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Defect analysis of TiO2 doped with ytterbium and nitrogen by ab initio calculations
摘要： Different defects are studied in the network of anatase TiO2 to improve the utilization of the material for photoelectrochemical applications. With the ab initio calculations, defect-induced TiO2 models with different doping concentrations and oxidation states of Yb and N dopants are studied. Oxygen-deficient systems are modeled, and the interaction of oxygen vacancy with the Yb and N dopant in the bulk of TiO2 is elucidated. Yb 4f states are coupled with the O 2p states reducing the band gap and shifting the absorption edge of the TiO2 toward visible regime. Increasing Yb doping concentration reduced the band gap, and the 2.08% Yb doping concentration is considered as an optimal Yb doping. Comparing the band structures of mono-doped and codoped samples, Yb, N codoping reduced the band gap while creating isolated states in the forbidden region. Compensated and non-compensated systems of Yb- and/or N-doped TiO2 models are studied. Charge compensation in Yb, N-codoped TiO2 stabilized the system, reduced the band gap without having isolated states and provided broader absorption band. The Ti16?xYbxNyO31?y, x = 2, y = 1, model provided minimum structure modification with the suitable band structure for photoelectrochemical applications explaining the experimental results for the synergistic effect of Yb, N codoping in TiO2.
关键词： Doping concentration,Point defects,Charge compensation,Ytterbium
更新于2025-09-23 15:23:52
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The Investigation of the Seebeck Effect of the Poly(3,4-Ethylenedioxythiophene)-Tosylate with the Various Concentrations of an Oxidant
摘要： Poly(3,4-ethylenedioxythiophene)-tosylate (PEDOT-Tos) can be synthesized through an in situ polymerization and doping process with iron(III) p-toluenesulfonate hexahydrate as an oxidant. Both the Seebeck coefficient and the electrical conductivity were modified by varying the concentration of the oxidant. We investigated the effects of varying the concentration of the oxidant on the particle sizes and doping (oxidation) levels of PEDOT-Tos for thermoelectric applications. We demonstrated that an increase in the oxidant enabled an expansion of the particle sizes and the doping levels of the PEDOT-Tos. The modification of the doping levels by the concentration of the oxidant can provide another approach for having an optimal power factor for thermoelectric applications. De-doping of PEDOTs by reduction agents has been generally investigated for changing its oxidation levels. In this study, we investigated the effect of the concentration of the oxidant of PEDOT-Tos on the oxidation levels, the electrical conductivities and the Seebeck coefficients. As loading the oxidant of PEDOT-Tos, the Seebeck coefficient was compromised, while the electrical conductivity increased.
关键词： conjugated polymer,doping concentration,seebeck effect
更新于2025-09-23 15:22:29
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THz cutoff frequency and multifunction Ti 2Ba2Ca2Cu3O10/GaAs photonic bandgap materials
摘要： By using the transfer matrix method (TMM), we theoretically explore the transmittance properties and cuto? frequency of one-dimensional photonic crystal (1DPCs) within the terahertz frequency region. The present structure consists of high-temperature superconductor and semiconductor layers. The results of the calculations represent the e?ects of various parameters on the cuto? frequency. We have used the two-?uid model as well as the Drude model to describe the permittivity of superconductor and semiconductor. Further, we consider that the permittivity of both the materials is depending on the hydrostatic pressure. The present results show that with the increasing of di?erent parameters as the operating temperature, the thickness of semiconductor, and the ?lling factor of semiconductor, then the cuto? frequency shift to lower frequencies regions. By the increasing of superconductor thickness, hydrostatic pressure, doping concentration and ?lling factor of the superconductor, we found the cuto? frequency shifts to higher frequency regions. These results indicate that cuto? frequency can be modi?ed through these di?erent parameters. Finally, the present design could be useful for many optical systems as the optical ?lter, re?ector and photoelectronic applications in the Terahertz regime.
关键词： Cuto? frequency,transfer matrix method,photonic crystal,doping concentration,hydrostatic pressure,two-?uid model,Drude model
更新于2025-09-23 15:21:01
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Nonresonant Polarized Raman Spectra Calculations of Nitrogen-Doped Single-Walled Carbon Nanotubes: Diameter, Chirality, and Doping Concentration Effects
摘要： Raman spectra of nitrogen-doped single-walled carbon nanotubes are calculated using the spectral moment’s method combined with the bond polarizability model. The influence of the nanotube diameter and chirality is investigated. We also address the important question of the effect of the N-doping concentration, and we propose an equation to estimate the doping concentration from the knowledge of the tube diameter and the frequency of the radial breathing mode.
