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Photovoltaic performance improvement via designing nanorod parameter in composite-structure solar cells
摘要： In this work, the optical characteristics of electrodeposited Cu2O films was studied, and the depth of photogenerated carriers in Cu2O films was obtained. In order to improve the collection depth of the photogenerated carrier in ZnO/Cu2O solar cells, ZnO nanorod array were employed to construct composite-structure solar cells. The influence of the ZnO nanorod arrays on short-circuit current and open circuit voltage was systematically analyzed in the nanorod cells. For optimizing device performance, ordered ZnO nanorod arrays that incorporated design spacing that matched the carrier diffusion length of the absorption layer were used. Analyses of the photovoltaic properties revealed that ordered nanorod arrays with a proper spacing could improve carrier generation efficiency in high-efficient collection regions of the carriers. These observations indicate that nanorod spacing is an important variable in the construction of high-efficient nanorod-based solar cells.
关键词： Radial heterojunction,Carrier collection length,Optical absorption depth,Ordered ZnO nanorod array
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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Confined electron states in two-dimensional HgTe in magnetic field: Quantum dot versus quantum ring behavior
摘要： We investigate the electron states and optical absorption in square- and hexagonal-shaped two-dimensional (2D) HgTe quantum dots and quantum rings in the presence of a perpendicular magnetic field. The electronic structure is modeled by means of the sp3d 5s? tight-binding method within the nearest-neighbor approximation. Both bulklike and edge states appear in the energy spectrum. The bulklike states in quantum rings exhibit Aharonov-Bohm oscillations in magnetic field, whereas no such oscillations are found in quantum dots, which is ascribed to the different topology of the two systems. When magnetic field varies, all the edge states in square quantum dots appear as quasibands composed of almost fully flat levels, whereas some edge states in quantum rings are found to oscillate with magnetic field. However, the edge states in hexagonal quantum dots are localized like in rings. The absorption spectra of all the structures consist of numerous absorption lines, which substantially overlap even for small line broadening. The absorption lines in the infrared are found to originate from transitions between edge states. It is shown that the magnetic field can be used to efficiently tune the optical absorption of HgTe 2D quantum dot and quantum ring systems.
关键词： HgTe,quantum dots,quantum rings,optical absorption,electron states,tight-binding method,magnetic field,Aharonov-Bohm oscillations
更新于2025-09-12 10:27:22
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Pr3+-Doped Strontium–Aluminum–Bismuth–Borate Glasses for Laser Applications
摘要： The chemical composition of Pr3+-doped strontium–aluminum–bismuth–borate glasses with different concentrations, that is, (50 – x)B2O3 + 20Bi2O3 + 7AlF3 + 8SrO + 15SrF2 + xPr2(CO3)3 (where x = 0.1, 0.5, 1.0, and 1.5 mol.%), have been prepared by the melt quenching technique. XRD, SEM, and EDS studies reveal the structural and amorphous properties of the prepared glasses. Different borate groups are analyzed by FTIR measurements. Judd–Ofelt (J–O) intensity parameters, Ωλ (λ = 2, 4, and 6) are calculated from the absorption spectrum to identify the nature of Pr3+ ions with their surrounding ligands. Using the J–O parameters, the radiative properties such as radiative transition probabilities AR and radiative lifetimes τcal are evaluated for various excited transitions of Pr3+ ions. Stimulated emission cross sections σpE and branching ratios βR for the emission transitions are evaluated by the photoluminescence spectra. The higher values of σpE and βR are identified for the emission transitions 3P0 → 3H4 and 1D2 → 3H4 of SABiBPr15 and SABiBPr01 glasses; these glasses are suitable for light emitting materials. The chromaticity color coordinates are calculated to find the average color of the emission spectra.
关键词： Judd–Ofelt analysis,optical absorption,photoluminescence,praseodymium
更新于2025-09-12 10:27:22
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Photodetectors [Working Title] || Overcoming the Bandwidth-Quantum Efficiency Trade-Off in Conventional Photodetectors
摘要： Optical systems and microwave photonics applications rely heavily on high-performance photodetectors having a high bandwidth-efficiency product. The main types of photodetector structures include Schottky and PIN-photodiodes, heterojunction phototransistors, avalanche photodetectors, and metal-semiconductor-metal photodetectors. Vertically-illuminated photodetectors intrinsically present bandwidth-efficiency limitations, but these have been mitigated by new innovations over the years in quantum well photodetectors, edge-coupled photodetectors and resonant-cavity enhanced photodetectors for improved photophysical characteristics. Edge-coupled ultra-high-speed photodetectors have yielded high conversion efficiencies, and the active device structure of resonant-cavity-enhanced photodetectors allows wavelength selectivity and optical field enhancement due to resonance, enabling photodetectors to be made thinner and hence faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. Single-photon avalanche diodes have been developed, which combine an ultimate sensitivity with excellent timing accuracy. Further advances in addressing the bandwidth-quantum efficiency trade-off have incorporated photon-trapping nanostructures and plasmonic nanoparticles. Nanowire photodetectors have also demonstrated the highest photophysical performance to date.
