Mg content leads to the increase of hydrodynamic pressure caused by metal evaporation and decrease of surface tension acting on the keyhole wall. The strong metal evaporation and decrease of surface tension help the formation of keyhole, which both result in a large size of keyhole with deep penetration and low frequency of keyhole collapse. However, the impact of metal vapour could be enhanced by the increase of evaporation and the decrease of both surface tension and viscosity, which leads to the frequent generation of swelling at the rear weldpool and poor formation of the weld bead.
关键词： Laser welding,Al-Mg alloy,Plume,Evaporation,Keyhole
更新于2025-09-16 10:30:52
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Effect of Defective Microstructure and Film Thickness on the Reflective Structural Color of Self-Assembled Colloidal Crystals
摘要： Structural color arises from geometric diffraction; it has potential applications in optical materials because it is more resistant to environmental degradation than coloration mechanisms that are of chemical origin. Structural color can be produced from self-assembled films of colloidal size particles. While the relationship between the crystal structure and structural color reflection peak wavelength is well studied, the connection between assembly quality and the degree of reflective structural color is less understood. Here, we study this connection by investigating the structural color reflection peak intensity and width as a function of defect density and film thickness using a combined experimental and computational approach. Polystyrene microspheres are self-assembled into defective colloidal crystals via solvent evaporation. Colloidal crystal growth via sedimentation is simulated with molecular dynamics, and the reflection spectra of simulated structures are calculated using the finite-difference time-domain algorithm. We examined the impact of commonly observed defect types (vacancies, stacking fault tetrahedra, planar faults, and microcracks) on structural color peak intensity. We find that the reduction in peak intensity scales with increased defect density volume. The reduction is less sensitive to the type of defect than to its volume. In addition, the reflectance of structural color increases as a function of the crystal thickness, until a plateau is reached at thicknesses greater than about 9.0 μm. The maximum reflection is 78.8% ± 0.9%; this value is significantly less than the 100% reflectivity predicted for a fully crystalline, defect-free material. Furthermore, we find that colloidal crystal films with small quantities of defects may be approximated as multilayer reflective materials. These findings can guide the design of optical materials of variable structural color intensity.
关键词： crystal film,colloidal self-assembly,evaporation,defect,structural color
更新于2025-09-16 10:30:52
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Controlled Growth of Silver Nanoparticles on Indium Tin Oxide Substrates by Plasma-Assisted Hot-Filament Evaporation: Physical Properties, Composition, and Electronic Structure
摘要： High-density silver (Ag) nanoparticles of controllable size and uniformity were used to enhance conductivity and luminance efficiency in an organic light emitting diode device. As part of this experiment, Ag nanoparticles were deposited on indium tin oxide (ITO) substrates by using plasma-assisted hot-filament evaporation. These nanoparticles mainly exhibited spherical grain morphology, with average diameters ranging between 7.5 and 45.7 nm depending on substrate temperature; the size of Ag nanoparticles are known to increase with rises in substrate temperatures up to 250°C, a phenomenon attributable to thermally induced surface diffusion. With regards to the optical spectra, the characteristics of the localised surface plasmon resonance were directly affected by changes in the physical properties of the Ag nanoparticles, such as diameter and interparticle distance. The X-ray photoemission spectroscopy results revealed the formation of a shell layer of silver oxide on the Ag nanoparticles. This resulted in a significant effect on the optical and electrical properties of the Ag nanoparticles/ITO. The highest density of Ag nanoparticles deposited at 80°C were associated with the lowest sheet resistance and work function at 7.45 Ohm/square and 3.97 eV, respectively, while increases in the oxide formation significantly increased the sheet resistance and work function up to 200°C. The effects of substrate temperature on the morphology, structure, as well as optical and electrical properties of the deposited Ag nanoparticles on ITO are discussed in further detail in this report.
关键词： Substrate temperature,Silver,Surface plasmon resonance,Work function,Silver oxide,Nanoparticles,Plasma-assisted hot-filament evaporation
更新于2025-09-12 10:27:22
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Crystallization Control of Ternary‐Cation Perovskite Absorber in Triple‐Mesoscopic Layer for Efficient Solar Cells
摘要： Controlling the crystallization of organic–inorganic hybrid perovskite is of vital importance to achieve high performing perovskite solar cells. The growth mechanism of perovskites has been intensively studied in devices with planar structures and traditional structures. However, for the printable mesoscopic perovskite solar cells, it is difficult to study the crystallization mechanism of perovskite owing to the complicated mesoporous structure. Here, a solvent evaporation controlled crystallization method to achieve ideal crystallization in the mesoscopic structure is provided. Combining results of scanning electron microscope and X-ray diffraction, it is found that adjusting the evaporation rate of solvent can control the crystallization rate of perovskite and a model for the crystallization process during annealing in mesoporous structures is proposed. Finally, a homogeneous pore filling in the mesoscopic structure without any additives is successfully achieved and a stabilized power conversion efficiency of 16.26% using ternary-cation perovskite absorber is realized. The findings will provide better understanding of perovskite crystallization in printable mesoscopic perovskite solar cells and pave the way for the commercialization of perovskite solar cells.
