Carrier Concentration Mobility Research Articles

Highly solar transparent and low-emissivity glass based on hydrogen-doped indium oxide

Windows contribute significantly to heat loss in buildings, making them a critical focus for energy-saving measures aimed at reducing the substantial energy consumption in the building sector. This study explores ’high-transmittance, low-emissivity’ windows, which is beneficial for energy conservation in cold regions. Numerical calculations and experimental validation were used to develop a novel material optimization strategy utilizing hydrogen-doped indium oxide (IHO) films. The optimized IHO films exhibit high mobility (100 cm2/V·s) and low carrier concentration (2.2 × 1020 cm−3), providing superior performance compared to traditional transparent conductive oxide (TCO) films. The developed low-emissivity (low-e) passive insulation composite film demonstrates enhanced spectral characteristics. It achieves a solar transmittance of 0.836 and a mid-infrared (MIR) emissivity as low as 0.117, surpassing the performance of commercial low-e glass. This approach not only addresses the spectral limitations, such as poor NIR transmittance and high emissivity, of traditional low-e coatings but also establishes a universally applicable methodology for material selection and optimization.

2D g-C3N5 p-Doping of Donor Material for High-Efficiency Organic Solar Cells.

Molecular doping of organic semiconductor is a great strategy for significantly regulating the electronic band structure of organic semiconductor while increasing charge mobility and carrier concentration. Here, a facile strategy is presented by introducing 2D g-C3N5 as a p-dopant into PM6, improving the charge mobility and hole carrier concentration of PM6. Moreover, the electron transfer between PM6 and g-C3N5 can effectively downshift the Fermi energy level and highest occupied molecular orbital (HOMO) energy level of PM6, which leads to the increase the built-in electric field of organic solar cells (OSCs). The addition of g-C3N5 also effectively enhances the crystallization of active layer, thereby improving the stability of OSCs. As a result, a champion bulk-heterojunction (BHJ) and layer-by-layer (LbL) structure OSCs are successfully achieved featuring a high-power conversion efficiency of 18.10%/18.25%, simultaneously having excellent device stability. This work shows that introducing a low concentration dopant into organic donor is an effective method for improving the electrical performance of organic donor and the efficiency of OSCs.

Upper limit of mobility and concentration of charge carriers in fluoride superionic conductors with fluorite and tysonite structures

Within the framework of a crystal-physical model, the maximum values of mobility and concentration of charge carriers in fluoride superionic conductors belonging to the structural types of fluorite (CaF2, SrF2, BaF2, PbF2) and tysonite (LaF3) were calculated. It has been shown that the upper limit of ionic conductivity, mobility and charge carrier concentration in the crystalline state of fluoride superionics is 4 ± 1 S/cm, (5 ± 1) × 10–3 cm2/(сВ) и (5 ± 2) × 1021 cm–3 (10 ± 4% of the total fluoride ions), respectively.

Fundamental Understanding of Halide Solid Electrolytes for All-Solid-State Batteries

Due to their superior oxidative stability, high ionic conductivity and excellent chemical compatibility with uncoated 4 V-class cathode active materials, halide compounds, particularly those with a general formula of Li3MCl6 (M = Sc, Zr, In, Y, Er, and Yb etc.), have attracted much attention as solid electrolytes (SEs) for all-solid-state batteries (ASSBs).1,2 While a great deal of effort has been devoted to the discovery of new halide SEs,3–5 fundamental understanding of their properties, such as the mechanism of ionic conductivity, chemical stability, and the interfacial reactivities at the cathode and the anode are still lacking. Here we use Li3YCl6 (LYC) as an example to investigate the key parameters that impact their performances in ASSBs. Hopping frequency analysis is used to understand how synthesis methods and chemical compositions affect mobile carrier concentration and ionic conductivity in the Li–Y–Cl series.6 Synchrotron X-ray absorption (XAS) and diffraction (XRD) are used to investigate electrochemical and interfacial chemistry of LYC in full ASSB cells with an uncoated nickel-rich cathode, a Li metal anode or a lithium-metal alloy anode. Our strategies in developing halide SEs for higher capacity and high energy density ASSBs will be presented.