关键词： photosensitivity,saturation current,quantum efficiency,optical absorption,drift layers,bandwidth-efficiency product
更新于2025-09-12 10:27:22
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Creation of Si quantum dots in a silica matrix due to conversion of radiation defects under pulsed ion-beam exposure
摘要： In this work we present an innovative method of creating Si quantum dots under pulsed ion-beam exposure. The evolution of defect structure ODC(II) - E0 - ODC(I) - Si QDs in glassy SiO2 under ion-beam implantation was established by optical absorption and photoluminescence spectroscopies. Depending on the mode of ion exposure, it is possible to easily control the type and concentration of defects in the host and modify its optical properties for novel applications. Ab initio calculations confirm that bond softening in SiO2 is attainable via the use of Gd ion implantation. According to our experimental and theoretical results, the three-stage interaction of primary oxygen-deficient centers leads to the formation of stable silicon quantum dots with a size of 3.6 nm and luminescence at 1.8 eV excited by incoherent light.
关键词： Gd ion implantation,Si quantum dots,pulsed ion-beam exposure,optical absorption,photoluminescence spectroscopies,glassy SiO2
更新于2025-09-12 10:27:22
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Nonfullerene Small-Molecule Acceptors with Extended Optical Absorption Based on the “Spliced” Strategy for Organic Solar Cells
摘要： How to broaden the optical absorption of photovoltaic materials is one of the key issues in the design of high-performance organic solar cells. Nowadays, the sunlight of 400–550 nm wavelength range is not effectively utilized for most small-molecule nonfullerene acceptors. In this work, we proposed the “spliced” strategy of combining the acceptor–donor–acceptor type narrow band-gap small molecules and wide-band-gap perylene diimide (PDI) moieties via a flexible alkyl chain linkage, which could give the superposition effect of the absorption spectra, and three small-molecule acceptors (S1, S2, and S3) were designed based on various end-capping groups with different electron withdrawing abilities. Encouragingly, the as-constructed molecules can well make use of 400–550 nm sunlight with two independent absorption regions. Meanwhile, the aggregation of S1 with a highly planar end-capping group was dominated by both the PDI unit and main skeleton, while S2 and S3 exhibited PDI-controlled aggregation. When fabricated into organic solar cells, S1-based devices achieved a superior efficiency of 3.41% in comparison with those of the other two. The poor photovoltaic performance could be attributed to severe PDI aggregation, which can hinder the charge transfer through the main skeletons. This work could provide a new perspective to modulate optical absorption through the spliced strategy.
关键词： Organic solar cells,spliced strategy,aggregation,optical absorption,nonfullerene acceptor
更新于2025-09-12 10:27:22
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Dot size variability induced changes in the optical absorption spectra of interdiffused quantum dot systems
摘要： In this work, we have quantified the effects of dot size variability on the interband optical absorption spectra of interdiffused III–V quantum dot (QD) systems through analytical models which agree well with experimental data. The variability function induced due to inhomogeneous nature of dot size distribution has been considered to be Gaussian in nature, where individual dots have been assumed to be lens-shaped having inhomogeneous material composition inside the dot. This is necessary to consider any realistic interdiffused system. Such an assumption is not in line-up with the conventional methodologies reported earlier on the subject, where the QD composition was considered to be homogeneous, presenting an ideal or quasi-ideal situation which may be applicable only for dot structures in absence of interdiffusion. Moreover, for the first time, the effects of dot size variability and interdiffusion on the optical spectra of QD systems have been analysed in the same platform. The effects of dot size deviation, QD aspect ratio, core group III content inside the dot, standard deviation, and so on, on the optical absorption spectra have been demonstrated.
关键词： Dot size variability,III–V semiconductors,Optical absorption spectra,Interdiffusion,Quantum dots
更新于2025-09-11 14:15:04
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Enhancing Nonradiative Energy Transfer between Nitridized Carbon Quantum Dots and Monolayer WS2
摘要： Two-dimensional (2D) monolayer (1L) transition metal dichalcogenides (TMDs) suffer from a low absorption in the visible light region. Nonradiative energy transfer (NRET) is an effective method to enhance such absorption, which, as shown in this study, can be accomplished by using surface nitridized carbon quantum dots (CQDs). The optical absorption and photoluminescence (PL) of CQDs in the visible light region can be greatly enhanced by increasing the level of nitridization. The nitridized CQDs exhibit weak p-type doping but strong PL quenching in contact with vapor transport (VT)-deposited 1L-WS2. Owing to the good overlap between the fluorescence and absorption spectra for CQDs and 1L-WS2, an interactive NRET process reduces the PL lifetimes of both CQDs and 1L-WS2. The NRET efficiency can be greatly enhanced by up to 73% for samples coated with CQDs of increasing surface nitridization.
关键词： Nonradiative energy transfer,Nitridized carbon quantum dots,Optical absorption,Monolayer WS2,Photoluminescence
更新于2025-09-11 14:15:04
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A flexible control on electromagnetic behaviors of graphene oligomer by tuning chemical potential
摘要： In this work, we demonstrate that the electromagnetic properties of graphene oligomer can be drastically modified by locally modifications of the chemical potentials. The chemical potential variations of different positions in graphene oligomer have different impacts on both extinction spectra and electromagnetic fields. The flexible tailoring of the localizations of the electromagnetic fields can be achieved by precisely adjusting the chemical potentials of the graphene nanodisks at corresponding positions. The proposed nanostructures in this work lead to the practical applications of graphene-based plasmonic devices such as nanosensing, light trapping and photodetection.
关键词： Graphene oligomer,Electromagnetic tunability,Surface plasmon,Optical absorption
更新于2025-09-11 14:15:04