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- 2018
- tumor imaging
- conductivity
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- Electrical properties tomography
- Optoelectronic Information Science and Engineering
- Ghent University
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Structural and optical properties of a revived Pb0.5Ba1.5BiVO <sub/>6</sub> perovskite oxide
摘要： The polycrystalline ceramic Pb0:5Ba1:5BiVO6 manifesting the complex double perovskite structure was tailored by the conventional solid state route at a moderate temperature. Qualitative phase analysis and formation of the ceramic were affirmed by XRD analysis. The X-ray powder diffraction pattern of the compound explored at room temperature affirms the single phase formation with double perovskite structure exhibiting rhombohedral phase. Microstructural analysis of the studied compound procured from the Scanning Electron Microscope (SEM) validates the formation of dense microstructures and nonuniformly distributed grains with minimal voids. Compositional analysis was shaped through the Electron Diffraction Spectroscopy (EDS) confirming the absence of contamination of any other metals apart from the mentioned ones. Dielectric (Cr and tan δ) parameters of the compound were studied using the LCR analyzer at different temperatures and wide range of frequencies. The polarization and dielectric study affirms the presence of ferroelectricity in the material with transition temperature much above the room temperature. The tangent dielectric loss of this sample being almost minimal at room temperature attributes it to find applications in different grounds of electronics. Optical equities of the ceramic were further analyzed by the RAMAN, FTIR, UV–Vis and Photoluminescence spectroscopy.
关键词： EDS,Ceramic,X-Ray diffraction,LCR,optical properties
更新于2025-11-14 14:48:53
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Dynamically Switching the Electronic and Electrostatic Properties of Indium Tin Oxide Electrodes with Photochromic Monolayers: Toward Photo-Switchable Optoelectronic Devices
摘要： The chemical modification of electrodes with organic materials is a common approach to tune the electronic and electrostatic landscape between interlayers in optoelectronic devices, thus facilitating charge injection at the electrode/semiconductor interfaces and improving their performance. The use of photochromic molecules for the surface modification allows dynamic control of the electronic and electrostatic properties of the electrode and thereby enables additional functionalities in such devices. Here, we show that the electronic properties of a transparent indium tin oxide (ITO) electrode are reversibly and dynamically modified by depositing organic photochromic switches (diarylethenes) in the form of self-assembled monolayers (SAMs). By combining a range of surface characterization and density functional theory calculations, we present a detailed picture of the SAM binding onto ITO, the packing density of molecules, their orientation, as well as the work function modification of the ITO surface due to the SAM deposition. Upon illumination with ultraviolet and green light, we observe a reversible shift of the frontier occupied levels by 0.7 eV, and concomitantly a reversible work function change of ca. 60 meV. Our results prove the viability of dynamic switching of the electronic properties of the electrode with external light stimuli upon modification with a monolayer of photochromic molecules, which could be used to fabricate ITO-based photo-switchable optoelectronic devices.
关键词： self-assembled monolayer,diarylethene,ITO,photochromic switch,interface electronic properties
更新于2025-11-14 14:32:36
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Plastic anisotropy of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe titanium alloy
摘要： Tensile tests of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe titanium alloy specimens in different orientations were conducted, which indicates significant plastic anisotropy of this material. Digital image correlation method added in-situ-tensile tests were carried out to investigate mechanical properties with respect to specified material structures. The results indicate that the plasticity properties of the thick columnar grain and that of other grains are significant different. Under the same stress level, the thick columnar grain yield firstly and bear the main plastic deformation of the whole specimen. The elasto-plastic Poisson's ratio of the thick columnar grains and that of other grains are also different. Tests on layer bands indicate that the coarser microstructures of the layer bands lead a stronger resistance to tensile plastic deformation, but a weaker resistance to shear plastic deformation. In addition, the direction of primary α laths on both sides of the layer bands may be different, and this has an obviously effect on the tensile plastic deformation of the specimen.
关键词： Digital image correlation method,Plastic anisotropy,Laser melting deposited,Titanium alloy,Mechanical properties
更新于2025-10-24 16:40:20
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AlN-based hybrid thin films with self-assembled plasmonic Au and Ag nanoinclusions
摘要： Aluminum nitride (AlN)-based two-phase nanocomposite thin films with plasmonic Au and Ag nanoinclusions have been demonstrated using a one-step thin film growth method. Such AlN-based nanocomposites, while maintaining their wide bandgap semiconductor behavior, present tunable optical properties such as bandgap, plasmonic resonance, and complex dielectric function. Depending on the growth atmosphere, the metallic nanoinclusions self-organized into different geometries, such as nano-dendrites, nano-disks, and nanoparticles, providing enhanced optical anisotropy in-plane and out-of-plane. The infrared transmission measurements demonstrate the signature peaks of AlN as well as a broad transmission window attributed to the plasmonic nanoinclusions. This unique AlN-metal hybrid thin film platform provides a route to modulate the optical response of wide bandgap III-V nitride semiconductors towards infrared sensing or all optical based integrated circuits.