Assessment of superconducting and structural stability of advanced Y-123 and Y-358 ceramics with Tb/Y substitution in main matrices

In this study, the performances of Y1-x(Tb)xBa2Cu3O7-δ (Y-123) and Y3-x(Tb)xBa5Cu8O18-δ (Y-358) advanced ceramics prepared by sol-gel preparation route are investigated by the advanced characterization methods including X-ray diffraction (XRD), temperature dependent resistivity (ρ-T), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and energy distribution spectroscopy (EDS) measurements and theoretical approaches. The EDS results illustrated that the Tb impurities were replaced successfully by the yttrium sites in the YBa2Cu3O7-y main matrix. Similarly, it was noted that the presence of excess impurities in the crystal structure led to the oxygenation problems. Electrical properties were determined by temperature dependent resistivity (ρ-T) measurements. ρ-T results indicated that Tb doping reduced the critical transition temperature (Tc) values for the transition to superconductivity for all samples in two YBCO phases. Although it appears to have negative effects of Tb ions on the number of mobile charge carrier concentrations in the σ antibonding in-plane Cu-O bonds, bipolaron formations in the polarizable lattices, oxidation states, and amplitude of the pair wave function of both phases, the other valuable properties (morphology, crystallinity quality, interaction between adjacent layers, critical current density, and flux pinning ability) were noted to improve remarkably in the case of the optimum amount in the Y-123 superconducting phase. In this context, the Y-358 superconducting phase was harshly affected by the substitution due to the change of the ortorombicity, localization problem, impurity phases, structure stabilization, crystal structure quality, crystallization system, homogeneities of oxidation states, oxygen ordering degree, and impurity scatterings. Besides, the analysis of the fluctuation induced conductivity indicated that the Y-123 ceramics with longer c-axis coherence length and less anisotropic nature exhibited well superconducting properties. Additionally, the doping ratio of x=0.01 led to the formation and distribution of more nucleation centers for the thermal fluxon motions of 2D pancake vortices. Similarly, the optimum Tb doped Y-123 system exhibited much durable to applied field strengths due to the best interaction quality between grains. Accordingly, this study recommended that the Y1-x(Tb)xBa2Cu3O7-δ advanced ceramic structure with new functionalities can find much more application areas in innovative, heavy-industrial technologies, and advanced engineering-related sectors.

Wafer level quasi-van der Waals epitaxy of AlGaN/GaN heterojunctions on sp2-bonded BN controlled by AlN nucleation layer

Two dimensional materials, such as sp2-bonded boron nitride (BN) and graphene, have been proven to be excellent templates for the growth and fabrication of independent group III-nitride materials. Herein, wafer level sp2-bonded BN film was successfully grown as a release layer on two-inch sapphire substrate using MOCVD. The different nucleation mechanisms of gallium nitride (GaN) and aluminum nitride (AlN) grown on the BN surface were investigated. We discovered that AlN has a higher nucleation island density compared to GaN on the surface of BN which facilitates better merging of the GaN epitaxial layer. In addition, the quality of the GaN epitaxial layer was optimized by adjusting the growth temperature of AlN. A complete AlGaN/GaN heterojunction structure was subsequently grown on the best quality of GaN, and its average mobility and interlayer carrier concentration was about 1600 cm2 V−1 s−1 and 1 × 1013 cm−2. Finally, the AlGaN/GaN heterojunction was easily transferred from the substrate using tape, which proved the good 2D characteristics of sp2-bonded BN and can undergo non-destructive van der Waals transfer for the upper layer device.

Cobalt ferrite induced enhancement in the thermoelectric properties of zinc oxide composites

Thermoelectric (TE) material devices can be treated as an initiative to reduce global warming by scavenging waste heat and recycling it into useful electrical energy. In dual-phase materials, the energy filtering mechanism serves a significant role to enhance power factor by controlled electrical conductivity and Seebeck coefficient in connection with carrier concentration and carrier mobility. Here we performed the preparation of Cobalt Ferrite (CF) using mechanical alloying and the cf@zno composites via solid state reaction technique by varying stoichiometric weight between CF and ZnO. The magnetic, electric, and optical properties of the samples exposed the influence of CF on the TE properties of ZnO matrix. The cf7.5wt%@zno sample shows greater carrier mobility and moderate carrier concentration results the improved electrical conductivity value 4235 Sm−1 and hence achieved highest power factor 439 μWm−1K−2.

