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Sol-Gel Processed TiO2 Nanotube Photoelectrodes for Dye-Sensitized Solar Cells with Enhanced Photovoltaic Performance
摘要： The performance of dye-sensitized solar cells (DSCs) critically depends on the efficiency of electron transport within the TiO2-dye-electrolyte interface. To improve the efficiency of the electron transfer the conventional structure of the working electrode (WE) based on TiO2 nanoparticles (NPs) was replaced with TiO2 nanotubes (NTs). Sol-gel method was used to prepare undoped and Nb-doped TiO2 NPs and TiO2 NTs. The crystallinity and morphology of the WEs were characterized using XRD, SEM and TEM techniques. XPS and PL measurements revealed a higher concentration of oxygen-related defects at the surface of NPs-based electrodes compared to that based on NTs. Replacement of the conventional NPs-based TiO2 WE with alternative led to a 15% increase in power conversion efficiency (PCE) of the DSCs. The effect is attributed to the more efficient transfer of charge carriers in the NTs-based electrodes due to lower defect concentration. The suggestion was confirmed experimentally by electrical impedance spectroscopy measurements when we observed the higher recombination resistance at the TiO2 NTs-electrolyte interface compared to that at the TiO2 NPs-electrolyte interface. Moreover, Nb-doping of the TiO2 structures yields an additional 14% PCE increase. The application of Nb-doped TiO2 NTs as photo-electrode enables the fabrication of a DSC with an efficiency of 8.1%, which is 35% higher than that of a cell using a TiO2 NPs. Finally, NTs-based DSCs have demonstrated a 65% increase in the PCE value, when light intensity was decreased from 1000 to 10 W/m2 making such kind device be promising alternative indoor PV applications when the intensity of incident light is low.
关键词： nanotubes,X-ray photoelectron spectroscopy,dye-sensitized solar cells,semiconductor-liquid interface,charge traps
更新于2025-09-19 17:13:59
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SPR responsive xylenol orange functionalized gold nanoparticles- optical sensor for estimation of Al3+ in water
摘要： Xylenol orange functionalized gold nanoparticles (XO-AuNPs), prepared by reducing HAuCl4 in presence of xylenol orange were found to be selective and sensitive for optical sensing of Al3+ in water. XO-AuNPs nanoparticles were characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS); the nanoparticles formed were of spherical shape and of uniform size of 3-12 nm. The interaction between Al3+ and XO-AuNPs at pH ~3 was studied by XPS analysis. XPS and TEM studies revealed that aggregation of XO-AuNPs in the presence of Al3+ takes place through analyte induced cross-linkage mechanism. Al3+ induced selective aggregation of the XO-AuNPs lead to a visual change in color of the colloidal solution from deep red to blue. The changes in characteristic absorption peak of XO-AuNPs were monitored; the ratio of A550nm/A515nm was used to quantify the concentration of Al3+ in water samples. The method gave a linear response from 50?300 ppb (R2 = 0.985) of Al3+ in drinking water with a detection limit of 12 ppb. The proposed method did not suffer any major interference from concomitant transition metal ions and anions. The developed method was simple, rapid and useful for determination of Al3+ in drinking water samples.
关键词： Aluminium,UV-visible spectroscopy,Optical sensor,Gold nanoparticles,X-ray photoelectron spectroscopy,Xylenol orange
更新于2025-09-16 10:30:52
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Investigation on Surface Properties of Mn-Doped CdSe Quantum Dots Studied by X-ray Photoelectron Spectroscopy
摘要： In this work, we report on the effects of incorporating manganese (Mn) dopant into different sizes of cadmium selenide (CdSe) quantum dots (QDs), which improves the electronic and optical properties of the QDs for multiple applications such as light-emitting diodes, lasers, and biological labels. Furthermore, the greener inverse Micelle method was implemented using organic ligand, which is oleic acid. This binding of the surface enhanced the QDs’ surface trap passivation of Mn-doped CdSe, which then increased the quantity of the output. In addition, the inverse Micelle technique was used successfully to dope Mn into CdSe QDs without the risk of Mn dopants being self-purified as experienced by wurtzite CdSe QDs. Also, we report the X-ray photoelectron spectroscopy (XPS) results and analysis of zinc blended manganese-doped cadmium selenide quantum dots (Mn-doped CdSe QDs), which were synthesized with physical sizes that varied from 3 to 14 nm using the inverse Micelle method. The XPS scans traced the existence of the Se 3d and Cd 3d band of CdSe crystals with a 54.1 and 404.5 eV binding energy. The traced 640.7 eV XPS peak is proof that Mn was integrated into the lattice of CdSe QDs. The binding energy of the QDs was related to the increase in the size of the QDs.