关键词： spectral moment’s method,Raman spectra,N-doping concentration,nanotube diameter,nitrogen-doped single-walled carbon nanotubes,bond polarizability model,chirality
更新于2025-09-23 15:21:01
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Decent efficiency improvement of organic photovoltaic cell with low acidic hole transport material by controlling doping concentration
摘要： Presently, poly (3, 4-ethylenedi-oxythiophene): polystyrene sulfonic acid (PEDOT:PSS) is most commonly used hole transport material (HTM) in photovoltaic (PV) cells but its higher acidity, hygroscopicity, high price have motivated people to develop a good substitute. Here, we prepare a series of PSS-doped polyaniline (PANI) with synergic (around 90%) transmittance and work function value (within 5.09-5.16 eV) varying PSS concentrations to check the possible utility as HTM in a poly (3-hexylthiophene): [6, 6]-indene-C60 bisadduct based organic photovoltaic (OPV) cell. Here, it is observed that, because of change in conductivity, the PV performance of those OPV devices is strongly dependent on the doping concentration of the HTM and, at optimized PSS concentration, PANI:PSS has higher conductivity. This facilitates better hole extraction efficiency into the PV device and results in higher short circuit current density (JSC). Therefore, the PANI:PSS-based OPV device with optimized PSS concentration exhibits same level of power conversion efficiency (PCE: 4.5±0.2 %) as a PEDOT:PSS based OPV device. Thus, a lower acidic (pH = 2.2) p-type semiconductor PANI:PSS (weight ratio = 1:1 and) can be a good alternative to highly acidic (pH = 1.7) PEDOT:PSS ( weight ratio = 1:6, Clevious Al 4083) for using as HTM in an OPV device.
关键词： Hole transport layer,Organic photovoltaic cell,Doping concentration,Poly (4-styrenesulfonic acid) doped poly (3, 4-ethylenedi-oxythiophene),Poly (4-styrenesulfonic acid) doped polyaniline
更新于2025-09-23 15:19:57
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Chemical Bonding States and Dopant Redistribution of Heavily Phosphorus-doped Epitaxial Silicon Films: Effects of Millisecond Laser Annealing and Doping Concentration
摘要： We investigated the effect of millisecond (ms) laser annealing and doping concentration on the chemical bonding states and dopant behaviors of P-doped epitaxial Si (Si:P) layers grown on Si (100) substrates using high-resolution X-ray photoelectron spectroscopy (HR-XPS), secondary-ion mass spectroscopy (SIMS) and Auger electron spectroscopy (AES) measurements. Our XPS results showed that the intensities of P 2p peaks for Si:P films were increased with P concentration and subsequent laser annealing. From the SIMS and AES measurement results, we found that P atoms were slightly accumulated at the near-surface region of the Si:P film by the laser annealing, while macroscopic P concentration being maintained in the whole Si:P films without significant diffusion of P atoms toward the Si (100) substrate. In addition, we performed ex-situ HF cleaning on the as-grown and laser-annealed Si:P films in order to precisely measure the change in chemical states and dopant distribution at the near-surface region. The intensities of the P 2p peak in the as-grown Si:P films were increased after the HF cleaning due to the removal of native oxide layers from the Si:P films. In contrast, the decrease in P 2p peak intensities was observed in the laser-annealed Si:P films after the HF cleaning, indicating the dopant loss from the near-surface region with native oxide removal.
关键词： Millisecond laser annealing,Dopant redistribution,Chemical bonding states,Phosphorus-doped epitaxial silicon films,Doping concentration
更新于2025-09-19 17:13:59
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A new method to enhance organic photodetectors active layer trap doping by blending doping
摘要： In order to solve the problem of high concentration trap doping in the active layer of organic detector, a blending doping method is proposed in this paper. The influence of the doping concentration of C60:C70 on the trap concentration in the P3HT:PC61BM active layer and the optoelectronic performance of the detector are studied through experiments. It founds that the maximum doping concentration and trap concentration of active layer could arrive to 1.5 wt.% and 3.26×1018 cm-3 respectively after blending doping, which increased by 50% and one order of magnitude compared with the maximum doping concentration of single C60(doping concentration:1.0wt.%, trap concentration: 5.83×1017 cm-3), and the external quantum efficiency is increased by 8 folds from 1067.84% to 8510.17%. The result shows that the doping concentration and the trap concentration can be greatly improved using the blending doping method, and thereby the high concentration trap doping of the active layer can be achieved.
