The role of CdTe solar cell processing on the defect chemistry that limits open circuit voltage (VOC) is addressed in the thermochemical processing regimes commonly encountered in present-generation CdTe devices. The highest VOC is 0.91 V for a bulk CdTe crystal with ITO which is only marginally higher than VOC = 0.86 V obtained for polycrystalline CdTe films with CdS. Both fall ∼0.4 V short of the VOC expected for CdTe, having band gap EG = 1.5 eV. The present >16% efficient superstrate CdTe cell uses a process based on high-temperature, T > 500°C, CdTe growth on CdS, coupled with optimized methods for incorporating oxygen, sulfur, copper, and chloride species in the CdTe film. Pushing cell conversion efficiencies beyond 20% will require increasing VOC beyond 1V. However the present pathway of processing optimization will likely yield VOC and efficiency converging on 0.9 V and <20%, respectively.

The present work deals with the comparative investigation of Si-ncs embedded in SiO2 and Al2O3 dielectrics grown by RF magnetron sputtering on fused quarts substrate. The effect of post-deposition processing on the evolution of microstructure of the films and their optic and luminescent properties was investigated. It was observed that photoluminescence (PL) spectra of Six(SiO2)1-x films showed one PL band, which peak position shifts from 860 nm to 700 nm when the x decreases from 0.7 to 0.3. It is due to exciton recombination in Si-ncs. For Six(Al2O3)1-x films, several PL bands peaked at about 570-600 nm and 700-750 nm and near-infrared tail or band peaked at about 800 nm were found. Two first PL bands were ascribed to different oxygen-deficient defects of oxide host, whereas near-infrared PL component is due to exciton recombination in Si-ncs. The comparison of both types of the samples showed that the main radiative recombination channel in Six(SiO2)1-x films is exciton recombination in Si-ncs, while in Six(Al2O3)1-x films the recombination via defects prevails due to higher amount of interface defects in the Six(Al2O3)1-x caused by stresses.

Deformation behavior of the directionally-solidified MoSi2/Mo5Si3 eutectic composites has been investigated as a function of the average thickness of MoSi2 phase over a temperature range from 900 to 1500°C. The average thickness of both MoSi2 and Mo5Si3 phases in the directionally-solidified ingots with script-lamellar morphologies grown by optical floating zone method decreases with increasing the growth rate. Plastic deformation was observed above 1000°C for all the DS ingots grown at different growth rates when the loading axis is parallel to [1¯10]MoSi2 close to the growth direction. Yield stress decreases monotonically with increasing temperature. Yield stress at 1400°C increases drastically with decreasing the average thickness of MoSi2 phase.

Treatment of [Li+@C60](PF6 –) with 30% fuming sulfuric acid and subsequent hydrolysis gave hydroxylated derivative Li+@C60O–(OH)7. Its structure was deduced by IR, NMR, MALDI-TOF/FAB MS, and elemental analysis. Notably, the reaction of [Li+@C60](PF6 –) was site-selective, giving a single major isomer (ca. 70%) with two minor isomers, in marked contrast to the case of empty C60. Furthermore, the results clearly indicate that the internal Li cation was strongly shielded by the surface dipolar hydroxyl groups, and thus it appears that the properties of endohedral fullerenes can be controlled by the external modification of the fullerene cage. Whereas Li+@C60 is relatively insoluble, Li+@C60O–(OH)7 was found to be highly soluble in polar solvents such as DMSO and DMF. The increased solubility is especially desirable for biological/medicinal assays and applications in such research fields.

Zinc oxide (ZnO) thin film deposited onto indium tin oxide (ITO) coated Corning glass substrates using pulsed laser deposition (PLD) technique has been used as a matrix for realization of an efficient urea biosensor after immobilization of urease (Urs) enzyme onto the surface of ZnO. The bioelectrode (Urs/ZnO/ITO/glass) is found to be exhibiting an enhanced sensitivity of 22μΑmΜ−1cm−2 towards urea over a wide detection range of 5-200 mg/dl. The relatively low value of Michaelis menten constant (Km= 0.94mM) indicates high affinity of the immobilized urease towards the analyte (urea). The prepared biosensor retains 90% of its activity for more than 10 weeks. The observed enhanced response characteristics of bioelectrode are attributed to the growth of the matrix (highly c-axis oriented ZnO thin film) with desired surface morphology and high electron communication feature. The results confirm the promising application of PLD grown ZnO thin film as an efficient matrix for urea detection.