关键词： plasmonic Au and Ag nanoinclusions,infrared sensing,integrated circuits,AlN-based hybrid thin films,optical properties
更新于2025-10-22 19:40:53
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Effects of fluorination and thermal annealing on charge recombination processes in polymer bulk-heterojunction solar cells
摘要： We investigate the effect of fluorination on the photovoltaic properties of an alternating conjugated polymer composed of 4,8-di-2-thienylbenzo[1,2-b:4,5-b0]dithiophene and 4,7-bis([2,20-bithiophen]-5-yl)-benzo-2-1-3-thiadiazole (4TBT) units in bulk-heterojunction solar cells. The unsubstituted and fluorinated polymers afford very similar open-circuit voltages and fill factor values, but the fluorinated polymer performed better due to enhanced aggregation which provides a higher photocurrent. The photovoltaic performance of both materials improved upon thermal annealing at 150–200 °C as a result of a significantly increased fill factor and open-circuit voltage, counteracted by a slight loss in photocurrent. Detailed studies of the morphology, light intensity dependence, external quantum efficiency and electroluminescence allowed the exploration of the effects of fluorination and thermal annealing on the charge recombination and the nature of the donor–acceptor interfacial charge transfer states in these films.
关键词： polymer bulk-heterojunction solar cells,thermal annealing,charge recombination,fluorination,photovoltaic properties
更新于2025-10-22 19:40:53
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Enhancing light absorption by colloidal metal chalcogenide quantum dots <i>via</i> chalcogenol(ate) surface ligands
摘要： Chemical species at the surface (ligands) of colloidal inorganic semiconductor nanocrystals (QDs) markedly impact the optoelectronic properties of the resulting systems. Here, post-synthesis surface chemistry modification of colloidal metal chalcogenide QDs is demonstrated to induce both broadband absorption enhancement and band gap reduction. A comprehensive library of chalcogenol(ate) ligands is exploited to infer the role of surface chemistry on the QD optical absorption: the ligand chalcogenol(ate) binding group mainly determines the narrowing of the optical band gap, which is attributed to the np occupied orbital contribution to the valence band edge, and mediates the absorption enhancement, which is related to the π-conjugation of the ligand pendant moiety, with further contribution from electron donor substituents. These findings point to a description of colloidal QDs that may conceive ligands as part of the overall QD electronic structure, beyond models derived from analogies with core/shell heterostructures, which consider ligands as mere perturbation to the core properties. The enhanced light absorption achieved via surface chemistry modification may be exploited for QD-based applications in which an efficient light-harvesting initiates charge carrier separation or redox processes.
关键词： colloidal metal chalcogenide quantum dots,light absorption,optoelectronic properties,surface ligands,band gap reduction
更新于2025-10-22 19:40:53
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New copolymer involving PVK and F8BT for organic solar cells applications: Design, synthesis, characterization and theoretical studies
摘要： The new PVK-F8BT copolymer coupled to poly (9-vinylcarbazole) and poly(9,9-dioctyl?uorene-alt-benzothiadiazole) has been designed and elaborated by chemical oxidation for organic solar cells applications. Structural and photophysical properties were examined using di?erent and complementary techniques (Infrared, optical absorption, stationary and time resolved photoluminescence). The PVK-F8BT exhibited a broad absorption band covering the wavelength range from 200 nm to 700 nm covering the solar spectrum and, highlighting the charge transfer process. Moreover, the PVK-F8BT, showed a low band gap to be found to 1.9 eV and it average lifetime (2.62 ns) are longer than that of F8BT. The resulting copolymer exhibits original optical properties compared to the PVK and F8BT ones. The experimental analyses were coupled to theoretical calculations based on density functional theory and time-dependant density functional theory methods in order to better understand the structure-properties correlation. Furthermore DFT and TD-DFT calculations of the PVK-F8BT have been exploited to optimize the copolymer-based composites based on bulk heterojunction based organic photovoltaic copolymers with the 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]–C61, as an acceptor. Thus, the band gap decreased to 1.69 eV, the power energy conversion e?ciency was about 7%. Our results have allowed us to discover a promising new photovoltaic material.
