Impurity Trapping Research Articles

Asymmetrical impurity effect of C70:C60 mixture in thick small molecule organic photovoltaic cells

Fullerenes, especially C70 and C60, and their derivatives are popular acceptor materials for many organic semiconductor devices, including organic photovoltaic cells. One of the main impurities in C70 is C60, and intentional mixture of C60 and C70, or their derivatives, which have been utilized for maximizing the performance of organic photovoltaic cells or perovskite solar cells. However, the influence of impurities in C70 on the device characteristics has not been fully clarified when incorporating C70 into organic devices. To further clarify the relationship between the fullerene mixture and impurities, the effect of impurities in fullerenes on thick photovoltaic cells was evaluated, and a strange asymmetrical impurity effect of the C60:C70 mixture was demonstrated by using C70 with various purities as an acceptor material and zinc phthalocyanine (ZnPc) as a donor material. It was found that C60, C78, and C84 impurities in C70 caused carrier recombination during electron transport, but the same effect of the C70 impurity in C60 was much smaller. Additionally, the impurity effect of higher fullerenes on C70 was clearly larger than that of C60. The effect of higher fullerene impurities can be explained by electron trapping due to their deep lowest unoccupied molecular orbital (LUMO) levels. For the small difference of LUMO energy between C70 and C60, however, it is suggested that the shallow trapping of C70 impurities does not largely inhibit the transport of photocarriers by C60, while the low energy barrier of C60 impurities largely inhibits the transport of photocarriers by C70. For clear comparison, the photoelectrical conversion layers were crystallized using co-evaporant induced crystallization. An effective purification method for C70 using sublimation purification, which depends on the C70 concentration in the sublimation source, is also reported.

Effects of Lu on the α-Al2O3/β-NiAl interface adhesion from first-principles calculations

The effects of the reactive element lutetium (Lu) addition on the α-Al2O3(0001)/β-NiAl(110) interface adhesion is investigated from first-principles calculations. Our results show that Lu can improve the α-Al2O3/NiAl interface adhesion by three mechanisms: (i) trapping impurity sulfur (S) in the NiAl bulk by forming Lu-S bonds thereby reducing detrimental S segregation to the Al2O3/NiAl interface, (ii) promoting Lu segregation to the α-Al2O3/NiAl interface, thus blocking the segregation of S toward the oxide/alloy interface, (iii) enhancing the α-Al2O3/NiAl interfacial bonding strength by forming Lu-O and Lu-Ni bonds across the interface. These results rationalize the reactive element effect on the high-temperature oxidation resistance of alumina-forming alloys.

Switching and photosensitive analysis of dopingless tunnel field effect transistor based on cladding layer concept

— In this paper, the switching and photo sensing analysis of cladding layer based dopingless Tunnel FET (CDL-TFET) has been examined under visible range of spectrum. Initially, the impact of cladding layer in DL-TFET on electrical parameter is observed by varying the source material and thickness of source region. Furthermore, CDL-TFET is used for photo sensing application under the light state at various wavelength of light incident. The various optical figure of merits (FoMs) like spectral sensitivity (Sn), Signal to noise ratio (SNR), Responsivity (R), and quantum efficiency (η) is extracted to realize the behavior of photosensor. The maximum value of Sn is 48, R of 0.74 (A/Watt), SNR of 68.8 dB, and η of 3 are obtained at λ = 300 nm. Further, impurity trap charge effects are also observed at the interface and bulk of TFET. Finally, a comparison table has been presented to signify the importance of cladding layer based DL-TFET photo sensor with existing literature.

Electron-hole trapping centers in Na2SO4 with a transition metal impurity Mn

The Na 2 SO 4 samples were obtained by slow evaporation method. The mechanisms of the formation of electron and hole trapping centers are investigated by spectroscopic methods. Intrinsic recombination emission of 2.9–3.1 eV and impurity emission of 1.85 eV are excited at 4.0–4.5 eV. Intrinsic SO 3− 4 −SO − 4 and impurity Mn + − SO − 4 trapping centers were revealed. The local levels corresponding between the electron and hole trapping center are 4.0–4.5 eV. The decay of intrinsic and impurity trapping centers was recorded at temperatures of 130–150 K and 280–350 K.

