Conduction Of Charge Carriers Research Articles

Charge Carrier Dynamics of Electrochemically Synthesized Poly (Aniline Co-Pyrrole) Nanospheres Based Sulfur Dioxide Chemiresistor

ABSTRACT Poly(aniline co – pyrrole) (PAP) nanospheres (diameter ~50 nm) have been synthesized by using cost-effective electrochemical oxidation of monomers, i.e., aniline, and pyrrole (1:1 ratio), and evaluated as sulfur dioxide chemiresistor. PAP chemiresistor exhibited an improved sensing response (6.1%) toward a low concentration of sulfur dioxide (5 parts per million) compared to its precursor-based chemiresistors at room temperature. It is attributed to the remarkable characteristics of PAP, such as higher surface-to-volume ratio, larger effective surface area, higher branching, and lower conductivity value. Furthermore, the cause of low conductivity was evaluated using low-temperature direct current charge transport studies. The dependence of activation energy on temperature discarded the probability of band conduction mechanism in the synthesized PAP nanospheres. PAP nanospheres were found to possess 3-Dimensional VRH conduction of charge carriers. The low conductivity of PAP nanospheres is further explained by evaluating Mott’s parameters, i.e., characteristic temperature, hopping radius, hopping energy, and density of states.

Dynamical response of localized electron hopping and dipole relaxation in Cu1 − x Zn x Fe2O4 magnetoceramics

We report a detailed study on the dynamical response of localized electron hopping and dipole relaxation in bulk polycrystals of Zn diluted Cuprospinel (Cu1 − x Zn x Fe2O4). The variations in the dielectric dispersion and ac-resistivity (ρ ac ) were analyzed over a wide temperature (77 K ≤T ≤ 823 K) and frequency (20 Hz ≤ f ≤ 20 MHz) window for a critical composition x c = 0.4. The variation of R (f, T) followed the Maxwell–Wagner type polarization mechanism in-line with the Koops phenomenological theory. Our analysis of ρ ac (T, f) provide strong evidence to the Mott’s variable range hopping of charge transport between the localized states at low temperatures, however, thermally-activated Arrhenius like behaviour was noticed at high temperatures with E A = 656 meV for x c = 0.4. Moreover, electric modulus spectroscopic studies (M *(f, T)) reveals two distinct types of relaxation phenomena: (i) the short-range oscillations of the charge carriers within the potential well of grains and (ii) the long-range movement of charge carriers across the grain boundaries. The depressed semi-circles of the Nyquist plots and lower values of non-exponential parameter extracted from M *(f, T) suggest the non-Debye type relaxation process present in the system with a widespread distribution of relaxation times. The frequency exponent (s(x, T)) study of Jonscher’s power law reveals that the ac-conductivity follows small-polaron tunnelling followed by the correlated-barrier-hopping mechanism for 0.1. However, for x ≥ x c reorientational hopping mechanism is predominant, except for 400 K, where thermally activated Arrhenius-type conduction of charge carriers is prevalent in this spinel system. Furthermore, the tetragonally (I41/amd) distorted systems (x ≤ 0.05) exhibit less activation energy (E A − VRH ) values as compared to those of cubic-spinel symmetry (Fd-3m) which saturates at 130 meV for 0.1 ≤ x ≤ 0.6. Compositional dependent tunability of the above discussed parameters may open a constructive approach to design low energy-loss and high-resistive electromagnetic elements for microwave devices which is the key significance of the present study.

Ordered Ti-doped FeVO4 nanoblock photoanode with improved charge properties for efficient solar water splitting

Highly photoactive FeVO4 photoanodes with ordered nanoblock morphology and uniform Ti-doping were prepared by drop-casting mixed Ti and V precursors onto FeOOH nanorod films and following an annealing process. The results indicate that Ti4+ is uniformly doped into the FeVO4 lattice by substituting V5+ and provides an increased number of O2– vacancies. The optimized film thickness and doping level are 620 nm and 0.3%, respectively. Compared to the undoped sample, the Ti-doped photoanode showed ~ 219% enhancement in photocurrent at 1.0 V vs Ag/AgCl under back illumination of AM 1.5, reaching a state-of-the-art value of ~ 1.47 mA cm−2, and also achieved stable and efficient overall water splitting activity with evolution rates of 28.3 and 14.1 μmol cm−2h−1 for H2 and O2, respectively. The excellent PEC performance could be attributed to the remarkably enhanced charge carrier concentration and conductivity, and the facilitated charge transfer kinetics across the semiconductor/electrolyte interface, as a result of Ti-doping.