High-performance p-type V2O3 films by spray pyrolysis for transparent conducting oxide applications.

High-quality epitaxial p-type V2O3 thin films have been synthesized by spray pyrolysis. The films exhibited excellent electrical performance, with measurable mobility and high carrier concentration. The conductivity of the films varied between 115 and 1079 Scm-1 while the optical transparency of the films ranged from 32 to 65% in the visible region. The observed limitations in thinner films' mobility were attributed to the nanosized granular structure and the presence of two preferred growth orientations. The 60nm thick V2O3 film demonstrated a highly competitive transparency-conductivity figure of merit compared to the state-of-the-art.

THE OPTIMIZATION OF P3HT:PCBM THIN FILM THICKNESS FOR ORGANIC SOLAR CELLS

This study presents the complex relationship between film thickness and the properties of P3HT:PCBM thin films, looking at how different thicknesses affected their structural and optical properties. Poly(3, hexylthiophene) (P3HT) and poly(3, hexylthiophene) (PCMB) were blended in a 0.6:1 ratio and deposited using spin coating techniques. The research involve investigating the resulting changes in surface topography, optical properties, and electrical behaviour by systematically adjusting the film thickness through multiple coating repetitions ranging from one to three repetitions. Profilometric analysis revealed a direct relationship between film thickness and surface roughness, highlighting the importance of thickness in interfacial interactions within solar cells. Optical studies revealed fascinating trends in absorbance, transmittance, absorption coefficient, and extinction coefficient, highlighting the films' behaviour at various wavelengths. Surprisingly, regardless of thickness, the optical band gap remained constant, providing valuable insights for optimizing photon energy conversion. Measurements of the Hall effect revealed the effect of thickness on carrier mobility, concentration, conductivity, resistivity, and Hall voltage. Thinner films had higher mobility but lower carrier concentration, revealing a delicate balance critical for optimizing charge transport. The comprehensive analysis of the study sheds light on the complex interplay between film thickness and various properties, providing useful guidance for designing efficient P3HT:PCBM organic solar cells. This study's findings highlight the importance of precise control over film dimensions in improving the performance and efficiency of organic photovoltaic devices. This investigation paves the way for tailored approaches in the fabrication of next-generation organic solar cells, pushing the limits of renewable energy technology.

Al 0.3 Ga 0.7 N/GaN HEMT Yapısı için QMSA Metodu Uygulanması

In this study, Al 0.3 Ga 0.7 N/GaN high electron mobility transistor (HEMT) structure is grown on a sapphire (Al2O3) substrate by using metal-organic vapor phase epitaxy (MOVPE), and its electron transport and magnetic transport properties are investigated. Resistivity is measured in the 20-350 K temperature range. Hall mobility and Hall carrier concentration are measured in the 0-1.5 T magnetic field range and the same temperature range. Magnetic transport properties are analyzed using quantitative mobility spectrum analysis (QMSA). 2DEG and 3DEG transport mechanisms are separated by using QMSA results.

Titanium dioxide (TiO2) and gel-polymer solar cells

This research focuses on the study of semiconductor-based solar cells utilizing titanium dioxide (TiO2) and gel-polymer electrolytes. The technology for preparing the electrolytes used in these solar cells has been developed, encompassing both liquid and gel polymer electrolyte compositions. The electrochemical impedance method is employed to determine important parameters such as diffusion coefficient, mobility, and charge carrier concentration in both liquid and gel-polymer electrolytes. Experimental results are compared with theoretical calculations utilizing the electrochemical impedance spectroscopy graph. Moreover, the photon-to-current conversion efficiency of the semiconductor-based solar cells is determined using the Incident Photon to Current Conversion Efficiency (IPCE) method, covering a wavelength range of 300 nm to 900 nm.