关键词： quantum dots,semiconductor,chemical synthesis,cadmium selenide,X-ray photoelectron spectroscopy,manganese doped
更新于2025-09-16 10:30:52
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Overcoming consistency constrains of ITO/ZnO/P3HT:PCBM/Ag solar cell by open air annealing and its systematic stability study under inborn conditions
摘要： Focusing on simplicity and industrial viability, polymer solar cells with configuration indium tin oxide (ITO)/ZnO/P3HT:PCBM/Ag were fabricated and characterized. Differing from the usual trend of using glove box for polymer device fabrication, here electron transport and active layer of the devices were deposited and stored in open air atmosphere without any encapsulation. Effect of active layer thickness on device performance was analyzed. Choosing the optimum thickness of 220 ± 20 nm, a number of devices were fabricated with same configuration and the effect of annealing on the photovoltaic parameters was investigated. Unlike annealing studies reported in literature, particular emphasis was given here to study the influence of annealing in ambient atmosphere, at temperature of 50 °C, for 30 s. This short period, low temperature annealing enhanced the device parameters mainly short circuit current density and hence efficiency. Lifetime measurements were done by monitoring the device and measuring its J–V parameters periodically for 1 year. X-ray photoelectron spectroscopy depth profile analysis was employed to demonstrate that surface modified ZnO effectively hinders the diffusion of indium from ITO to active layer.
关键词： Stability study,ITO/ZnO/P3HT:PCBM/Ag,X-ray photoelectron spectroscopy,Polymer solar cells,Open air annealing
更新于2025-09-12 10:27:22
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Local valence electronic states of silicon (sub)oxides on HfO2/Si-(sub)oxide/Si(110) and HfSi2/Si-(sub)oxide/Si(110) Islands
摘要： The effect on the local valence electronic states of Sin+ suboxide components (n = 2, 3, and 4) of hafnium deposited on a low-index Si(110) substrate is investigated by Si-L23VV Auger electron Sin+-2p photoelectron coincidence spectroscopy (Si-L23VV-Sin+-2p APECS), and the chemical states and stabilities are discussed. Hafnium-covered Si(110) is immediately oxidized to HfO2 and SiO2 because hafnium serves as an effective catalyst for Si oxidation. Therefore, a HfO2/Sin+-(sub)oxide/Si(110) [HfO2/Sin+/Si(110)] structure is easily formed (n = 1, 2, 3, and 4). Oxygen diffusion from HfO2 layers toward the Si(110) substrate is promoted by annealing at 923 K. Oxygen atom desorption from the HfO2/Sin+/Si(110) surface occurs after annealing at 1073 K, and HfSi2 islands (i-HfSi2) are formed with a partly exposed Si(110)-16 × 2 double domain (DD) surface. i-HfSi2 shows low reactivity toward O2 molecules, whereas the exposed Si(110)-16 × 2 DD surface is immediately oxidized. Here, a i-HfSi2/Sin+-(sub)oxide/Si(110) structure is formed. Furthermore, we measure the Si-L23VV-Sin+-2p APECS spectra of Sin+ in the HfO2/Sin+/Si(110) and the i-HfSi2/Sin+/Si(110) structures (n = 2, 3, and 4) to evaluate the local valence electronic states of the Sin+ (sub)oxide components. The binding energy at the valence band maximum (BEVBM) of Sin+ in the i-HfSi2/Sin+/Si(110) structure is lower than 1.5 ± 0.7 eV as compared to that in the HfO2/Sin+/Si(110) structure (n = 2, 3, and 4). The local valence electric states of the nearest neighbors and the second neighbors through oxygen of Sin+ are determined to affect those of the Sin+ atom (n = 2, 3, and 4). The Sin+ atoms in the i-HfSi2/Sin+/Si(110) structure can directly bond to hafnium atoms as the nearest neighbors and most commonly have Sim+ atoms in lower ionic valence states as second neighbors (m < 4), whereas the Sin+ atoms in the HfO2/Sin+/Si(110) structure cannot form this bond. In addition, the existence of Hf silicide and Si in lower ionic valence states can reduce the band gap of the HfO2/Si(110) structure.