Fabrication and Properties of Graphene Electron Multiple Transporting Layers for Dye-Sensitized Solar Cell

To investigate the optimal working electrode for dye-sensitized solar cells (DSSCs), the traditional TiO2 film is modified by adding an electron transporting layer of graphene. Different layers of TiO2/graphene/TiO2 stacks on the FTO substrate are analyzed. The experimental results show that the TiO2/graphene/ TiO2/graphene/TiO2 (TGT2) structure has higher dye loading, which means that more dye molecules can increase the light absorption. In the electrochemical impedance spectroscopy (EIS) analysis, the TGT2 structure has a lower interfacial resistance ( R ct2) of 2.35 Ω at the TiO2/dye/electrolyte interface and a higher electron lifetime (τe) of 64.28 ms. This result represents that the graphene material exerts its properties of good conductivity and high charge carrier mobility to reduce the interfacial resistance and enhance the electron transport capability. The DSSCs with TGT2 structure working electrode has the short circuit current density ( J SC) of 10.87 mA/cm2 and photovoltaic conversion efficiency (η) of 4.47%. In this study, the working electrode of DSSC is successfully modified by using a TGT2 structure, with an improved efficiency of 10.6% and short circuit current density ( J SC) of 17.7% higher than that of the TiO2 working electrode.

Retracted: Development of a Highly Sensitive Wearable Tactile Sensor on Fabric by Using Conductive Inks Based on Electrical Contact Resistance (ECR) Change Mechanism

AbstractA wearable tactile device, based on the electrical contact resistance (ECR) between the two fabric substrates, is developed in this work for continuous health monitoring. Microscale pillar structures are formed over top and bottom fabric substrates by screen‐printing technique with conductive inks followed by the face‐to‐face assembly of top and bottom parts. The contact areas between the substrates increase after the application of an external force, resulting the increment of charge carrier conduction and reduction in ECR value. To enhance the sensitivity, the device is optimized with two different conductive inks (i.e., silver and graphene inks) to create pillar shaped microstructures resulting a higher sensitivity due to the variation in ECR. This wearable tactile sensor's practical applications also are investigated in monitoring human wrist pulses with wireless module and smartphone, showing its capability in faster response and high sensitivity for internet‐of‐thing and medical applications.

Mechanism of Na-Ion Conduction in the Highly Efficient Layered Battery Material Na2Mn3O7

The ionic conduction properties of the technologically important two-dimensional (2D) layered battery material Na2Mn3O7, with exceptional small-voltage hysteresis between charge and discharge curves, have been investigated as a function of temperature and frequency by an impedance spectroscopy. The detailed analyses of the impedance data in the form of dc-conductivity, ac-conductivity, electrical modulus, dielectric constant and complex polarizability reveal a long-range Na-ionic conductivity with negligible contribution from a local dipole relaxation. A significant enhancement (~10^4 times) of the Na-ion conductivity has been found with the increasing temperature from 353 K to 713 K. The temperature dependent conductivity reveals thermally activated conduction process with activation energies of 0.161 and 0.377 eV over the two temperature regions of 383-518 K and 518-713 K, respectively. AC conductivity study reveals a long-range hopping process for the conduction of charge carriers with a sharp increase of the hopping range at 518 K. The scaling study of the ac-conductivity reveals that the frequency-activated conductivity (above 10^4 Hz at 353 K) is mainly controlled by the critical frequency that increases with the increasing temperature. The Na-ion conduction in Na2Mn3O7 occurs predominantly by a correlated barrier hopping process. Besides, a correlation between ionic conduction and crystal structure has been established by x-ray and neutron diffraction study. We have further shown that the conductivity of Na2Mn3O7 can be enhanced by reduction of the stacking faults in the crystal structure. Our study facilitates the understanding of the microscopic ionic conduction mechanism in the highly efficient 2D battery material Na2Mn3O7 having high energy storage capacity and high structural stability, paving way for the discovery of materials for battery applications.