Electrical Properties of GaN Cap Layer for AlGaN/GaN HEMT

Metal organic chemical vapor deposition (MOCVD) was used to grow AlGaN/GaN HEMT on a sapphire substrate with a 3.0 nm GaN cap and a sample without a GaN cap. High resolution X-ray diffraction (HRXRD) was utilized to investigate the structural characteristics of the materials. The relationship between the electrical properties and two-dimensional electron gas (2DEG) I-V and Hall Effect measurement. The I-V measurement was used to investigate the resistance properties of AlGaN/GaN heterostructures. Hall Effect measurement was used to quantify electron mobility and sheet carrier concentration in both samples. The sample with a 3.0 nm GaN cap exhibited excellent electrical properties with 436.8 Ω/sq sheet resistivity and possessed a high value of sheet carrier concentration 3.46E+14 per cm2.

Hopping Rate and Migration Entropy as the Origin of Superionic Conduction within Solid-State Electrolytes.

Inorganic solid-state electrolytes (SSEs) have gained significant attention for their potential use in high-energy solid-state batteries. However, there is a lack of understanding of the underlying mechanisms of fast ion conduction in SSEs. Here, we clarify the critical parameters that influence ion conductivity in SSEs through a combined analysis approach that examines several representative SSEs (Li3YCl6, Li3HoCl6, and Li6PS5Cl), which are further verified in the xLiCl-InCl3 system. The scaling analysis on conductivity spectra allowed the decoupled influences of mobile carrier concentration and hopping rate on ionic conductivity. Although the carrier concentration varied with temperature, the change alone cannot lead to the several orders of magnitude difference in conductivity. Instead, the hopping rate and the ionic conductivity present the same trend with the temperature change. Migration entropy, which arises from lattice vibrations of the jumping atoms from the initial sites to the saddle sites, is also proven to play a significant role in fast Li+ migration. The findings suggest that the multiple dependent variables such as the Li+ hopping frequency and migration energy are also responsible for the ionic conduction behavior within SSEs.

Mechanochemical Synthesis and Fluoride Ion Conductivity Studies in SrSnF4 Polymorphs

Investigations on SnF2-based solid electrolytes are gaining significant scientific attention because of their promising applications as solid electrolytes for all-solid-state fluoride ion batteries (FIBs) operating at room temperature. FIBs are potential alternatives for expensive Li-ion batteries with toxic and flammable liquid electrolytes. SrSnF4 belongs to the MSnF4 (M: Pb, Ba, and Sr)-type materials exhibiting a layered structure. Here, we present the structural and transport characteristics of two polymorphs of SrSnF4 using X-ray diffraction and impedance spectroscopy techniques. SrSnF4 crystallizing in a cubic fluorite structure is obtained just by mechanical milling the powder samples of SrF2 and SnF2 taken in a 1:1 ratio for 10 h, whereas annealing the milled powder at 623 K in the N2 atmosphere transforms SrSnF4 from its cubic phase to the stable tetragonal structure. The structural details of both the cubic and tetragonal SrSnF4 have been obtained by performing the Rietveld refinement. The resultant phase change after soft annealing enhances the room-temperature conductivity value from 2.05 × 10–6 S/cm for the cubic phase to 1.16 × 10–5 S/cm for the tetragonal phase. The transport number measurement by the dc polarization technique with the cell of configuration Ag/SrSnF4/Ag reveals that the conductivity is due to the ions. The frequency response of conductivity data is analyzed using the Almond–West formalism to find their hopping frequency and mobile carrier concentration factor at different temperatures. The scaling of the frequency-dependent conductivity spectra shows that the relaxation behavior of the mobile ions is temperature independent.