关键词： mesoscopic,perovskite solar cells,crystallization,solvent evaporation
更新于2025-09-12 10:27:22
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Facile growth of SnS and SnS0.40Se0.60 thin films as an absorber layer in the solar cell structure
摘要： SnS (S1) and SnS0.4Se0.6 (S2) thin films were prepared using thermal evaporation on annealing at 523 K of the thermally deposited films. Compositional analysis of the films reveals the formation of SnS and SnS0.40Se0.60 phase. X-ray diffraction results demonstrate the formation of orthorhombic structure corresponding to SnS and SnS0.40Se0.60 phase. Moreover, a decrease in the intensity of SnS0.40Se0.60 peaks as compared to those of SnS was observed. Thus, causes insertion of selenium (Se) atoms in SnS lattice and results in the modification of lattice parameters. These structural modifications leads to variations in crystallite size, lattice strain and dislocation density, thus, confirms the formation of ternary SnS0.40Se0.60 phase. The changes corresponding to optical parameters are also observed in the films in the form of lower transmission, bandgap value and absorption coefficient on Se insertion. Moreover, both the films exhibit absorption coefficient >105 cm?1 with bandgap values of 1.44 and 1.23 eV and found suitable for absorption in solar cell.
关键词： Tin,Thermal evaporation,X-ray diffraction,Solar absorbers,Bandgap,SnS1?xSex
更新于2025-09-12 10:27:22
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Enhanced efficiency of CdTe Photovoltaic by thermal evaporation Vacuum
摘要： CdTe Cadmium telluride is a hopeful material for large scale photovoltaic applications . This paper we study effect annealing temperature( 200 , 400) for CdTe heterojunction solar cells with thermal evaporation technique in vacuum with rate deposition (4.32 A°/sec) and thickness ( ≈ 400 ±10 nm), solar cells were realization with conversion ef?ciencies of ( 6.4% - 10.8%) . The main focus in this work was to study the annealing temperature dependent conduct of the expansion parameter and the band gap energy of (CdTe ) thin ?lm in solar cells. Room temperature band gap for ( CdTe) is found ( Eg =1.5 to 2) eV for ef?ciency solar cells.
关键词： solar cell,CdTe,Thermal evaporation
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Kerala, India (12–14 June 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Study of plasmonic effect in Cu2ZnSnS4-Ag nanocomposite thin film fabricated by vacuum thermal co-evaporation
摘要： CZTS-Ag nanocomposite thin films were fabricated by co-evaporating CZTS in the form of pellet and Ag powder as source materials simultaneously using vacuum thermal co-evaporator. The weight percentage of Ag to CZTS is increased from 2 to 4%. The as-prepared nanocomposite films were post annealed at 500 °C for 1 hour in a vacuum tubular furnace. The crystal structure of the as-prepared and annealed samples is analyzed by x-ray diffraction. Chemical structure of the prepared films is studied using confocal Raman spectroscopy with an excitation wavelength of 785 nm which depicts the mixed phase formation of SnS and CZTS. The observed blue shift in absorption edge in CZTS as well as broadened absorption in the entire visible region in Ag based CZTS nanocomposite could be due to the effect from Ag nanoparticles, verifying the strong existence of surface plasmon resonance in the visible region.
关键词： surface plasmon resonance,Raman spectroscopy,optical absorption,vacuum thermal co-evaporation,CZTS-Ag nanocomposite
更新于2025-09-12 10:27:22
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Fabrication of efficient CsPbBr3 perovskite solar cells by single-source thermal evaporation
摘要： It is promising to improve the stability of organic–inorganic hybrid halide perovskite solar cells by using all-inorganic perovskite materials. Herein, a facile one-crucible single-source vacuum thermal evaporation (VTE) approach is developed, which is used to evaporate two different melting points materials CsBr (630 °C) and PbBr2 (370.6 °C) to deposit high-quality inorganic CsPbBr3 perovskite films. Molar ratio of PbBr2 to CsBr in their mixture in the crucible is a key factor influencing the stoichiometry, structure, photoelectrical and photovoltaic properties of the CsPbBr3 films. The other important factor is the thickness of the CsPbBr3 films. High-quality CsPbBr3 films with good uniformity and compact and large grains are prepared. Planar CsPbBr3 perovskite solar cells are fabricated giving a high power conversion efficiency of 8.65%. The fabricated CsPbBr3 solar cells exhibit a good stability in air without encapsulation. This study opens up the possibility to deposit multi-element compound thin films by facile single-source VTE of different melting points materials.
关键词： Solar cells,Single-source evaporation,Thickness,Molar ratio,CsPbBr3 films
更新于2025-09-12 10:27:22