Elevating the charge separation of MgFe2O4 nanostructures by Zn ions for enhanced photocatalytic and photoelectrochemical water splitting

Magnesium ferrites (MgFe2O4) are important class of ferrites that have been receiving greater attention as promising excellent photocatalyst due to its low cost, wide light spectrum response and environment-friendly nature. However, its poor electronic conductivity and fast charge carrier recombination hinders its electrocatalytical applications. Hence, accelerating charge carriers separation efficiency is important to modify the photoelectrochemical performance of MgFe2O4. Herein, novel Zn ions doped MgFe2O4 nanospheres are fabricated for the first time. Zn ions are doped into MgFe2O4 nanostructures from surface to enhance their charge separation efficiency. The doped MgFe2O4 nanostructures show significant photocatalytic activity and enhanced photocurrent density than that of pristine MgFe2O4.The improved photoelectrocatalytic performance is attributed to doping effect, were Zn ions actually enhance the conductivity. Zn ions enhance the activity of MgFe2O4 and accelerate the charge transfer properties in MgFe2O4. The results highlight that Zn doped MgFe2O4 nanospheres could be a potential candidate for photocatalytic and photoelectrochemical applications.

Temperature dependency of excitonic effective mass and charge carrier conduction mechanism in CH3NH3PbI3\u2212xClx thin films

In this paper we explain the temperature dependence of excitonic effective mass and charge carrier conduction mechanism occurs in CH3NH3PbI3−xClx thin films prepared by chemical dip coating (CDC), spray pyrolysis (Spray) and repeated dipping-withdrawing (Dipping). Hall Effect study confirmed that prepared CH3NH3PbI3−xClx samples are p-type semiconductor having carrier concentration of the order of ~ 1016 cm−3. The charge carrier mobility, mean free path and mean free life time were found to decrease with increasing temperature due to polaronic effect. The excitonic effective mass is estimated to (0.090–0.196)me and excitonic binding energy (15–33) meV, well consistent with Wannier-Mott hydrogenic model and the nature of exciton is likely to be Mott-Wannier type. From electrical measurement, it was observed that charge carrier conduction in CH3NH3PbI3−xClx is governed by migration of {mathrm{I}}^{-} and CH3N {mathrm{H}}_{3}^{+} vacancies and vacancy-assisted diffusion processes depending on temperature.

Plasma-assisted deposition of indium tin oxide thin films by sublimation using an anodic vacuum arc discharge

With the anodic vacuum arc discharge as a method of physical vapor deposition (PVD) excellent properties of thin transparent conductive oxide films can be achieved, but the relations between the process parameters and the coating properties have been insufficiently described in the literature. This paper is intended to narrow this gap by investigations on indium tin oxide (ITO) thin films deposited on borosilicate glass sheets by sublimation of indium tin oxide (90:10) using an anodic vacuum arc. The arc discharge is based on a hot hollow cathode electron source and a special evaporator connected as anode. The concentration of the discharge onto the sublimating material is achieved by combining the magnetic fields of an axially symmetrical permanent magnet system and a solenoid coil. Coating rates of about 15 nm/s were achieved with an arc current of 60 A. Measurements with a planar Langmuir probe have shown that the vapor is highly ionized (about 95%). The discharge voltages are relatively low (< 60 V), so it can be assumed that the particle energies are correspondingly low. Substrate temperature (30–300 °C), oxygen gas flow (0–100 sccm) and gas pressure (0.04–0.4 Pa) were varied to study their influence on the thin film properties. Specific electrical conductivity, density and mobility of charge carriers, as well as optical properties were determined and compared with those of other PVD processes. Low specific electrical resistance of 1.8–2.0 x 10–4 Ω cm was reached at a substrate temperature of 200–300 °C independently of the pressure. The mean optical transmission (in the spectral range between 400 nm and 1100 nm) of 100 nm thick ITO films deposited at a temperature of 200 °C and at an optimized oxygen flow was determined to 84%. The roughness of the layers determined by atomic force microscopy is significantly lower than typically for magnetron sputtered films. At a pressure of 0.04 Pa, the crystalline bixbyite phase can already be detected at a coating temperature of approx. 30 °C, whereby the layer growth begins with the formation of an amorphous structure and changes to the crystalline phase with increasing layer thickness. At a temperature above 100 °C and low coating pressure the layers are completely crystalline. At a higher pressure the transition from amorphous to crystalline phase is shifted towards higher temperature. For lower oxygen flows the crystallites exhibit mainly a preferred (211) orientation. For higher oxygen flows the texture of crystallites is changed and the intensity of (440) and (622) is increased. The formation of these special crystallographic textures can probably explain the very low roughness values of the ITO layers measured by atomic force microscopy. The investigations have shown how the film properties can be adjusted by the process parameters and that the ITO sublimation using an anodic vacuum arc is suited very well for plasma assisted ITO thin film deposition.

