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Thickness-modulated thermochromism of vanadium dioxide thin films grown by magnetron sputtering
摘要： Vanadium dioxide (VO2) films were prepared on soda-lime glass by direct current magnetron sputtering at 320 °C. Effects of film thickness on the microstructure, surface morphology and thermochromic performance of VO2 films were investigated. X-ray diffraction showed that the deposited films have strong preferred orientation of VO2 (011) lattice when the film thickness higher than 102 nm. The calculated grain sizes of VO2 films increased from 16.05 nm to 34.56 nm continuously with the increasing of film thickness. UV/VIS/NIR spectrophotometer showed that the visible transmittance deceased while the infrared transmittance switching efficiency increased as the film thickness increased from 79 nm to 264 nm. Additionally, the optical band gaps of VO2 films were in a range of 1.15 eV–1.40 eV, and the thicker film exhibited the smaller value. Moreover, the results of measured temperature-dependent electrical resistivity of these VO2 films showed that the phase-transition temperature is in a range of 53–60 °C, which is much lower than that of single-crystal VO2 (68 °C). With the film thickness increasing, the metal–semiconductor phase transition becomes more obvious. Overall, films with thickness in the range of 80–100 nm showed comparatively relatively balanced combination of visible transmittance and solar switching efficiency.
关键词： Thermochromic performance,Film thickness,Vanadium dioxide,Magnetron sputtering
更新于2025-09-23 15:23:52
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Thickness dependence of structural, morphological and optical properties of Mn-Co-Ni-O thin films grown by chemical solution deposition on SiO2/Si(100) substrate
摘要： Mn1.56Co0.96Ni0.48O4 (MCNO) thin film with different thicknesses ranging from 180 nm to 600 nm were deposited onto a SiO2/Si(100) substrate at 600 °C by using the chemical solution deposition method. The thickness dependent structural and optical properties of the MCNO films were investigated in this study. As identified by the SEM pictures and X-ray diffraction (XRD) spectra, all samples showed polycrystalline cubic spinel structure, and the stoichiometric status is improved with growing thickness according to XRD results. Spectroscopic ellipsometry spectra were measured in this study to investigate the thickness dependent optical properties of MCNO film in the range of 300-1000 nm. The samples showed three absorption structures locating at 1.6-1.9 eV, 2.6 eV, and above 3.5 eV, corresponding to the charge transfer transition involving 2p orbitals of O2- and 3d orbitals of Mn and Co ions, respectively. The absorption structure at above 3.5 eV decreases gradually as the thickness grows, while the peak around 1.6-1.9 eV weakens slightly before it enhances again with film thickness above 430 nm, which can be explained by a combined effect of crystallinity improvement and increase in Mn4+/Mn3+ ratio.
关键词： optical properties,Mn1.56Co0.96Ni0.48O4 thin film,thickness dependence,chemical solution deposition,absorption structures
更新于2025-09-23 15:22:29
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Effect of film thickness and evaporation rate on co-evaporated SnSe thin films for photovoltaic applications
摘要： SnSe thin films were deposited by a co-evaporation method with different film thicknesses and evaporation rates. A device with a structure of soda-lime glass/Mo/SnSe/CdS/i-ZnO/ITO/Ni/Al was fabricated. Device efficiency was improved from 0.18% to 1.02% by a film thickness of 1.3 mm and evaporation rate of 2.5 ? s?1 via augmentation of short-circuit current density and open-circuit voltage. Properties (electrical, optical, structural) and scanning electron microscopy measurements were compared for samples. A SnSe thin-film solar cell prepared with a film thickness of 1.3 mm and evaporation rate of 2.5 ? s?1 had the highest electron mobility, better crystalline properties, and larger grain size compared with the other solar cells prepared. These data can be used to guide growth of high-quality SnSe thin films, and contribute to development of efficient SnSe thin-film solar cells using an evaporation-based method.
关键词： SnSe thin films,film thickness,co-evaporation,photovoltaic applications,evaporation rate
更新于2025-09-23 15:21:01
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Influence of Film Thickness on the Electronic Band Structure and Optical Properties of Pa??Ia??N CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3a??x</sub> Cl <sub/>x</sub> Perovskite Solar Cells
摘要： The phenomenal optoelectronic properties of lead halide perovskites have spurred a remarkable worldwide effort to develop them as photovoltaic materials. The morphology and crystal structure of the films have a profound effect on the characteristics and performance of devices; however, the influence of underlying hole transport layers (HTLs) or electron transport layers (ETLs) and film thickness on the film morphology and electronic characteristics remains unclear. In this work, we have studied the characteristics of perovskite films with variable thickness, including the morphological, crystal, optical properties and electronic band structure of these films using scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet-visible (UV-vis) absorption spectra. The corresponding performance of perovskite solar cells (PSCs) devices was correlated with the different thicknesses of perovskite films. Additionally, ultraviolet photoelectron spectroscopy (UPS) results show that for the optimized perovskite thickness (310 nm) the interfacial dipole (?) formed at the interface with the substrate reaches its highest value of 0.23 eV. Hence, this strong dipole compared to other thicknesses allows the carriers to be swept out efficiently.