Silicon-doped β-Ga2O3 films grown at 1 µm/h by suboxide molecular-beam epitaxy

We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate of ∼1 µm/h with control of the silicon doping concentration from 5 × 1016 to 1019 cm−3. In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga2O, i.e., gallium suboxide, is supplied. Directly supplying Ga2O to the growth surface bypasses the rate-limiting first step of the two-step reaction mechanism involved in the growth of β-Ga2O3 by conventional MBE. As a result, a growth rate of ∼1 µm/h is readily achieved at a relatively low growth temperature (Tsub ≈ 525 °C), resulting in films with high structural perfection and smooth surfaces (rms roughness of <2 nm on ∼1 µm thick films). Silicon-containing oxide sources (SiO and SiO2) producing an SiO suboxide molecular beam are used to dope the β-Ga2O3 layers. Temperature-dependent Hall effect measurements on a 1 µm thick film with a mobile carrier concentration of 2.7 × 1017 cm−3 reveal a room-temperature mobility of 124 cm2 V−1 s−1 that increases to 627 cm2 V−1 s−1 at 76 K; the silicon dopants are found to exhibit an activation energy of 27 meV. We also demonstrate working metal–semiconductor field-effect transistors made from these silicon-doped β-Ga2O3 films grown by S-MBE at growth rates of ∼1 µm/h.

Characterization of Bipolar Transport in Hf(Te1−xSex)2 Thermoelectric Alloys

Control of bipolar conduction is essential to improve the high-temperature thermoelectric performance of materials for power generation applications. Recently, Hf(Te1−xSex)2 alloys have gained much attention due to their potential use in thermoelectric power generation. Increasing the Se alloying content significantly increases the band gap while decreasing its carrier concentration. These two factors affect bipolar conduction substantially. In addition, the weighted mobility ratio is estimated from the experimental electronic transport properties of Hf(Te1−xSex)2 alloys (x = 0.0, 0.025, 0.25, 0.5, 1.0) by using the Two-Band model. From the bipolar thermal conductivity also calculated using the Two-Band model, we find that it peaks near x = 0.5. The initial bipolar conductivity increase of x < 0.5 is mostly due to the decrease in the weighted mobility ratio and carrier concentration with increasing x. For x > 0.5, the drop in the bipolar conductivity can be understood with significant band gap enlargement.

Selective Release of Excitatory‐Inhibitory Neurotransmitters Emulated by Unipolar Synaptic Transistors via Gate Voltage Amplitude Modulation

AbstractOrganic field‐effect transistor (OFET) memory devices are benefiting from their independent gate modulation advantages for hardware implementation of synaptic functionalities. However, the imitation of selective release of excitatory–inhibitory neurotransmitters in a unipolar synaptic OFET is challenging due to the unbalanced mobile carrier concentration. Here, a p‐type synaptic OFET memory with CsPbBr3 quantum dots (QDs) as nano‐floating gates (NFGs) is developed, which can emulate both the excitatory–inhibitory responses of the biological synapse and their reconfigurable nature. By controlling the offset difference between stimulus voltage and reading voltage, the concomitant and independently expressed excitatory and inhibitory responses are successfully implemented in a negative gate modulation manner, but without introducing an ambipolar semiconductor or additional optical terminal. This reconfigurable modulation is ascribed to the dynamic competition between external electric field and built‐in electric field assisted by charge trapping in shallow traps. The proposed gate voltage‐offset method can be generally adapted to other unipolar synaptic OFETs. These results provide insight into OFET memory devices for building neuromorphic hardware elements with tailorable synaptic plasticity.

Structural role of double layer amphoteric oxides forms on electrical conductivity: PbO/zinc oxide semiconductor

We have investigated the electrical properties of PbO/Zinc Oxide double-layer semiconductor (DLS) diodes such as series resistance (), ideality factor (), and barrier height (). The samples were manufactured by using an evaporation technique at room temperature. To obtain their main electrical parameters, current-voltage (I–V) measurements have been performed in the dark and at room temperature. In the study, we examined two diodes to evaluate the electrical characteristics of PbO/Zinc Oxide double-layer semiconductor (DLS) diodes using the thermionic emission (TE) theory, Norde’s method, and Cheung’s functions. While n, and values of Diode 1 were found to be 4.02, 0.739 eV, and 1.506. 10−8 A respectively, the same values of Diode 2 were calculated as 4.14, 0.724 eV, and 2.65.10−8 A, respectively, by using the TE method. The values of n, and were also calculated using the Cheung’s method, and they were found to be 10.048, 0.549 eV, and 4.058 respectively, for Diode 1, while these values were calculated as 8.116, 0.659 eV, and 7.799 respectively, for Diode 2. and values are also ascertained as for Diode 1 and for Diode 2, for Diode 1 and for Diode 2 using Norde Method, respectively. The forward bias I–V characteristics were used to obtain the energy distribution of the interface state density considering the effective barrier height’s bias dependence. The change observed in the interface state density’s magnitude ranged between and The evaluated series resistance indicates the product of mobility and free carrier concentration, ideality factor is a measure of how closely the diode follows the ideal diode equation, and barrier height also depends on the concentration of carriers in PbO/Zinc Oxide double-layer semiconductors.

