Simple indoline based donor–acceptor dye for high efficiency dye-sensitized solar cells

A simple metal-free donor–acceptor type sensitizer U01, bearing strong electron donor indoline-triphenylamine was synthesized for panchromatic sensitization of TiO₂ nanocrystalline film. Photovoltaic properties of U01 showed remarkably enhanced light harvesting due to the presence of strong electron donor and robust structure. The new U01 sensitized solar cell exhibited a photovoltaic performance: a short-circuit photocurrent density (J_sc) of 10.70 mA cm⁻², an open-circuit photovoltage (V_oc) of 0.758 V and a fill factor (FF) of 0.74, corresponding to an overall conversion efficiency of 6.01% under standard global AM 1.5 solar light condition. Our results suggest that indoline-triphenylamine based robust D–A molecular architecture is a highly promising class of panchromatic sensitizers for improvement of the performance of dye-sensitized solar cells (DSCs).     

Ionic conductivity in the ternary system (ZrO2)1−0.08x−0.12y–(Y2O3)0.08x–(CaO)0.12y

The total electrical conductivity of the samples in the ternarysystem (ZrO₂)_{1-0.08x-0.12y} –(Y₂O₃)_0.08x –(CaO)_0.12y was measured by adirect current four-probe method in the temperature range 773 to1673 K. It was found that partial replacement of Y₂O₃ by CaO in thesystem ZrO₂–Y₂O₃ may enhance the electrical conductivity at highertemperatures. At lower temperatures, however, doping CaO as the thirdcomponent into the system ZrO₂–Y₂O₃ depresses the conductivity. Theobserved mixed dopant effect was then analyzed by considering thecombined effect of both parameters appeared in the traditionalArrhenius equation, the activation energy, E, and the preexponentialfactor, ₀, on the temperature-dependence of the measured conductivity.     

Thermoelectric properties of Bi1−xSbx films with 0 < x ⩽ 0.3

The electrical conductivity, its temperature coefficient and the thermoelectric power of Bi_1−xSb_x films with 0 < x ⩽ 0.3 and thicknesses from 20 to 400 nm were measured in the temperature range 80–400 K. The results are discussed in the framework of a previously proposed anisotropic non-degenerate two-band model.     

Synthesis and thermoelectric characterization of polycrystalline Ni1−x Ca x Co2O4 (x=0–0.05) spinel materials

Ca doped NiCo₂O₄ spinel materials were synthesized by conventional solid state reactions at 900 °C. Thermoelectric properties of polycrystalline products were characterized at high temperature range of 800 °C in air. d.c. conductivity of the prepared polycrystalline 5 mol % Ca doped NiCo₂O₄ was about 60 S m^–1 at 300 °C. The value of d.c. conductivity was increased with the temperature increasing. Thermoelectric voltage of polycrystalline Ni_1–x Ca _x Co₂O₄ (x=0–0.05) was positive at 300–800 °C, this showed p-type thermoelectric properties. The Seebeck coefficient of 5 mol % Ca doped NiCo₂O₄ was ca. 300 V/K at 600 °C. The value of the Seebeck coefficient of Ni_1–x Ca _x Co₂O₄ polycrystalline products decreased with the increasing temperature. Thermal conductivity of 5 mol % Ca doped NiCo₂O₄ was ca. 2.2 W m^–1 K^–1 at 600 °C. The estimated thermoelectric figure-of-merit, Z, of 5 mol % Ca doped NiCo₂O₄ spinel polycrystalline product was about 3.5×10^–5 K^–1 at 600 °C.     

A study of the magnetocrystalline anisotropy of Sm1−xDyxFe10.5Mo1.5(x = 0–1.0)

The magnetocrystalline anisotropy and the spin reorientation of Sm_1–xDy_xFe_10.5Mo_1.5 were investigated in detail. At room temperature, all Sm_1–xDy_xFe_10.5Mo_1.5 alloys possess easy c-axis anisotropy and the magnetocrystalline anisotropy field decreases with increasing Dy concentration. However, at low temperature, a spin reorientation transition of axis-to-cone type was observed in the Sm_1–xDy_xFe_10.5Mo_1.5 alloys with x0.8. The spin reorientation temperatures increase with increasing Dy concentration in the Sm_1–xDy_xFe_10.5Mo_1.5 alloys.     