Permeability coefficient of pervious cement mortar measured by the constant head and falling head methods

The modified previous concrete and cement mortar, known as previous cement mortar (PCM), is designed with a specific composition to create pores. The coarse aggregate is removed to form smaller pore sizes. PCM acts as a water filter, needing higher permeability than cement mortar but less than previous concrete. Its pores drain water while trapping impurities. This study compares the effects of sand-to-cement ratio (S/C), specimen thickness, and age on permeability and porosity. It also contrasts PCM's permeability coefficient determined by constant head and falling head methods. Numerous studies compare permeability coefficients in previous concrete using these methods, but not for finer aggregate cement-based composite materials like previous cement mortar. PCM uses fine aggregate (0.6-0.85 mm) at 3, 5, and 10 cm thickness with S/C ratios of 4 and 5. Findings show that S/C 5 specimens have significantly higher porosity than S/C 4. The S/C ratios notably impact permeability; the higher ratio means the higher permeability. Permeability coefficients for S/C 4 ranging from 0.006-0.075 cm/s, while S/C 5 ranging from 0.010 to 0.147 cm/s. The relationship between the permeability coefficient between the constant head and falling head methods at the age of 90 days specimen are Kc = 1.0516 Kf (S/C 4.2) and Kc = 0.9325 Kf (S/C 5.2). According to these findings, finer aggregates result in a significantly smaller permeability, to the extent that the constant head method is more reliable compared to the falling head method.

Activated Carbon Derived from Peltophorum pterocarpum (Copper Pod) Seeds and Phoenix dactylifera (Date Plam) Seeds in Batch Comparative Adsorption Studies of Fluoride

A synthesis of two forms of activated carbons is included in this paper. Because of its capacity to remove contaminants from both air and water, activated carbon (AC) is commonly employed for purification. Its porous structure allows it to trap impurities, and it is frequently suggested for a variety of water and wastewater treatment applications. However, due to the high expense of filing an AC application, the number of applications that can be filed is limited. AC was made using locally accessible Peltophorum pterocarpum (Copper Pod) and Phoenix dactylifera (Date Plam) seeds in this study. Fluoride adsorption on physical activated carbon from a synthetic sample made from Peltophorum pterocarpum (Copper Pod) and Phoenix dactylife. To remove fluorine from the body physically activated carbon, adsorption in batches methods were completed in order to find the best time, dose, pH sorption kinetics, and sorption equilibrium. The ideal contact duration, dosage of adsorbent and carbon pH were found to be 30 minutes, 140 mg, and 8.00, and 50 minutes, 225 mg, and 9.00, with fluoride removal efficiency of 77.5 percent, 79.33 percent, 82.6 percent, and 72.63 percent, 75.8%, 76.5 percent, respectively. Changes in process factors such as adsorption time and dosage were recycled to inspect adsorption kinetics and sorption isotherm models. The isotherms of Langmuir, Freundlich, and Temkin are three scientists investigated using This experimental data has been determined to be accurate.

Breathing dynamics of the few-body Bose polaron in a species-selective harmonic trap

We perform an extensive numerical study on the breathing dynamics of a few-body Bose polaron setup in a one-dimensional species-selective harmonic trap. The dynamics is triggered by a quench of the impurity trap. The excitation of the background majority atoms is mediated via the majority-impurity interaction. The breathing spectrum is obtained for different numbers of majority particles, several values of the majority-component interaction strengths and trap ratios. It is further compared to the breathing spectrum of a particle-balanced few-body Bose-Bose mixture. In particular, for equal post-quench traps the employed protocol allows to couple states of different center-of-mass parity in contrast to species-symmetric trap quenches. Among the participating eigenstates we identify one having odd center-of-mass parity and even global parity. The breathing frequency induced by this state is a monotonically decreasing function of the coupling parameter. Importantly, in order to be observable it requires the entanglement between the species to be taken into account. We demonstrate this by comparing the numerically exact results obtained by means of the Multi-Layer Multi-Configuration Time-Dependent Hartree Method for Mixtures to the ones of a species mean-field ansatz. The entanglement-sensitive breathing frequency persists also for unequal post-quench traps where the center-of-mass cannot be decoupled. Finally, we analyze the impact of parity symmetry on the breathing dynamics by initializing a state of odd global parity. We evidence a striking resemblance to the ground state breathing dynamics.