关键词： high doping concentration,blending doping,organic photodetectors
更新于2025-09-12 10:27:22
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Modeling and optimization of n-c-AlGaAs/p-c-GaAs solar cells
摘要： The main of our work is to establish a model which enables us to predicate an improvement for solar cells e?ciencies elaborated by hetero-structures compounds; we focused our optimization by simulation on an n-c-AlGaAs/p-c-GaAs solar cell with back surface ?eld (BSF), which is a p/p+ (Low-High) junction. This junction creates a potential barrier which avoid speedy recombination of minor careers (electron in the base), however all the main parameters which have large impact on the short circuit current density, on the open circuit voltage, on the ?ll factor and on the conversion e?ciency were discussed in this work. Generally the electrical conversion is function of the acceptor and donor doping concentrations, of the cell emitter and the base thicknesses, of the surface recombination velocity at front and back contacts and of careers live times (for electrons and holes). The e?ects of the discontinuities occurring in the energies bands clause to the interface were taken into consideration too. Under A.M 1.5 illumination, our calculations results reveal an e?ciency of 23.80% for the optimum parameters (Nd = 5 × 1018 cm?3, Na = 5 × 1017 cm?3, JSC = 25.77 mA/cm2, VOC = 0.985 V, Sf = 104 cm/s and Sb = 108cm/s). It seems that this simulated device can be used in cell concentrations utilities and, it presents an e?ciency of 29.28% under 100 A.M 1.5. Finally, based on these attempts, the n-c-AlGaAs/ p-c-GaAs structure is suggested as promising solar cell applications and the actual model is intended to be extended to multilayer solar cells.
关键词： Solar cell,E?ciency,Thickness,Sun concentrations,Doping concentration,Recombination velocities
更新于2025-09-12 10:27:22
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A theoretical investigation of erbium‐doped fiber laser as a function of ion‐clustering, temperature, pumping wavelength, and configuration
摘要： The lasing performance of an erbium-doped fiber laser (EDFL) is affected by several factors such as doping concentrations, erbium-ion clustering, pumping wavelength, pumping configuration, and temperature. In this article, the performance of an EDFL has been investigated as a function of erbium-ion clustering, pumping wavelength, pumping configuration, and temperature. In our investigation, we have found that power degradation, which happens due to ion-clustering, at around 1530 nm is less affected for 980 nm pumping than for 1480 nm pumping. Moreover, a wider tuning range is achieved for 980 nm pumping than 1480 nm pumping. Our simulation results also show that the forward pumping configuration is suitable for a wider tuning range. To our best knowledge, pumping wavelength and configuration effects on an EDFL performance have not been investigated yet. We have also investigated the temperature effects on an EDFL performance and found little influence on lasing performance, at least within 30°C to 80°C.
关键词： doping concentration,pumping wavelength,temperature,pumping configuration,erbium-ion clustering,erbium-doped fiber laser (EDFL)
更新于2025-09-11 14:15:04
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An effective thermally activated delayed fluorescence host material for highly efficient blue phosphorescent organic light-emitting diodes with low doping concentration
摘要： A thermally activated delayed fluorescence (TADF) material BCz-2SO has been designed and synthesized as host for blue phosphorescent organic light-emitting diodes (OLEDs). Photophysical studies and theoretical calculations show that the molecule has a small singlet-triplet energy gap (ΔEST) of 0.345 eV, which is beneficial to the reverse energy transferring between the singlet and triplet state. Thanks to the TADF property, the triplet energy can be transmitted to the singlet state through reverse intersystem crossing (RISC), and then transmitted to the guest through the Fo?rster energy transfer (FET) to achieve 100% utilization of energy. Thus, the triplet–triplet annihilation (TTA) of the blue phosphor can be avoided by the extremely low doping concentration of 1%. By using BCz-2SO as the host of FIrpic, the solution-processed blue phosphorescent device achieves the maximum current efficiency (CE), power efficiency (PE), external quantum efficiency (EQE) and highest brightness of 16.38 cd A-1, 9.04 lm W-1, 7.8% and 16537 cd m-2, respectively. It demonstrates that one can employ the solution-processed method to prepare the high performance phosphorescent OLEDs using the TADF host material we have developed.
关键词： TADF,blue emission,organic light-emitting diodes,low doping concentration,solution-process
更新于2025-09-11 14:15:04