Preparation of the single phase γ′-(Fe1−x Ni x )4N compounds (0 ≤x ≤ 0.6)

Single phase -Fe₄N type (Fe_1–xNi_x)₄N compounds (0 x 0.6 have been synthesized for the first time by controlled heat treatment of iron-nickel oxalates in a gaseous flow of NH₃ xand H₂. The preparation processes were investigated using differential scanning calorimetry (DSC), X-ray diffraction and Mössbauer spectroscopy. The results confirmed that annealing of oxalates in the NH₃ and H₂ atmosphere included the processes of dehydration, decomposition and reduction, nitrogenation and thermal decomposition of the nitrides. The decomposition and reduction occur simultaneously. The final products depend on the flow rate ratio of NH₃ H₂ and the annealing temperature. The formation conditions for the single phase -Fe₄N type (Fe_1–xNi_x)₄N compounds are related to the nickel concentration, with increasing nickel content, the nitrogenation temperature decreased, in contrast the flow rate ratio of NH₃ H₂ increased.     

Fabrication of n-Zn1−xGaxO/p-(ZnO)1−x(GaP)x thin films and homojunction

Ga doped ZnO (GZO) and GaP codoped ZnO (GPZO) thin films of different concentrations (1–4 mol%) have been grown on sapphire substrates by RF sputtering for the fabrication of ZnO homojunction. The grown films have been characterized by X-ray diffraction (XRD), photoluminescence (PL), Hall measurement, energy dispersive spectroscopy (EDS), time-of-flight secondary ion mass spectrometer (ToF-SIMS), UV–Vis–NIR spectroscopy and atomic force microscopy (AFM). Unlike in conventional codoping, here we directly doped (codoped) GaP into ZnO to realize p-ZnO. The Hall measurements indicate that 2 and 4% GPZO films exhibit p-conductivity due to the sufficient amount of phosphorous incorporation while all the monodoped GZO films showed n-conductivity as expected. Among the p-ZnO films, 2% GPZO film shows low resistivity (2.17 Ωcm) and high hole concentration (1.8 × 10¹⁸ cm^?3) by optimum incorporation of phosphorous due to best codoping. Similarly, among the n-type films, 2% GZO shows low resistivity (1.32 Ωcm) and high electron concentration (2.02 × 10¹⁹ cm^?3) by optimum amount of Ga incorporation. The blue shift and red shift in NBE emission observed from PL acknowledged the formation of n- and p-conduction in monodoped and codoped films, respectively. The neutral acceptor bound exciton recombination (A⁰X) observed by low temperature PL for 2% GPZO confirms the p-conductivity. Further, the high concentration of P atoms than Ga observed from ToF-SIMS (2% GPZO) also supports the p-conductivity of the films. The fabricated p–n junction with best codoped p-(ZnO)_0.98(GaP)_0.02 and best monodoped n-Zn_0.98Ga_0.02O films showed typical rectification behavior of a diode. The diode parameters have also been estimated for the fabricated homojunction.     

Crystallization kinetics of Zr-rich FexZr0−x0−x0−x(20 ⩽ x ⩽ 40) metallic glasses

The crystallization kinetics of the melt-spun Fe-Zr metallic glasses in the iron-rich region has been investigated by means of DSC and X-ray diffraction. The crystallization mode changes with iron concentration. In the lower iron region, 20 x 25, the Fe _x Zr100–x glasses crystallize into -Zr and Ti₂Ni-type FeZr₂ with an accompanying sharp and large exotherm at the first crystallization step and immediately after this step, they transform into orthorhombic FeZr₃. On the other hand, the alloys with 35 x 40 exhibit a gradual exotherm which initiates from a temperature far below the definite crystallization temperature (T _x). The Fe-Zr metallic glasses in this concentration region crystallize polymorphously into the oxygenstabilized Ti₂Ni-type FeZr₂ with accompanying relatively small and composite exotherms. The annealing at a temperature where the gradual exotherm occurs for the alloys with 30 x 40 does not cause any changes of X-ray halo pattern but results in the reduction of the heat of exotherm due to the crystallization.     

Hydrogen sorption properties of V1 − x Cr x (x = 0.1–0.5) alloys

We have studied the interaction of hydrogen with vanadium-chromium alloys. Hydrogen absorption and desorption isotherms have been constructed, the stability ranges of the forming hydride phases have been determined, and the ΔH and ΔS of the reactions involved have been evaluated. X-ray diffraction characterization results indicate the formation of three hydride phases, with fcc, bcc, and hcp structures.     

Photovoltaic performance of dye-sensitized solar cells fabricated with polyvinylidene fluoride–polyacrylonitrile–silicondioxide hybrid composite membrane

Electrospun fibrous membranes of hybrid composites of polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN) and silicon dioxide (SiO₂) (PVdF–PAN–SiO₂) are prepared with different proportions of SiO₂ (3, 5 and 7% w/w). The field emission scanning electron microscopy (FE-SEM) reveals that these membranes have three-dimensional, fully interconnected network structures, which are combined with micropores of fine SiO₂ distribution. The surface roughness of the membranes increases with increasing the SiO₂ content. It is found that 7 wt% SiO₂/PVdF–PAN electrolyte membrane has the highest ionic conductivity (6.96 × 10⁻² S cm⁻¹) due to the large liquid electrolyte uptake (about 570%). As the concentration of SiO₂ nanoparticles increase, the contact angle value also increases, ranging from 135.70° to 140.60° which indicates that the membrane has higher hydrophobicity. The dye sensitized solar cells (DSSCs) are fabricated using the hybrid composite membrane with PVdF–PAN with 7 wt % SiO₂. Its photovoltaic performance exhibits an open circuit voltage (V_oc) of 0.79 V and a short circuit current 11.6 mA cm⁻² at an incident light intensity of 100 mW cm⁻², producing an efficiency of 5.61%. DSSC, using the hybrid composite electrospun membrane which shows more stable photovoltaic performance than other assembled DSSCs.     