关键词： High-dielectric-constant material,X-ray photoelectron spectroscopy,Local valence electronic states at surface and interface,Synchrotron radiation,Auger photoelectron coincidence spectroscopy,Metal-insulator-semiconductor structure
更新于2025-09-11 14:15:04
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Characterization of the Electronic Properties of Single‐Walled Carbon Nanotubes Filled with an Electron Donor—Rubidium Iodide: Multifrequency Raman and X‐ray Photoelectron Spectroscopy Studies
摘要： Single-walled carbon nanotubes (SWCNTs) with a mean diameter of 1.4 nm are filled with rubidium iodide. The filling of nanotubes is proved by high-resolution scanning transmission electron microscopy. The chemical composition of the filler is confirmed by X-ray photoelectron spectroscopy (XPS). The electronic properties of the filled SWCNTs are studied by XPS and Raman spectroscopy. The encapsulated salt leads to n-doping of nanotubes. The detailed multifrequency Raman spectroscopy investigation of the alteration of Raman modes of SWCNTs upon filling is conducted. The doping-induced changes in the radial breathing mode and G-band are revealed. It is found that these changes differ for the metallic and semiconducting SWCNTs. The obtained data and revealed trends are expected to be helpful for forthcoming studies to interpret the observed changes in Raman spectra of filled metallic and semiconducting SWCNTs.
关键词： Raman spectroscopy,electronic properties,X-ray photoelectron spectroscopy,rubidium iodide,filling,single-walled carbon nanotubes
更新于2025-09-11 14:15:04
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Formation of Highly Ordered Terminal Alkyne Self-Assembled Monolayers on the Au{111} Surface through Substitution of 1-Decaboranethiolate
摘要： The reaction aimed at completing and closing the open cages of 1-decaboranethiol self-assembled monolayers (SAMs) on Au{111} with 4-phenyl-1-butyne results in highly ordered monolayers of 4-phenyl-1-butyne. The initially disordered 1-decaboranethiolate changed into ordered (√3×√3)R 30° lattices on Au{111} typical of alkyne SAMs, indicating the complete substitution of 1-decaboranethiolate moieties, as determined by nanoscale imaging with scanning tunneling microscopy and X-ray photoelectron spectroscopy. Vibrational spectroscopy results indicate that the process happens gradually and that alkynyl groups are not totally oxidized in the ordered 4-phenyl-1-butyne monolayer.