关键词： Film thickness,Perovskite,Solar cell,Interfacial dipole
更新于2025-09-23 15:19:57
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Sub-400 nm film thickness determination from transmission spectra in organic distributed feedback lasers fabrication
摘要： The design and fabrication of thin-film based organic optoelectronic devices require knowledge of the film optical properties. A low-cost and non-destructive method often used for optical characterization of films is the well-established spectrophotometric envelope method. However, this method is typically limited to thickness above 400 nm, a value often higher than that of the films involved in these devices. This paper studies a procedure to obtain the thickness of sub-400 nm active films from their spectrophotometric trace when the refractive index is previously known. The proposed procedure is based on comparing the experimental transmission spectrum in the transparent spectral window with that obtained by simulation. The capabilities of the proposed method are demonstrated here by its application in the fabrication of organic distributed-feedback lasers where a fine control of film thickness is important to obtain an optimized and reproducible response. Results were verified with other techniques, such as ellipsometry and profilometry. Thus, with the proposed method, film thickness can be easily determined down to 40 nm maintaining an accuracy of about 5 nm even for films with low refractive index (1.5-1.7). Different methods to determine refractive index of these films are also discussed.
关键词： Optical characterization,Thin film thickness,Transmission spectra,Distributed feedback lasers
更新于2025-09-19 17:13:59
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Effects of the film thickness and poling electric field on photovoltaic performances of (Pb,La)(Zr,Ti)O3 ferroelectric thin film-based devices
摘要： The ferroelectric photovoltaic (FPV) effect obtained in inorganic perovskite ferroelectric materials has received much attention because of its large potential in preparing FPV devices with superior stability, high open-circuit voltage (Voc) and large short-circuit current density (Jsc). In order to obtain suitable thickness for the ferroelectric thin film as light absorption layer, in which, the sunlight can be fully absorbed and the photo-generated electrons and holes are recombined as few as possible, we prepare Pb0.93La0.07(Zr0.6Ti0.4)0.9825O3 (PLZT) ferroelectric thin films with different layer numbers by the sol-gel method and based on these thin films, obtain FPV devices with FTO/PLZT/Au structure. By measuring photovoltaic properties, it is found that the device with 4 layer-PLZT thin film (~300 nm thickness) exhibits the largest Voc and Jsc and the photovoltaic effect obviously depends on the value and direction of the poling electric field. When the device is applied a negative poling electric field, both the Voc and Jsc are significantly higher than those of the device applied the positive poling electric field, due to the depolarization field resulting from the remnant polarization in the same direction with the built-in electric field induced by the Schottky barrier, and the higher the negative poling electric field, the larger the Voc and Jsc. At a -333 kV/cm poling electric field, the FPV device exhibits the most superior photovoltaic properties with a Voc of as high as 0.73 V and Jsc of as large as 2.11 μA/cm2. This work opens a new way for developing ferroelectric photovoltaic devices with good properties.
关键词： Film thickness,Ferroelectric thin film,Ferroelectric photovoltaic devices,Depolarized electric field,Inorganic perovskite
更新于2025-09-16 10:30:52
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Combined parametric optimization of P3HT: PC70BM films for efficient bulk-heterojunction solar cells
摘要： In this report, the effects of photoactive blend compositions, film thicknesses, and annealing conditions on the P3HT:PC70BM solar cells performance and reproducibility was investigated. The performance of prepared devices was described by examining their absorption spectra, current-voltage characteristics and external quantum efficiency (EQE). The thickness of active layer was achieved as 190 nm, 125 nm, and 90 nm, by maintaining the spin speed. Current density (Jsc) slightly increases from 6.39 to 7.15 mA/cm2 with increase in thickness from 90 to 125 nm; however, with further increase in film thickness (190 nm), the Jsc was reduced to 4.39 mA/cm2. To optimize the device performance, four different compositions of PC70BM (1:0.6, 1:0.8, 1:1, and 1:12) were investigated at the most favorable film thickness ~ 125 nm. The effect of different PC70BM compositions on photovoltaic performance was demonstrated by X-ray diffraction (XRD) and Raman measurements that illuminated modification in structural properties. Additionally, annealing condition led to achieve the good phase separation for efficient charge separation and transport within P3HT: PCBM film which further leads to increased efficiency (PCE ~ 3.31%). These effects deliver valued facts for the choices of PC70BM amount in P3HT:PC70BM system, and this efficient device optimization might be useful in other efficient photovoltaic systems for better performance through excellent reproducibility.
关键词： P3HT:PC70BM,Composition,Film thickness,Solar cells,Photoactive layer
更新于2025-09-12 10:27:22
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Thickness-Dependent Swelling Behavior of Vapor-Deposited Smart Polymer Thin Films
摘要： In this contribution, the temperature-dependent swelling behavior of vapor-deposited smart polymer thin films is shown to depend on cross-linking and deposited film thickness. Smart polymers find application in sensor and actuator setups and are mostly fabricated on delicate substrates with complex nanostructures that need to be conformally coated. As initiated chemical vapor deposition (iCVD) meets these specific requirements, the present work concentrates on temperature-dependent swelling behavior of iCVD poly(N-isopropylacrylamide) thin films. The transition between swollen and shrunken state and the corresponding lower critical solution temperature (LCST) was investigated by spectroscopic ellipsometry in water. The films’ density in the dry state evaluated from X-ray reflectivity could be successfully correlated to the position of the LCST in water and was found to vary between 1.1 and 1.3 g/cm3 in the thickness range 30?330 nm. This work emphasizes the importance of insights in both the deposition process and mechanisms during swelling of smart polymeric structures.
关键词： X-ray reflectivity,spectroscopic ellipsometry,vapor-deposited,smart polymers,iCVD,LCST,film thickness,swelling behavior,cross-linking
更新于2025-09-11 14:15:04