Long carrier lifetimes in crystalline lithium tetraborate

Long carrier lifetimes were extracted from current-voltage and capacitance-voltage characteristics of the X-cut and Z-cut lithium tetraborate Li2B4O7. It is further revealed that the carrier lifetime along the [001] direction is almost six times the carrier lifetime along the [100] direction, which is consistent with the well-established highly anisotropic charge carrier conduction in the tetragonal Li2B4O7. Thus, the reported long carrier lifetimes project Li2B4O7 as a potential candidate for complete solid-state detector applications.

Effects of Non-magnetic Metallic Zinc Nanoparticles on the Dielectric Properties of CuTl-1223 Superconducting Phase

Synthesis of non-magnetic metallic zinc (Zn) nanoparticles (NPs) and (Zn)x/Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) nanoparticle-superconductor composites was carried out by chemical sol-gel and solid-state reaction methods, respectively. Different concentrations of Zn NPs from 1.0 to 4.0 wt.% were inserted in CuTl-1223 superconducting matrix to obtain desired (Zn)x/CuTl-1223 nanoparticle-superconductor composites. The structural properties of these NPs and composites were studied by X-ray diffraction (XRD) technique. The unaffected crystal symmetry of the host CuTl-1223 superconducting phase after the inclusion of Zn NPs from XRD patterns suggested that these NPs were settled across the grain boundaries. Transport electrical properties of (Zn)x/CuTl-1223 composites were investigated by resistivity versus temperature (RT) measurements, and zero resistivity critical temperature (Tc) was found to be increased with Zn NPs contents up to x = 3 wt.%. The enhancement in Tc could be due to the non-magnetic metallic Zn 3d10 (S = 0) NPs that facilitated the conduction of charge carriers across the grain boundaries, while Tc was suppressed beyond x = 3 wt.% contents of Zn NPs due to reduced superconducting volume fraction of CuTl-1223 matrix. Using the LCR meter, dielectric parameters, namely real part (ɛ/r), imaginary part (ɛ//r), tangent loss (tanδ), and ac-conductivity (σac), were measured at varying frequencies and temperatures. The values of ɛ/r, ɛ//r and tanδ were found to be maximum at lower frequencies and became constant at high frequencies, while the value of σac was found to be minimum at lower frequencies and was increased with increasing frequency.

Understanding the structure and charge transport mechanism of Sm2NiMnO6 double perovskite prepared via low temperature auto-ignition method

This study investigates the structure and conduction mechanism of Sm2NiMnO6 prepared via auto-ignition method. Rietveld refinement of the XRD pattern confirms the monoclinic structure with space group P21/n. This crystal structure is discussed in details. The room temperature conductivity is 1.6×10−6Ω−1cm−1. The values of total activation energy, dc activation energy, hoping energy and migration energy are 0.43 eV, 0.44 eV, 0.43 eV and 0.43 eV respectively. The closed value of all activation energy confirms the conduction of charge carriers via hopping mechanism. Variable range hopping model confirms the small polaron hopping in the material.

