Enhancing Fullerene‐Based Solar Cell Lifetimes by Addition of a Fullerene Dumbbell

Cost‐effective, solution‐processable organic photovoltaics (OPV) present an interesting alternative to inorganic silicon‐based solar cells. However, one of the major remaining challenges of OPV devices is their lack of long‐term operational stability, especially at elevated temperatures. The synthesis of a fullerene dumbbell and its use as an additive in the active layer of a PCDTBT:PCBM‐based OPV device is reported. The addition of only 20 % of this novel fullerene not only leads to improved device efficiencies, but more importantly also to a dramatic increase in morphological stability under simulated operating conditions. Dynamic secondary ion mass spectrometry (DSIMS) and TEM are used, amongst other techniques, to elucidate the origins of the improved morphological stability.     

Isolation of a Decavanadate Cluster [H2V10O28][4-picH]4·2H2O (4-pic = 4-picoline): Crystal Structure,Electrochemical Characterization,Genotoxic and Antimicrobial Studies

The studies on polyoxovanadate clusters have received considerable attentions due to their interesting structures and extensive applications in material science and medicinal chemistry. A novel decavanadate cluster with composition [H₂V₁₀O₂₈][4-pic]₄·2H₂O has been synthesized in aqueous solution and characterized by spectral (FTIR, ⁵¹V NMR, EPR and Mass) and electrochemical studies. Single crystal X-ray crystallographic investigations indicate that decavanadate anion [H₂V₁₀O₂₈]^4? and the protonated counter cations (4-picH⁺) stabilize the crystal lattice giving a 2D sheet consolidated via extensive H-bonding interactions. Cyclic voltammetric studies indicate formation of stable quasi-reversible redox couple \( \left( {{\text{V}}^{\text{V}} \overset {} \rightleftharpoons {\text{V}}^{\text{IV}} } \right) \) in solution. The genotoxic studies employing single cell gel electrophoresis and plasmid nicking assay ascertained the non toxic nature of the compound. The complex has also been tested for in vitro antimicrobial activities against gram +ve and gram ?ve bacteria and fungi. The compound can thus be exploited as antimicrobial agent since it does not cause any toxicity or damage to DNA.     

Evaluation of radon induced lung cancer risk in occupants of the old and new dwellings of the Dera Ismail Khan City,Pakistan

In order to carry out indoor radon measurement in new and old buildings of the Dera Ismail Khan city, CR-39 based radon detectors were installed in bed rooms and sitting rooms/TV lounges in 25 (each) old and new houses and were exposed to indoor radon for 90 days. After processing, mean weighted average indoor radon concentrations in old and new houses were found to be 275 ± 33 and 86 ± 18 Bq m^?3 whereas mean annual effective doses expected to be received by the occupants were 6.86 ± 0.79 and 2.1 ± 0.43 mSv year^?1, respectively. From the measured weighted average indoor radon concentration, excess relative risk factor was calculated using the risk model of BEIR VI for the age group of 35 and 55 years. Average excess lung cancer risk was found to be 1.63 ± 0.19 and 1.35 ± 0.16 and 0.5 ± 0.10 and 0.4 ± 0.08 for old and new houses, respectively.     

Measurements of natCd(γ, x) reaction cross sections and isomer ratio of 115m,gCd with the bremsstrahlung end-point energies of 50 and 60 MeV

The flux-weighted average cross sections of ^natCd(γ, xn)^{115g,m,111m,109,107,105,104}Cd and ^natCd(γ, x)^{113g,112,111g,110m}Ag reactions were measured at the bremsstrahlung end-point energies of 50 and 60 MeV. The activation and off-line γ-ray spectrometric technique was carried out using the 100 MeV electron linear accelerator at the Pohang Accelerator Laboratory, Korea. The ^natCd(γ, xn) reaction cross sections as a function of photon energy were theoretically calculated using the TALYS-1.95 and the EMPIRE-3.2 Malta codes. Then, the flux-weighted average cross sections were obtained from the theoretical values of mono-energetic photons. These values were compared with the flux-weighted values from the present study and were found to be in general agreement. The measured experimental reaction cross-sections and integral yields were described for cadmium and silver isotopes in the ^natCd(γ, xn)^{115g,m,111m,109,107,105,104}Cd and ^natCd(γ, x)^{113g,112,111g,110m}Ag reactions. The isomeric yield ratio (IR) of ^115g,mCd in the ^natCd(γ, xn) reaction was determined for the two bremsstrahlung end-point energies. The measured isomeric yield ratios of ^115g,mCd in the ^natCd(γ, xn) reaction were also compared with the theoretical values of the nuclear model codes and previously published literature data of the ¹¹⁶Cd(γ, n) and ¹¹⁶Cd(n, 2n) reactions. It was found that the IR value increases with increasing projectile energy, which demonstrates the characteristic of excitation energy. However, the higher IR value of ^115g,mCd in the ¹¹⁶Cd(n, 2n) reaction compared to that in the ¹¹⁶Cd(γ, n) reaction indicates the role of compound nuclear spin alongside excitation energy.     

