Despite organic solar cells have recently shown remarkable high power conversion efficiencies approaching 10%, further improvements are required to provide a low-cost alternative to inorganic photovoltaics. Optical losses related to insufficient light trapping and parasitic absorption of the contact layers limit drastically the photocurrent delivered by the cells. Textured surfaces, such as V-grooves (2D) and pyramids (3D), can provide better light coupling into the conformally deposited solar cells. In this work, we analyze the enhancement in light absorption in textured solar cells based on copper phtalocyanine (CuPc) and fullerene (C60) on the micro- and submicroscale. The analysis is carried out with the aid of the finite element method in 2D and 3D, taking into account interference as well as reflection and refraction of the incident AM1.5G spectrum. The results show that both type of structured cells perform better than planar cells reaching up to 23% improvement in maximum photocurrent for normal incidence. We also explore the lateral inhomogeneities of the generation rate within the active layers and their potential effect on the exciton collection efficiency.

Strong short electric field pulses are used to generate broadband terahertz radiation. Understanding the transport properties under such conditions is very important for the understanding of numerous terahertz photonic and electronic devices. In this paper, we report on transport simulations of the electrons within bulk wurtzite zinc oxide for pulsed high electric fields, with pulse durations of up to 400 fs. We focus on how key electron transport characteristics, namely the drift velocity and the corresponding average energy, vary with time since the onset of the pulse. For sufficiently high-field strength selections, we find that both of these parameters exhibit peaks. In addition, an electron drift velocity undershoot is observed following this peak. A contrast with the case of gallium nitride is considered; undershoot is not observed for the case of this material. Reasons for these differences in behavior are suggested.

Carbon nanofibers (CNFs) have been thoroughly investigated as potential anode materials in Li-ion battery owing to their exceptional properties such as the higher surface area to mass ratio, electrical conductivity and mechanical toughness. However, one of the major limitations of nano carbon materials is lower mass loading density. To address this issue, we have developed a novel anode system composed of CNFs directly grown on 3D Cu mesh current collector (hereafter mentioned as 3D CNFs) using a thermal catalytic chemical vapor deposition (CVD) method. Compared to CNF-based anodes on 2D Cu current collector, active The active material loading amount of the 3D CNFs has been found to be 400 % higher while comparing with 2D CNF. Owing to an increase of the active surface area, 3D CNFs demonstrated enhanced electrochemical performance of Li-ion battery in terms of charge capacity (50% improvement), rate capability and cycling life. Interfacial contact between the CNFs and Cu could play a crucial role in promoting the electrochemical properties. The intermediate TiC thin layer, formed at high temperature 750°C, could function as an efficient electric conducting pathway and a strong bonding bridge between the CNFs and Cu. In order to improve the pristine 3D CNF redox reactions, the amorphous Si (a-Si)/3D CNF has been sputter deposited to produce Si wrapped 3D CNF hybrid anode material. It has been found that the electrochemical properties of the a-Si/3D CNF yields superior specific capacity (Cdis 549 mAhg-1, LiC4.1) and cycling stability than that of pristine 3D CNF (461 mAhg-1, LiC4.8).

At the present time, no material is known that is completely inert to chemical or biochemical action and immune to weathering damage. Concrete is no exception, but, under what might be considered normal exposure conditions, it has a very long life. Concrete made by the Romans from natural cement is in excellent condition after more than 2000 years of service. The controversies generated by contradictory expert testimonies in several lawsuits involving sulfate attack on concrete, and by the large numbers of recently published papers containing data on the subject, have caused considerable anxiety about sulfate attack mechanisms and the service life of concrete structures. Furthermore, frequently the physical attack by salt crystallization is being confused with the classical sulfate attack, which involves the chemical interaction between sulfate ions from an external source and the constituents of cement paste. In addition, there is also an internal sulfate attack –a chemical attack in which the source of sulfate ions resides in the concrete aggregates or cement–. Additionally, modern concrete as been affected by the products of microorganism metabolism, in particular sulfuric acid, this damage done to hardened concrete is known as concrete biodeterioration and also known as microbiologically induced corrosion of concrete (MICC). Being perhaps this biodeterioration the most important cause of concrete decay and perhaps the true explanation of sulfate attack on concrete. Some of the controversies about sulfate attack are addressed in this article, we have studied the case applying simple considerations concerning concrete composition and flouting at the same time some of the stricter observed paradigms in the cement and concrete industry. It is concluded that a holistic approach is necessary to separate the real causes of sulfate attack on concrete from the imaginary ones.