Effect of vanadium doping on the electrical charge transport and dielectric relaxation properties of Sodium Bismuth Titanate perovskite

In this work, we report the effect of vanadium doping on the conductivity and relaxation dynamics of the charge carriers in Sodium Bismuth Titanate perovskite material (Na0.5Bi0.5TiO3) prepared by a unique technique which is a combination of chemical and mechanical methods. The parent material was prepared using the citrate auto-ignition method and the mechanical alloying technique was used to incorporate V2O5 in the NBT structure. The X-ray diffraction analysis confirmed the formation of the rhombohedral phase of NBT perovskite with space group R3c in all the compositions. The microstructural analysis was done using Field Emission Scanning Electron Microscopy, Energy-dispersive X-ray spectra, and the elemental mapping of the samples. The conductivity mechanism was analyzed using the complex impedance method. The sample with 15% doping showed the highest conductivity with minimum activation energy. The activation energies for conduction, relaxation, and migration of charge carriers were found to be comparable with each other. The frequency-dependent dielectric data was analyzed using Havriliak–Negami (HN) formalism and suggested non-Debye type relaxation behaviour. The 15% dopped composition showed the highest dielectric strength. The scaling behaviour of impedance and modulus spectra confirmed the temperature-independent conduction and relaxation mechanisms.

Graphene and graphene‐like structure from biomass for Electrochemical Energy Storage application‐ A Review

AbstractGraphene, an SP2 hybridized 2‐D atomic crystal, has been one of the most significant materials of the current century. Researchers in the recent years find graphene to be highly appealing for its superlative electrochemical energy storage applications and some of its unique features such as fractional quantum hall effect which is even exhibited in normal temperatures such as room temperature, ballistic conduction of charge carriers along with the exhibition of ambipolar electric field effect and modifiable bandgap. Enhanced electrochemical performances have been achieved by coalescing graphene with other electrochemical materials. This review focuses on various bio‐precursors involved in the synthesis of graphene and its diverse production methods along with their merits and demerits. It also summarizes the ensuing features and macro‐structural complexity of the graphene‐derived structural composites as well as its applications as competent electrode material in energy storage devices. It specifically endeavors in providing a comprehensible idea on the availability of a variety of biomass sources and its synthesis techniques for a better and optimized mass production of graphene with uncompromising purity as well as the perspectives of the graphene‐based composites that pave path for its improved application in advanced storage devices. This review article casts light upon the enormous opportunities of graphene production with easy synthesizing techniques that could aid in the fabrication of high performance of supercapacitors.

Magnified charge carrier conduction, permittivity, and mesomorphic properties of columnar structure of a room temperature discotic liquid crystalline material due to the dispersion of low concentration ferroelectric nanoparticles.

Liquid crystal nanocomposites have been a hot topic of research due to optimization of physical properties with such blending. There are several reports on enhancement of physical properties of nematic liquid crystals due to the blending of the nanomaterials. L. M. Lopatina and J. V. Selinger [Phys. Rev. Lett. 102, 197802 (2009)]10.1103/PhysRevLett.102.197802 have even proposed a theory based on experimental results for the enhancement of the properties of the nematic mesophase in the presence of ferroelectric nanoparticles. However, discotic liquid crystal nanocomposites are less studied. In the present experimental work, we have studied the effect of ferroelectric (BaTiO_{3}) nanoparticles on a room temperature discotic liquid crystalline material, namely 1,5-dihydroxy-2,3,6,7-tetrakis(3,7-dimethyloctyloxy)-9,10-anthraquinone. We investigated the physical properties of low concentration ferroelectric nanoparticle dispersed discotic columnar structure, using calorimetric, optical, x-ray diffraction, and dielectric spectroscopy tools. Results show that inclusion of ferroelectric nanoparticles in the discotic matrix consolidates the stability of the columnar matrix of the Col_{h} phase by virtue of their ferroic nature. An enhancement in charge carrier conductivity by several orders of magnitude at ambient conditions has been observed which makes such systems highly appropriate for one-dimensional conductors. Low concentration of BaTiO_{3} nanoparticles substantially enhanced permittivity of the system also. A molecular relaxation mode has been observed in the middle frequency range of the dielectric spectra. Enhancement of these important parameters could be possible due to the ferroelectric nature of the dispersed nanoparticles.