关键词： TD-DFT,Optical properties,Solar cells,Donor-acceptor,Charge transfer
更新于2025-10-22 19:40:53
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Structural, electronic and optical properties of pulsed laser deposited Cu2SnS3 photo absorber thin films: A combined experimental and computational study
摘要： Pulsed laser deposited thin films of Cu2SnS3 (CTS) are characterized for the structural, electronic and optical properties using X-ray diffraction, Raman, UV–Vis-NIR spectroscopy, scanning electron microscopic techniques, and density functional theory. It is observed that thin-film samples annealed at low temperature have a metastable tetragonal structure, whereas the films annealed at 450 °C have a predominant stable monoclinic phase. A direct band gap of 1.1 eV, measured from the transmittance spectra, in close agreement with the theoretical band gap value of 0.89 eV obtained from density functional theory calculations. Optical properties reveal that CTS has a large absorption coefficient ~0.5 × 104 cm?1 at 1.5 eV which is comparable to other CuS based materials like CuInS2 and Cu2ZnSnS4. The direct band gap and large absorption coefficient make CTS as one of the potential alternative absorber materials for thin-film solar cell applications.
关键词： Annealing,Raman spectroscopy,Thin films,Density functional theory,Pulsed laser deposition,Optical properties
更新于2025-10-22 19:40:53
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Effect of Substrate Temperature on Properties of Nickel Oxide (NiO) Thin Films by Spray Pyrolysis
摘要： NiO thin films were deposited on a glass substrate and investigated for the physical properties optimized through substrate temperature (350–390°C) using a spray pyrolysis technique. The effect of substrate temperature on deposited NiO thin film was studied by thermogravimetric analysis and differential thermal analysis, X-diffraction (XRD), field electron scanning electron microscopy, optical absorption and electrical measurement techniques. XRD analysis indicates that NiO thin films are of a polycrystalline cubic structure. Optical properties are calculated with help of transmittance and absorbance data in the wavelength range between 200 nm and 900 nm. The optical band gap energy values increased from 3.1 eV to 4.0 eV with substrate temperature. Further, the extinction coefficient, refractive index, and real and imaginary parts of dielectric constant and optical conductivities of NiO thin films were calculated. The electrical resistivity measurement shows conductivity of the NiO thin film increased with increase in substrate temperature.
关键词： composition,spray,semiconducting behavior,electrical properties,NiO
更新于2025-10-22 19:40:53
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An investigation of 60Co gamma radiation-induced effects on the properties of nanostructured α-MoO3 for the application in optoelectronic and photonic devices
摘要： Gamma ray has sufficient energy to ionize and displace of atoms when interacts with optoelectronic and photonic devices that are placed at γ-radiation exposure environment, can be exposed to gamma radiation, resulting the alteration of the physical properties and hence the performances of devices. A comprehensive investigation of physical properties of the semiconductor materials under the influence of gamma radiation is essential for the effective design of devices for the application in the radiation exposure environment. In this article, a potential candidate for optoelectronic and photonic devices, orthorhombic MoO3 nanoparticles with average crystallite size of 135.31 nm successfully synthesized by hydrothermal method. Then, the properties of nanoparticles exposed to low (10 kGy) and high (120 kGy) absorbed dose of γ-rays from 60Co source were characterized by XRD, FESEM, FTIR and UV–Vis–NIR spectrophotometer and effects of absorbed doses was investigated for the first time. A significant change is observed in different physical properties of α-MoO3 nanoparticles after gamma exposure. The XRD patterns reveal the average crystallite size, intensity and the degree of crystallinity decrease for low dose (10 kGy) and increases for high dose (120 kGy). The calculated average crystallite size exposed to low and high doses are 127.79 nm and 136 nm, respectively. The lattice strain and dislocation density, however, shows the opposite trend of crystallite size with absorbed doses. This result is good evidence for the deterioration of crystallinity for low dose and improvement for high dose. The FESEM results reveal the significant effects of gamma doses on the micrographs of layered structure and on grain size. The optical studies disclose that band gap increases gradually from 2.78 to 2.90 eV, this behavior is associated with the reduction of electronic localized states. These results suggest that α-MoO3 nanoparticles could tolerate high doses of gamma radiation, making it a promising candidate for optoelectronic and photonic devices for γ-ray exposure environment applications.
关键词： Optoelectronic and photonic devices,α-MoO3 nanoparticles,Co-60 gamma radiation,Optical bandgap,Structural properties
更新于2025-10-22 19:40:53