The electroluminescent characteristics of blue organic light-emitting diodes(BOLEDs) were fabricated with single emitting layer using host-dopant system and doped charge carrier transport layers. The structure of the high efficiency BOLED device was; NPB(600Å)/NPB:BCzVBi-7%(100Å)/ADN:BCzVBi-7%(300Å)/BAlq:BCzVBi-7%(100Å)/BAlq(200Å)/Liq(20Å)/Al(1200Å) to optimize probability of exciton generation by doping BCzVBi in emitting layer and hole/electron transport layers(HTL/ETL) as well. Luminance and luminous efficiency of BOLED doped BCzVBi in EML and HTL/ETL improved from 10090 cd/m2 at 9.5V and 6.44 cd/A at 4.0V to 13190 cd/m2 at 9.5V and 7.64 cd/A at 4.0V about 30% and 18%, respectively, with CIE coordinates of (0.14, 0.17) comparing to BOLED doped BCzVBi in EML only

Carbon nanotubes patterns of micron-level resolution have been achieved using inkjet printing of DNA and SDS assisted CNT dispersions. DNA/CNT film has a significantly higher resistance compared to SDS/CNT film. Taking advantage of the porous nature of printed SDS/CNT film after SDS removal, indium can be electroplated to fill the CNT network and form a CNT/In composite. The CNT/In composite was used as interconnect material. Reworkability and RF performance of In-plated CNT bump structures are studied and the results are presented.

Manganese oxide based nanoparticles were synthesized by sol-gel process. Methanol, ethanol, and propanol were used as alternative solvent during sol-gel process with manganese acetate as precursor for the preparation of pristine manganese oxide. Hybrid MnOx modified by additions of carbon nanotubes was further prepared. Smallest particle size was observed for manganese oxide prepared from propanol, with diameters range from 16 nm to 50nm. XRD results showed that the as prepared manganese oxide based samples at calcination temperature of 300°C and above were composed of Mn2O3 as dominant phase, with Mn3O4 as minor phase. Specific capacitance measured from two electrode systems of manganese oxide prepared from methanol, ethanol, and propanol at scan rate of 10 mV/s were 88.3, 66.0, 104.8 F/g and the result for the hybrid sample was 140.5 F/g. The highest capacitance of the MnOx revealed a specific capacitance of 231.4 F/g when a 1:1 mixture of propanaol and methanol was employed as the solvent for the sol preparation. Results from electrochemical impedance spectroscopy (EIS) also showed superior electrochemical properties of the hybrid sample over pristine manganese oxide samples.

Record-brightness infrared LEDs based on colloidal quantum-dots have been achieved through control of the spacing between adjacent quantum-dots. By tuning the size of quantum-dots, the emission wavelengths can be tuned between 900nm and 1650nm.

Cu(InGa)Se2 solar cells modeling is challenging due to their complex electronic structure, to the presence of interface states between layer and grains and to the microcrystalline structure of the absorber. Here we present a ISE-TCAD based realistic absorber 3D model, with the specific objective to take into account, among several effects, these challenging aspects. The CdS/Cu(InGa)Se2 solar cell is modeled as an array of columnar microcells, connected in parallel, mimicking the polycrystalline nature of the absorber. The model optical and electrical parameters are optimized based on a review of available experimental material characterization and realization results. Simulation outcomes are compared with experimental data in order to validate the model.

In this work we present a detailed theoretical investigation of the thermal conductivities of n-type 0.1 wt.% CuBr doped 85% Bi2Te3 - 15% Bi2Se3 and p-type 3 wt% Te doped 20% Bi2Te3 - %80 Sb2Te3 single crystals. The thermal conductivity contributions arising from carriers, electron-hole pairs and phonons are computed rigorously in the temperature range $300\,{\rm{K}}\, \le \,T\, \le \,500\,{\rm{K}}$ . In agreement with available experimental measurements we theoretically find that the lowest total thermal conductivity is 3.15 W K−1 m−1 at 380 K for the n-type alloy and 1.145 W K−1 m−1 at 400 K for the p-type alloy. Stronger mass-defect scattering is found to be responsible for the lower thermal conductivity of the p-type alloy throughout the temperature range of the study.

Atomistic lattice-gas models for thermodynamically and kinetically directed assembly are applied to Ru nanocluster formation on a monolayer of graphene supported on Ru(0001) at 309 K. Nanocluster density, mean size, height distribution, and spatial ordering are analyzed by kinetic Monte Carlo simulations. Both models can reproduce the experimental data, but additional density functional theory analysis favors the former.

Highly transparent and conducting Fluorine doped zinc oxide thin films were deposited using spray pyrolysis method on glass substrates held at 450 °C. The X-ray diffraction study revealed that as the dopant concentration increases in ZnO films, the intensity of the preferential orientation of (002) reflection decreased and (101) was found to increase up to 5 at. % F. The crystallite size was varied from 40 to 50 nm with dopant concentration. The optical band gap of the un-doped films was 3.30 eV and it increased to 3.34 eV for 3 at. % F. The refractive index of the films was increased from 2.05 to 2.18 with the increase of dopant concentration from 0 to 5 at. %. The scanning electron microscopy results depicted that the microstructure of ZnO: F films highly influenced by the fluorine doping. After annealing the films in hydrogen atmosphere, the resistivity of the films decreased as increase the dopant concentration and it is 4×10−3 Ω cm for 3at. % F beyond which it increased. The mobility of the charge carriers was 14 cm2/ V sec and the carrier concentration was 7.8×1019 cm3 obtained for the films doped with 3 at. % of fluorine concentration in the starting solution.