Spin Polarization-Assisted Dopant Segregation at a Coherent Phase Boundary.

Coherent phase boundaries are widely expected as segregation-free boundaries due to their low interfacial energies and lack of trapping sites for impurities. Here, we report an equilibrium segregation of W atoms at fully coherent terraces of a Fe3O4 (111)/Fe2O3 (0001) phase boundary that was never expected previously. Through comparison of pristine and W-doped Fe3O4/Fe2O3 phase boundaries, it is revealed that the spin polarization of O atoms at the interface plays an important role in the periodic segregation of W atoms. Unusual spin-polarized O atoms with large magnetic moments are periodically arranged in the interfacial O plane of the pristine phase boundary. After doping of W at this boundary, W atoms will selectively substitute the Fe atoms of Fe2O3 that directly bond with three spin-polarized O atoms, thereby resulting in the complete neutralization of the magnetic moments of the spin-polarized O atoms. These findings reveal that coherent phase boundaries are able to trap impurities and local spin polarization is one of the driving forces for dopant segregation, suggesting that elemental doping is an efficient way for tailoring the physical properties of boundaries in magnetic materials and devices.

Effect of purity on the vacancy defects induced in self–irradiated tungsten: A combination of PAS and TEM

Vacancy defects in tungsten induced by self-ion irradiation were characterized by positron annihilation spectroscopy (PAS) and transmission electron microscopy (TEM). Taking advantage of their complementarity, defects ranging from single vacancies up to vacancy clusters were detected, and the effects of sample purity (99.95 wt.% and 99.9999 wt.%) on their formation and evolution under low damage dose (0.01 to 0.02 dpa) irradiation with 20 and 1.2 MeV-W ions were studied at room temperature (RT), 500 and 700 °C respectively. When irradiation was performed at RT, PAS probed mainly single vacancies. At high irradiation temperatures, larger vacancy clusters were detected by both techniques. Both PAS and TEM revealed larger vacancy clusters in the purest samples after irradiation at 500 and 700 °C. A significant difference in the evolution of vacancy-type defects related to sample purity was observed. In view of the properties (migration, trapping) of some light-element impurities (LEs), present at high concentrations, determined by first-principles calculation, it is reasonable to assign the effect of purity during the irradiation response to the formation of vacancy-impurity complexes, which is critical for the understanding of the behavior of tungsten in the future fusion reactor.

A Novel Method of Purifying Metallurgical-Grade Silicon Using Mn as an Impurity Trapping Agent

A Novel Method of Purifying Metallurgical-Grade Silicon Using Mn as an Impurity Trapping Agent

Influence of Cu+ impurity on the efficiency of creation of electron-hole trapping centers in irradiated Na2SO4 − Cu crystals

The mechanisms of creation of impurity and intrinsic electron-hole trapping centers in Na2SO4 − Cu crystals have been investigated by spectroscopic methods. It is shown that impurity and intrinsic electron-hole trapping centers in the crystal lattice Na2SO4 − Cu are created in the same energy distances approximately 3.87-4.0 eV and 4.43-4.5 eV. During the annealing of electron-hole trapping centers, the energy of the recombination processes is transferred to impurities.

Investigation of Photoexcitation Energy Impact on Electron Mobility in Single Crystalline CdTe.

The exceptional electronic properties of cadmium telluride (CdTe) allow the material to be used in a wide range of high energy radiation detection applications. Understanding the mechanisms of local carrier scattering is of fundamental importance to understand the charge transport in the material. Here, we investigate the effect of photoexcitation on electron transport properties in chlorine doped single crystalline cadmium telluride (SC-CdTe:Cl). For this purpose time of flight measurements were performed on SC-CdTe:Cl in order to study the electron drift mobility in the low injection regime. Measurements were made at the temperature intervals of 80 to 300 K, for an applied electric field between 270 and 1600 V/cm and for wavelengths of 532, 355 and 213 nm. We have found that the electron drift mobility was affected by the excitation energy for temperatures below 200 K. In addition, the measurements revealed that it is possible to determine impurity and shallow trap concentration by this method. The method proves to be extremely sensitive in measuring very low impurity levels and in identifying dominant scattering mechanisms.