(Invited) Steam Electrolysis Using Proton-Conducting Perovskites: Prospects and Challenges

This paper demonstrates and discusses steam electrolysis performance using proton-conducting solid oxide materials with respect to the benefit and prospects as well as challenges toward the technical application for hydrogen production.Water electrolysis will take an important role as the energy storage for the vast use of renewable energy. Steam electrolysis is characterized by high energy conversion efficiency compared to low temperature water electrolysis. However, the conventional technique is accompanied by high operation temperature because the ionic conduction in solids needs high temperature. As a mean to reduce the operation temperature, the proton conducting perovskite is thus a choice for the electrolyte since it works in intermediate-temperature regime. We have reported so far SrZr0.5Ce0.4Y0.1O3-δ (SZCY541) [1] and BaZr0.44Ce0.36Y0.2O3-δ (BZCY(54)8/92) [2] to be highly proton conducting and sufficiently stable in steam at the inter mediate temperatures. The latter exhibits the conductivity of 10-2 S/cm in moist hydrogen at 500°C and has been demonstrated as the electrolyte for steam electrolysis [3].The most remarkable difference of proton conductors from other solid electrolytes is the mechanism for the generation of proton conducting charge carriers. It takes place as a result of hydration of oxide ion vacancies. One of the challenges for the material is the volumetric deformation accompanied by hydration/dehydration that possibly leads fatigue of the cell structure. Another is originated from the defect chemistry, that is the hydration is competing with oxygen incorporation to the oxide ion vacancy that result in the electronic hole formation in oxidative atmosphere. Electronic leakage, reduction of Fardaic efficiency, is originated from this hole conductivity intrinsically being in the materials. Mixed-conducting electrode materials are still under investigation by many researchers. Another issue is the inter-diffusion of transition metal species from the electrodes to the electrolyte causing the reduction of the proton conductivity. These challenges will be discussed for improving the reliability of the proton conductor steam electrolysis. AcknowledgementThis work was supported by the Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "energy carrier" (Funding agency: JST), the JSPS-NSF Partnerships for International Research and Education (PIRE), the JSPS Core-to-Core Program of Advanced Research Networks (Solid Oxide Interfaces for Faster Ion Transport), METI International joint research and development of innovative energy technology, JST SICORP, and World Premium International Research Center Initiative (WPI), MEXT Japan.

Experimental Studies on the Dynamic Memcapacitance Modulation of the ReO3@ReS2 Composite Material-Based Diode.

In this study, both memcapacitive and memristive characteristics in the composite material based on the rhenium disulfide (ReS2) rich in rhenium (VI) oxide (ReO3) surface overlayer (ReO3@ReS2) and in the indium tin oxide (ITO)/ReO3@ReS2/aluminum (Al) device configuration is presented. Comprehensive experimental analysis of the ReO3@ReS2 material properties’ dependence on the memcapacitor electrical characteristics was carried out by standard as well as frequency-dependent current–voltage, capacitance–voltage, and conductance–voltage studies. Furthermore, determination of the charge carrier conduction model, charge carrier mobility, density of the trap states, density of the available charge carrier, free-carrier concentration, effective density of states in the conduction band, activation energy of the carrier transport, as well as ion hopping was successfully conducted for the ReO3@ReS2 based on the experimental data. The ITO/ReO3@ReS2/Al charge carrier conduction was found to rely on the mixed electronic–ionic processes, involving electrochemical metallization and lattice oxygen atoms migration in response to the externally modulated electric field strength. The chemical potential generated by the electronic–ionic ITO/ReO3@ReS2/Al resistive memory cell non-equlibrium processes leads to the occurrence of the nanobattery effect. This finding supports the possibility of a nonvolatile memory cell with a new operation principle based on the potential read function.