Ab-initio calculations of bandgap tuning of In1-xGaxY (Y = N,P) alloys for optoelectronic applications

The Ⅲ-V alloys and doping to tune the bandgap for solar cells and other optoelectronic devices has remained a hot topic of research for the last few decades. In the present article, the bandgap tuning and its influence on optical properties of In_1-xGa_xN/P, where (x = 0.0, 0.25, 0.50, 0.75, and 1.0) alloys are comprehensively analyzed by density functional theory based on full-potential linearized augmented plane wave method (FP-LAPW) and modified Becke and Johnson potentials (TB-mBJ). The direct bandgaps turn from 0.7 eV to 3.44 eV, and 1.41 eV to 2.32 eV for In_1-xGa_xN/P alloys, which increases their potentials for optoelectronic devices. The optical properties are discussed such as dielectric constants, refraction, absorption, optical conductivity, and reflection. The light is polarized in the low energy region with minimum reflection. The absorption and optical conduction are maxima in the visible region, and they are shifted into the ultraviolet region by Ga doping. Moreover, static dielectric constant ε₁(0) is in line with the bandgap from Penn's model.     

化学合成的钯改性的NiFe2O4纳米颗粒的结构和磁性

采用溶胶-凝胶自动燃烧方法合成了镍铁-钯复合材料NiFe₂O₄-Pd的磁性纳米颗粒. 样品在800 ℃烧结6 h生成结晶相. X射线衍射证实样品呈尖晶石结构. 利用场发射扫描电子显微镜研究结构形态和纳米颗粒的大小. 饱和磁化强度在100和300 K时,随着钯含量增加达5%降低,但加入10%Pd时磁化强度突然上升.     

Electronic absorption spectra of amino substituted anthraquinones and their interpretation using the ZINDO/S and AM1 methods

Electronic absorption spectra of 1,2-diamino-9,10-anthraquinone (12DAAQ), 1,4-diamino-9,10-anthraquinone (14DAAQ), 1,5-diamino-9,10-anthraquinone (15DAAQ), and 2,6-diamino-9,10-anthraquinone (26DAAQ) are investigated. Molecular geometries of the amino anthraquinones in the ground state are optimized using the semiempirical ZINDO/1 and AM1 methods without imposing any symmetry constraints. The ground state geometries of all the molecular systems are found to be planar. For interpretation of the spectra, ZINDO/S-CI and AM1-CI calculations employing singly excited configuration using the completely optimized geometry are carried out. Such calculations on the electronic spectra of amino anthraquinones are carried out for the first time. On the basis of these calculations, the assignment of the spectra are successfully made.     

Effect of UV irradiation on the structural,optical and electrical properties of platinum

Investigations are performed on thermal, optical and electrical response of UV laser-irradiated platinum (Pt). 4N pure, annealed and fine polished samples are exposed to the KrF Excimer laser (248 nm, 20 ns, 50 mJ) under vacuum ～10^?6 torr at different laser fluences (0.5–2.5 J/cm²). Space-resolved plasma plume dynamics is studied by analyzing the captured plume images with the help of a computer controlled image-grabbing system. The irradiated targets are characterized for surface morphology, structural, optical and electrical investigations using the diagnostics; scanning electron microscopy, X-ray diffraction, rotating compensator auto-aligned ellipsometer and four-point probe, respectively. The value of maximum intensity emitted by Pt plasma plume is 250 grey scales. Surfaces of the target metals are modified by craters, moltens and redeposited material. Laser-induced periodic surface structures are produced at low laser fluence. Irradiation of Pt causes changes in diffracted X-rays intensity and grain sizes, dislocation in line densities and strain in the target materials. Considerable changes occur in optical parameters as well. A decrease in electrical conductivity of the irradiated targets also takes place in an exponential way with the change in laser fluence.     

Small polaron hopping conduction mechanism in Ni-doped LaFeO3

The electrical transport properties of LaFe_{1? x} Ni _x O₃ (0.1 ≤ x ≤ 0.6) bulk samples were investigated over a wide temperature range, i.e. 9–300 K. Powder x-ray diffraction patterns at room temperature showed that all samples were formed in a single phase. However, a structural transformation was observed from orthorhombic (Pnma) to rhombohedral crystal symmetry at x > 0.5 in Ni-doped samples, which is supported by the electrical transport analysis. Temperature-dependent resistivity data were fitted using Mott's variable-range hopping model for a limited range of temperatures to calculate the hopping distance and the density of states at Fermi level. It was found that all parameters vary systematically with an increase in Ni concentration. Moreover, the resistivity data were also fitted using the small polaron hopping (SPH) model. The non-adiabatic SPH conduction mechanism is followed up to 50% Ni concentration, whereas an adiabatic hopping conduction mechanism is active above it. Such a change in the conduction mechanism is accompanied by subtle electronically induced structural changes involving Fe³⁺–O–Fe³⁺ and Fe³⁺–O–Ni³⁺ bond angles and bond lengths. Thus, we suggest that the transport properties can be explained according to the additional delocalization of charge carriers induced by Ni doping.     

Transient characteristics of the InGaP–GaAs–InGaAs–GaAs transistor laser

Transient characteristics of the InGaP–GaAs–InGaAs (quantum well)-GaAs transistor laser are studied. Rate equations are numerically solved to obtain the response of current density and photon density. Expression of resonance frequency $f_{r}$ is obtained by solving the rate equations analytically. It has been found that the $f_{r}$ increases with decreasing spontaneous carrier lifetime and with increasing value of the bias current density.