Influence of Fe/Ca substitute on fundamental properties of Bi1.8Pb0.35Sr1.9Ca2.2−xFexCu3Oy materials

In the present study, the role of Fe/Ca partial replacement in Bi1.8Pb0.35Sr1.9Ca2.2−xFexCu3Oy (Bi-2223) superconducting material on the crystallinity, electrical, structural morphology and superconducting properties is studied by way of the electrical resistivity (ρ-T), powder X-ray diffraction (XRD), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) measurements. According to the experimental results, the Fe additives are effectively replaced by the Ca sites in the bulk Bi-2223 superconducting system, verified by evidenced by the ρ-T and EDX results. Further, the SEM images show that the crystallinity quality and surface morphology view undermine considerably with the enhancement in the Fe/Ca partial substitution level in the Bi-2223 system because of nonuniform surface appearance with new induced permeant structural deformations, impurity residues, misorientations of grains and systematic problems in the grain boundary couplings in the superconducting system. Additionally, the disappearance or appearance of some diffraction peaks in the XRD pattern as well as the decrease in the c-axis length and increase a-axis length provides the deviation of the Bi-2223 materials from stabilization in the system because of the degradation in the crystal structure quality. Besides, the dc electrical results represent that the electrical and fundamental superconducting characteristics decrease with the increase of Fe/Ca replacement owing to the increment of inhomogeneities in the oxidation state, structural problems and mobile hole carrier concentration in the bulk Bi-2223 materials.

Effect of Ni and Al doping on structural, optical, and CO2 gas sensing properties of 1D ZnO nanorods produced by hydrothermal method.

In the present study, the one-dimensional ZnO nanorod structures are produced within the different nickel and aluminum molecular weight ratios of 0-7% using the hydrothermal method. It is found that the aluminum (Al) and nickel (Ni) impurities with different ionic radius, chemical valence, and electron configurations of outer shell cause to vary the fundamental characteristic features including the crystallinity quality, crystallite size, surface morphology, nanorod diameter, optical absorbance, energy band gap, resistance, gas response, and gas sensing properties. The structural analyses performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the samples are found to crystallize in the hexagonal wurtzite structure. The presence of optimum nickel and aluminum in the crystal system improves considerably the crystallinity quality and surface morphology. Additionally, the combination of electron dispersive X-ray (EDX) and XRD results declare that the Ni and Al impurities incorporate successfully into the ZnO crystal structure. Moreover, the diameters of nanorod structures in 1D orientation are determined to be 80 nm or below. The hexagonal wurtzite-type ZnO nanorod structure prepared by 5% Ni has more space between the nanorods and thus presents higher response to the CO2 detection. Further, the optical absorbance spectra display that the band gap value is observed to decrease regularly with the increment in the doping level as a result of band shrinkage effect depending on the enhancement of mobile hole carrier concentrations in the crystal structure. In other words, the doping mechanism leads to vary the homogeneities in the interfacial charges, nanorod diameters, ZnO oxide layer composition and thickness. The last test conducted in this study is responsible for the determination of CO2 gas sensing levels. The obtained gas sensing results are further compared with each other and literature findings. It is observed that 5% Ni-doped sample provides more successful results than other samples in the sensing CO2 gas at the different concentrations. All in all, the paper establishing a strong methodology between doping mechanism and change in the fundamental characteristic features of hexagonal wurtzite-type ZnO with the aid of advanced microscopy techniques will become pioneering research to answer key questions in materials sciences and electronic research.