First principle studies on the structural and optoelectronic properties of boron antimonide: A promising candidate for photovoltaic applications

The search for a superior material with greater energy conversion efficiency as compared to the existing material systems for photovoltaic applications has always been the quest of research community. A systematic study of the optoelectronic properties of zinc blende (ZB) phase boron antimonide (BSb) using the full-potential linearized augmented plane wave (FPLAPW) basis sets in the density functional theory (DFT) with the Modified Becke-Johnson (mBJ) exchange correlation (XC) potential is carried out to investigate its potential as a photovoltaic material. Structural optimization is done considering the Perdew-Burke-Ernzerh of generalized gradient approximation (PBEsol) XC functional. Taking into account the optimized lattice constant of 5.2306 Å, which is consistent with previous experimental as well as theoretical findings, the fundamental electronic and optical parameters such as electronic density of state (DOS), band diagram, complex-dielectric function, refractive index, extinction coefficient, and optical absorption coefficient are computed. The effective mass of charge carriers for conduction and valence band have been calculated along the crystallographic symmetric directions. The calculated wider direct-gap (Γ−Γ) of 2.8048eV, and a comparatively narrower indirect-gap (X−Γ) of 0.99694eV are in excellent agreement with the available literature. These distinct and fascinating optoelectronic properties of BSb can be very useful for realizing solar cells with better energy conversion efficiency.

Highly stable perovskite solar cells based on perovskite/NiO-graphene composites and NiO interface with 25.9 mA/cm2 photocurrent density and 20.8% efficiency

Perovskite solar cells (PSCs) demonstrated a record-high power conversion efficiency, but they have instability issues attributed to the degradation of materials and device performance. To overcome the instability problem and performance degradation, various methods have been proposed, but still need a comprehensive solution. Here, we propose an innovative way of insuring device performance and long-term stability by utilizing functional composites of perovskite, nickle oxide and graphene into device structures. We fabricated the PSCs based on MAPbI 3−x Cl x /NiO-graphene photoactive composite and NiO interface layer. Compared to the pristine perovskite cells, the champion device based on the photoactive composites with NiO interface showed remarkably high photocurrent density of 25.9 mA/cm 2 (i.e., 95.2% of theoretical maximum) and power conversion efficiency of 20.8% without J-V hysteresis. More impressively, unencapsulated cells showed significant improvement of thermal- and photo- and long-term air-stability with retaining 97–100% of the initial values of performance parameters over 310 days under ambient conditions. Schematic illustration of a perovskite solar cell structure based on MAPbI 3−x Cl x /NiO-rGO composite photoactive layer and NiO interface formed on the SrTiO 3 /Al 2 O 3 -graphene electron transfer layer, exhibiting the mechanism of charge carrier separation and conduction through graphene and connected NiO nanoparticles and blocking moisture and oxygen infiltration. • Highly stable and efficient composites-based perovskite solar cells. • Perovskite/NiO-graphene photoactive composite and NiO interface layer. • Remarkably high photocurrent density and power conversion efficiency without J-V hysteresis. • Significant improvement of thermal- and photo- and air-stability with retaining 97–100% of device performance over 310 days.

Three-Dimensional Variable Range Hopping and Thermally Activated Conduction Mechanism of Polypyrrole/Zinc Cobalt Oxide Nanocomposites

Zinc cobalt oxide (ZCO) nanoparticles and zinc cobalt oxide/polypyrrole (ZCO/PPy) nanocomposites were synthesized by hydrothermal and in situ chemical polymerization routes, respectively. X-ray diffraction (XRD) patterns of PPy and ZCO/PPy nanocomposites show the amorphous nature of PPy, while there is the presence of dominant crystalline peaks of ZCO in the PPy matrix. Field-emission scanning electron microscopy (FESEM) depicts a spherical geometry and shows a decrease in the particle size with an increase in the ZCO weight percentage, while the transmission electron microscopy (TEM) images depict the core–shell-type formation of particles with aggregated ZCO nanoparticles as a core embedded in the PPy shell. The Fourier transform infrared (FTIR) spectra of ZCO/PPy nanocomposites show all the asymmetrical stretching vibrations of PPy and ZCO along with an increase in intensities of the respective metal oxides peaks and slight shifts in a few bands. Further, the transport studies, i.e., direct current (DC) conductivities of the ZCO/PPy nanocomposites, were studied as a function of temperature (300–453 K) and reveal semiconducting transport behavior. The analysis of DC conduction in PPy and ZCO/PPy suggests that the conduction of charge carriers follows the three-dimensional Mott variable range hopping (3D-VRH) model at a lower temperature, while it follows a thermally activated conduction model at high temperature.