关键词： Au{111},self-assembled monolayers,vibrational spectroscopy,scanning tunneling microscopy,X-ray photoelectron spectroscopy,4-phenyl-1-butyne,1-decaboranethiol
更新于2025-09-11 14:15:04
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Influence of the Cation on the Surface Electronic Band Structure and Magnetic Properties of Mn:ZnS and Mn:CdS Quantum Dot Thin Films
摘要： The effects of doping Mn into ZnS and CdS quantum dots are reported. Scanning tunneling spectroscopy spectra show a reduction in the electronic band gap in both CdS and ZnS upon incorporation of the Mn dopant. Mn:ZnS exhibits a rigid band shift toward higher bias which is reminiscent of a hole doping effect. This rigid band shift in Mn:ZnS is argued, with the help of X-ray photoelectron spectroscopy, to be due to a hole-doping mechanism caused by the favorable formation of Zn vacancies and a reduction in S vacancies compared to undoped ZnS films. In CdS no rigid band shift is observed even though the presence of Cd vacancies can be confirmed by photoemission and magnetic measurements. A strong sp-d hybridization is observed in the Mn:CdS film upon introducing the Mn dopant. d0 ferromagnetism is observed in both undoped ZnS and CdS quantum dot thin films at room temperature. Upon doping of Mn into ZnS the magnetization is reduced suggesting an antiparallel alignment of Mn-Mn or Mn-Zn vacancies nearest neighbors. Density Functional Theory supports the experimental results indicating the nearest neighbor Mn atoms prefer antiparallel alignment of their magnetic moments with preferred ground state of Mn in 3+ oxidation state.
关键词： CdS,Mn doping,quantum dots,magnetic properties,scanning tunneling spectroscopy,electronic band structure,X-ray photoelectron spectroscopy,density functional theory,ZnS
更新于2025-09-11 14:15:04
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Influence of oxygen vacancy on the response properties of TiO2 ultraviolet detector
摘要： In this paper, the effect of sputtering distance between target and substrate (DTS) on the structural, morphological and optical properties of TiO2 films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that crystallite size and surface morphology were strongly dependent on DTS. The X-ray photoelectron spectroscopy (XPS) results showed that obvious three peaks including C1S, Ti2p and O1s could be clearly observed and binding energy was 285, 458 and 531 eV, respectively. For each sample, four peaks at about 386, 462, 527 and 595 nm in photoluminescence (PL) spectrum were observed and produced by intrinsic recombination, F center, F+ center and electrons transferred from 3d Ti3+ states to the deep levels OH?, respectively. Finally, photoresponse properties of UV detector based on TiO2 films were further analyzed and TiO2 UV detector prepared by DTS of 80 mm showed a high responsivity of 2.02 ×10-4 A/W and photosensitivity of 32.25, also, exhibited a fast response with a rise time (τr) of 0.98 s and fall time (τf) of 3.14 s.
关键词： UV detector,oxygen vacancy,TiO2 thin films,X-ray photoelectron spectroscopy
更新于2025-09-11 14:15:04
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Vacuum-UV of polyetheretherketone (PEEK) as a surface pre-treatment for structural adhesive bonding
摘要： Polyetheretherketone (PEEK) is known for its poor wettability and poor adhesive properties. Hence, for the creation of reliable high-strength structural adhesive bonded joints, surface treatment of PEEK is required. In this work high strength bondable PEEK surfaces were achieved through a vacuum-UV (VUV) treatment. Samples of amorphous and semi-crystalline PEEK films were exposed to different VUV radiation doses. Additionally oxygen low-pressure plasma (LPP) and untreated (as received) PEEK samples were investigated for comparison. Surfaces were characterized using x-ray photoelectron spectroscopy (XPS), contact angle measurements (CA), atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). Tensile tests of the PEEK films were carried out, to investigate changes in the mechanical properties in the bulk of the PEEK films due to the VUV exposure. The adhesive bond strength of treated specimen was determined through two different test methods (tensile and shear). These strengths were compared to the created surface properties. A strong correlation between the contact angle and the creation of functional groups was observed. VUV radiation appears as a suitable pre-treatment method for PEEK, as adhesive bonds of high strength were achieved after 5 seconds. Additionally, the usage of a VUV excimer lamp is simple, cheap and easy for automation.
关键词： X-ray photoelectron spectroscopy,Vacuum-UV (VUV),contact angles,chemical surface functionalization,structural adhesive bonding,Polyetheretherketone (PEEK),atomic force microscopy
更新于2025-09-11 14:12:44