Electrical properties of (Ni1−x )Li x )O (x=0.1 and 0.2) under various relative humidities

Rocksalt-type (Ni_1–x Li _x )O (x=0.1 and 0.2) was synthesized at 1350° C in air and its electrical resistivity (R) was measured under various relative humidities (H). R increases with increasing H in the range 0H79%, reaches a maximum value, then decreases in the range 79%<H100%. The increase in R is explained by an electron boundary layer model. On the other hand, the decrease in R is explained by ionic conductivity.     

Structural and optical properties of Cd x Zn(1 − x)Te thin films

Seven Cd _x Zn_{(1 ? x} Te solid solutions with x = 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 were synthesized by fusing stoichiometric amounts of CdTe and ZnTe constituents in silica tubes. Each composition was used in the preparation of a group of thin films of different thicknesses. Structural investigation of the obtained films indicates they have a polycrystalline structure with predominant diffraction lines corresponding to (111) (220) and (311) reflecting planes, which can be attributed to the characteristics of growth with the (111) plane. The optical constants (the refractive index n, the absorption index k, and the absorption coefficient α) of Cd _x Zn_{(1 \s -x)} Te thin films were determined in the spectral range 500–2000 nm. At certain wavelengths it was found that the refractive index, n, increases with increasing molar fraction, x. It was also found that plots of α² (hv) and α^1/2 (hv) yield straight lines, corresponding to direct and indirect allowed transitions respectively obeying the following two equations: $$\begin{gathered} E_g^d = 1.583 + 0.277x + 0.197x^2 \hfill \\ E_g^{ind} = 1.281 + 0.111x + 0.302x^2 \hfill \\ \end{gathered}$$      

Effect of the composition and annealing conditions of precursor films on the structure of thin CuIn1 − x GaxSe2 (0 ≤ x ≤ 0.7) layers

A technique has been developed for the preparation of CuIn _x Ga_{1 ? x} Se₂ layers through closed-space selenization of precursor films containing intermetallic compounds. We also have produced CuIn _x Ga_{1 ? x} Se₂ films by selenizing metallic precursor films. Examination of the CuIn _x Ga_{1 ? x} Se₂ layers by X-ray diffraction, atomic force microscopy, and scanning electron microscopy has shown that the use of inter-metallic precursors offers a number of important advantages: phase purity and homogeneity of CuIn _x Ga_{1 ? x} Se₂ layers, in combination with good adhesion of the layers to substrates (glass or glass/molybdenum).     

Photoelectrochemical solar (PES) cells with Cd1−xPbxSe polycrystalline thin film electrodes

An electrochemical solar cell behavior of a mixed type n-Cd_1–x Pb _x Se (0x0.5) thin film electrode is presented in this paper. A series of the electrodes were prepared for the values of x in the above range and the electrochemical cells of the configuration n-Cd_1–x Pb _x Se/K₄Fe(CN)₆/C were fabricated. The current–voltage and capacitance–voltage characteristics of the as-fabricated cells in dark were examined to understand nature of the charge transfer process across the electrode/electrolyte interface. These cells were then illuminated with a light of 20 mW cm^–2 intensity and the power output curves were obtained and analyzed. Both open circuit voltage (V_oc) and short circuit current (I_sc) found boosted enhancing the power conversion efficiency (%) from 0.065% to 0.28% at x=0.1. The flat band potentials (V_fb) were also determined for these cells and it is found to attain a maximum value at x=0.1. The other cell parameters were estimated and showed improvement in the overall performance of a cell. Attempts were made to explain the observed results through modified electrode properties.     

Plastic behaviour of Cd x Hg1−x Te (0⩽ x⩽1) crystals

Cd _x Hg_1–x Te (0x1) single crystals were strained by microhardness and by constant strain rate uniaxial compression tests, in the temperature range 300 to 600 K. Hardness curves as function of temperature can be described by empirical relations. Stress-strain curves, relaxation tests and dislocation observations using transmission electron microscopy show that the deformation is controlled by a thermally activated Peierls mechanism. Moreover, dislocations are dissociated with a stacking fault energy which does not depend on thex composition.