Quantum dynamics of impurities in a Bose–Einstein condensate

We study the quantum dynamics of the two impurities in a trapped quasi-one-dimensional Bose-Einstein condensate (BEC). We explore the effect of impurity-BEC and impurity-impurity interaction strengths on the dynamics of impurities inside the Bose-Einstein condensate. By studying the auto-correlation function of impurities and the BEC, we analyze and quantify the trapping of impurities inside the BEC. We find out that for the small value of inter-species coupling strength the BEC starts to oscillate inside the trap. For mild coupling strengths, attractive and repulsive impurities are captured after a few cycles of oscillation inside the BEC. In the strong interaction strength regime, the to-and-fro motion of impurities is suppressed quite fast. Our conclusion indicates that quench dynamics can be a tool for studying impurity BEC interactions or impurity-impurity interactions. Our analysis shows that the generation of phonon, shock waves, soliton trains, and self-trapping is strongly dependent on the impurity-BEC coupling coefficient.

On the exciton-assisted radiative recombination via impurity trap levels in AlGaN deep ultraviolet light-emitting diodes

For decades, problems of parasitic emissions have been ubiquitously encountered in nearly all deep ultraviolet light-emitting diodes (DUV-LEDs). In this work, 450 nm parasitic peaks in 275 nm AlGaN DUV-LEDs have been studied in details. Upon careful comparisons and analyses on the electroluminescence and photoluminescence spectra at various injection levels and different temperatures, we have discovered a mechanism of exciton-assisted radiative recombination, namely, the reinforcement on radiative recombination via other impurity-trap levels (ITLs) by excitons that are generated in the midst of the band gap. For DUV-LED samples under investigation herein, a system of radiative ITLs within the band gap cannot be neglected. It includes two types of impurities located at two different energy levels, 3.80 eV and 2.75 eV, respectively. The former, establishing a sub-band edge, which behaves like an energy entrance to this system, contains a series of hydrogen-like excitons at a temperature lower than 100 K, which behaves like an energy entrance to this system. On the one hand, these excitons absorb carriers from band-edge and reduce the band-edge recombination. On the other hand they transfer the energy to lower impurity levels, enhancing the radiative recombination and giving rise to the 450 nm parasitic peak.

Trapping of Impurity in a Dilute Solution: Phase-Field Simulation of Solidification

Trapping of Impurity in a Dilute Solution: Phase-Field Simulation of Solidification

Effects of IGZO film thickness on H2S gas sensing performance: Response, excessive recovery, low-frequency noise, and signal-to-noise ratio

In this work, we investigate the effects of IGZO film thickness on the H2S gas sensing performance, such as response, excess recovery, low-frequency noise (LFN), and signal-to-noise ratio (SNR) in the resistor- and FET-type gas sensors. A transition of the dominant sensing area from the surface to the bulk of the IGZO film is observed with increasing film thickness. Also, excessive recovery is observed and its detailed mechanism is analyzed for the first time. The resistor-type gas sensor with thicker IGZO film has a smaller 1/f noise due to the decreased trap density and impurity scattering, which guarantees the largest SNR and the lowest limit of detection (LOD). In the case of the FET-type gas sensor, the thicker film with high porosity allows H2S gas to diffuse more easily into the IGZO-O/N/O interface and increases the response. Also, the LFN characteristics of the FET-type gas sensor have no dependence on the IGZO film thickness. Thus, the SNR of the FET-type gas sensor is the largest when the IGZO film thickness is 60 nm.

Fabrication of Porous Lead Bromide Films by Introducing Indium Tribromide for Efficient Inorganic CsPbBr3 Perovskite Solar Cells.

In the process of preparing CsPbBr3 films by two-step or multi-step methods, due to the low solubility of CsBr in organic solvents, the prepared perovskite films often have a large number of holes, which is definitely not conducive to the performance of CsPbBr3 perovskite solar cells (PSCs). In response to this problem, this article proposed a method of introducing InBr3 into the PbBr2 precursor to prepare a porous PbBr2 film to increase the reaction efficiency between CsBr and PbBr2 and achieve the purpose of In (Ⅲ) incorporation, which not only optimized the morphology of the produced CsPbBr3 film but also enhanced the charge extraction and transport capabilities, which was ascribed to the reduction of the trap state density and impurity phases in the perovskite films, improving the performance of CsPbBr3 PSCs. At the optimal InBr3 concentration of 0.21 M, the InBr3:CsPbBr3 perovskite solar cell exhibited a power conversion efficiency of 6.48%, which was significantly higher than that of the pristine device.