Carbon-based nanostructures have been the center of intense research and development for more than two decades now. Of these materials, graphene, a two-dimensional (2D) layered material system, has had a significant impact on science and technology in recent years after it was experimentally isolated in single layers in 2004. The recent emergence of other classes of 2D layered systems beyond graphene has added yet more exciting and new dimensions for research and exploration given their diverse and rich spectrum of properties. For example, h-BN a layered material closest in structure to graphene, is an insulator, while NbSe, a transition metal dichalcogenide is metallic and monolayers of other transition metal di-chalcogenides such as MoS2 are direct band-gap semiconductors. The rich variety of properties that 2D layered material systems offer can potentially be engineered on-demand, and creates exciting prospects for their device and technological applications ranging from electronics, sensing, photonics, energy harvesting and flexible electronics in the near future.

Papers in the Appendix were published in electronic format as Volume 1534

Semiconductor heterostructures as quantum dots demonstrate discrete atom-like energy level structure based on several hundred of electron confinement states. In the case of double QD (DQD) or double QR (DQR), there is a single electron spectrum composed of a set of quasi-doublets. We study these specific spectrum properties with their relation to the electron tunneling in DQD (DCQR) when the wave function of electron localized initially in one of the double quantum object is spread into whole system. The double InAs/GaAs quantum dots are considered within the effective approach. Tunneling in DQD is studied in connection with change of inter-dot distance and QD geometry. There are two types of such tunneling in DQD. The first is related to tunneling in the system of two identical QDs; the second one occurs in the system of non-identical QDs. The tunneling in the DQR is a tunneling in the system with non-identical quantum objects. The quasi-doublets of the DQD spectrum play an important role in the tunneling. We study effect of violation of symmetry of DQD geometry on the tunneling and show that the violation of symmetry makes difficulties for such tunneling.

The traditional CdCl2 passivation of CdTe is expanded by adding other chlorides such as MgCl2, NaCl, and MnCl2 into the process through a two-step passivation procedure that combines closed space sublimation step with a vapor process. This allows the possibility of forming a highly doped field at the back of the device that could act as an electron reflector that could boost device performance by directing electrons back into the absorber layer and increasing the voltage while limiting recombination at the back of the device. The effects the two-step passivation process on device performance are characterized by current-voltage measurements, and by electroluminescence and laser-beam induced current images to show the degree of device uniformity. Additionally, capacitance voltage measurements are used to study doping density, depletion width, and possible formation of a field at the back of the device.

The present work investigates the UV stability of the dye-sensitized solar cell (DSC) by parametrical investigation of the material influence on UV stability. UV illumination has been observed to cause degradation by slow photocatalysis in the DSC. Photooxidized impurities represent an unwanted side reaction with the redox pair of the electrolyte as the released electron will deplete the triiodide concentration. A study on the DSC cell was carried out with intermediate electrical characterization by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) to map the influence of UV illumination as a function of the H2O concentration in the electrolyte, the plate distance and the triiodide concentration. The results show that the H2O content has a detrimental influence on the DSC stability during UV illumination. A higher concentration of triiodide can buffer the reaction with impurities, so that a longer-term stability is achieved. A recovery of triiodide in UV aged cells with either no remaining triiodide or with such a low concentration that the cell current has been diffusionlimited, was seen during CV to -0.75 V under illumination. The reappearance of triiodide was accompanied with a production of hydrogen bubbles, which was related to the H2O content in the electrolyte and the exposure to UV. Our approach can be used to test the purity and the UV stability of various electrolytes.

A study on light absorption enhancement of an InAs quantum dots embedded into InxGa1-xAs quantum well with GaAs as a barrier solar cells was carried out. Solar cell devices were fabricated from different structures, which were grown by using molecular beam epitaxy, with the In mole fraction (x) varied between 0 – 25 %. Poly-L-Lysine ligands and ZnO sol-gel was used to modify the surface of the solar cells and act as anti-reflection coatings. The anti-reflection characteristic of the ligands and the sol-gel were investigated by measuring the solar cell characteristics before and after the solar cells surface modifications. The current-voltage characteristics were measured of the fabricated solar cells before and after Poly-L-Lysine and ZnO coatings. A significant enhancement on the order of 40 % of the solar cells performance was observed. This type of enhancement was observed in the power conversion efficiency, spectral response measurements, and external quantum efficiency.