ON current enhancement and variability suppression in tunnel FETs by the isoelectronic trap impurity of beryllium

We have experimentally demonstrated ON current enhancement and variability suppression of Si tunnel FETs (TFETs) by introducing an isoelectronic trap (IET) beryllium into the channel. In the previous studies, it was showed that the introduction of the Al-N IET impurity enables those requirements for Si-TFETs. In this study, we focused on Be as a new IET impurity and introduced the new IET into Si-TFETs. We found the optimum conditions for the formation of the Be-IET state in Si and demonstrated process integration of the Be-IET formation and TFET fabrication. The Be-introduced TFET exhibits five times enhancement of ON current; this enhancement ratio is larger than the case of the Al-N IET. Furthermore, significant suppression of the variability is achieved by Be-IET as well as the previous case of the Al-N IET. This better ON current improvement by Be-IET results from the energy level of Be deeper than that of Al-N IET, which plays a better role in enhancing the performance of Si-TFETs.

Ion-Exchange Separators Suppressing Self-Discharge in Polymeric Supercapacitors

Author(s): Wang, K; Yao, L; Jahon, M; Liu, J; Gonzalez, M; Liu, P; Leung, V; Zhang, X; Ng, TN | Abstract: Supercapacitors offer superior cycle life and high power densities, but as energy storage devices, they are limited by self-discharge processes manifested as large potential decay and leakage current, resulting in loss of stored energy and low charging efficiency. To minimize Faradaic side reactions, this Letter has incorporated a sulfonate ion-exchange resin in separators to trap impurities and thereby suppress self-discharge in supercapacitors with PEDOT as redox electrodes. The versatile separator design is generally applicable to organic and aqueous electrolytes and compatible with a pH range of 0-14, while maintaining the device capacitance and rate performance. Temperature-dependent characteristics were analyzed to identify that the reduction of impurity concentration and diffusion was key to improve potential retention. Compared to devices using commercially available separators, the device here exhibited a lower leakage current and better charging efficiency. It was demonstrated to work with radio frequency energy-harvesting circuits and showed the potential to serve as an energy reservoir for wireless electronic applications.

Effect of excitation wavelength and europium doping on the optical properties of nanoscale zinc oxide

The present study demonstrates a red light-emitting nano-phosphor material tailored by doping europium (Eu+3) ions in zinc oxide (ZnO), prepared using a solution based co-precipitation method. Instead of using acetates or nitrates based precursor for Eu+3 doping, here we directly used europium oxide (Eu2O3) as a precursor. The precursor showed a limited amount of solubility only up to 3% in an alcoholic solution. No phase change of any kind in x-ray diffraction (XRD) patterns indicates effective Eu+3 doping in ZnO. Also, the broadening of the XRD peaks confirms the reduction of size to the nanoscale. Further, the optical properties of pure ZnO and Eu+3-doped ZnO are elucidated using UV–Visible and photoluminescence (PL) spectroscopy. A redshift of 10 nm in the absorption edge from pure ZnO to 3% Eu+3-doped ZnO concentration is detected, indicating that Eu+3 ions occupy impurity trap levels below the conduction band. A regular increase in the excitation wavelength from 190 nm to 270 nm confirms that 226 nm excitation wavelength is the onset point for the emission from Eu+3 ions. The Eu+3-doped ZnO nanoparticles exhibit two emission peaks at 584 nm and 613 nm corresponding to 5D0→7F1 and 5D0→7F2 transition of Eu+3 ions at low excitation wavelengths of 254 nm and 270 nm. Out of these two peaks, 613 nm peak was the most intense suggesting that mostly 5D0→7F2 transitions are taking place. The intensity ratio of 5D0→7F2 / 5D0→7F1 for both excitation wavelengths of 254 nm and 270 nm is always greater than one confirms the efficient emission of red color from Eu+3 ions. In addition to that, the samples exhibit a high color purity value of 83.78 %, with CIE coordinates (0.60, 0.40) lying closer to the ideal red color CIE coordinates at an excitation wavelength of 254 nm.