Bio-conjugated CdSe/ZnS core/shell quantum dots (QDs) attract essential scientific interest due to their possible nano-medicine applications, including selective highlighting of affected tissues and targeted drug delivery to the certain type of cells. The paper is focused on the theoretical description of the blue shift observed in the luminescence spectra of CdSe/ZnS QDs upon their bio-conjugation with the anti-interleukin-10 antibodies. We propose a model that describes the ground state of the exciton confined in a quantum dot and explaining the bio-conjugation phenomenon by the change of the effective confinement volume.

Large-area fast lithium ion conducting ceramic thin freestanding sheets was successfully prepared using a sheet forming technique. This ceramic sheet contains the crystalline phase of Li1+x+yAlxTi2-xSiyP3-yO12 with the NASICON type structure. The ceramic sheet showed maximum overall conductivity over 10−3 S cm−1 at room temperature. And, the developed thin ceramic sheet has sufficient flexibility against bending stress. Because a thin large-area ceramic electrolyte sheet was prepared using less energy compared with a conventional glass casting method, it is suitable for practical use.

An important property of thin film silicon and related materials is the microstructure which may involve the presence of interconnected and isolated voids. We report on effusion measurements of implanted helium (He) to detect such voids. Several series of hydrogenated and unhydrogenated amorphous silicon films prepared by the methods of plasma deposition, hot wire deposition and vacuum evaporation were investigated. The results show common features like a He effusion peak at low temperatures attributed to He out-diffusion through a compact material or through interconnected voids, and a He effusion peak at high temperatures attributed to He trapped in isolated voids. While undoped plasma-grown device-grade hydrogenated amorphous silicon (a-Si:H) films show a rather low concentration of such isolated voids, its concentration can be rather high in doped a-Si:H, in unhydrogenated evaporated material and others.

Nonvolatile unipolar resistive switching properties of the amorphous LaGdO3 thin films deposited by pulsed laser deposition have been studied. Reliable and repeatable switching of the resistance of LaGdO3 film was obtained between low and high resistance states with nearly constant resistance ratio ∼ 106 and non-overlapping switching voltages in the range of ∼0.6-0.75 V and 2.5-4 V respectively. The switching between low and high resistance states was attributed to the formation and rupture of conductive filaments using temperature dependent resistance measurements. The current conduction mechanisms of the LaGdO3 film in low and high resistance states were found to follow the Ohmic behavior and Poole-Frenkel emission respectively. The resistance of low and high resistance states of the film remained nearly constant for up to ∼ 104 seconds indicating good retention. The observed resistive switching characteristics of LaGdO3 thin films are promising for futuristic nonvolatile memories.

Triboemission comprises the emission of low energy electrons and photons, the eventual formation of micro-triboplasmas, and the possible charge-initiated tribochemical reactions on the surfaces under contact. Electron triboemission is often seen as a case of electron exoemission, but such low-energy output may be just a fraction of the total electronic excitation on the surface, the majority of which may proceed as internal currents. The dynamics of these related surface phenomena have been investigated by different techniques, which are discussed in this work; in particular, the authors have obtained extensive data indicating that electrons and photons are produced from mechanical surface work, particularly from surface oxides and semiconductors under contact sliding in vacuum. This paper also discusses the existing body of work on triboemission, and the possible use of the developed measurement techniques as novel probes for surface processes.

Porous, nanostructured silver samples were produced using a direct-write method where a nanoparticle aerosol consisting of particles with a mean size of approximately 5 nm were accelerated to speeds of approximately 1000 m/sec and impacted onto a translating substrate [1]. The impacting particles have sufficient energy to stick to the substrate, allowing patterned thick films to be directly written from the aerosol without a mask. Unlike other low temperature processing routes for achieving patterned films, no organics are added that can interfere with postdeposition processing. Typical films are 5- 100 μm thick, up to several centimeters long, and have an as-deposited relative densities as high as 70% of bulk Ag. Compression tests were carried out in steps at room temperature and at 150°C under constant displacement rates. Local strain and densification were measured by optical profilometry between each compression step. The results can be used as a starting point to better understand the mechanisms that govern plasticity, creep, and sintering in nanostructured, porous silver at low processing temperatures.

We use new neutron scattering instrumentation to follow in a single quantitative time-resolving experiment, the three key scales of structural development which accompany the crystallisation of synthetic polymers. These length scales span 3 orders of magnitude of the scattering vector. The study of polymer crystallisation dates back to the pioneering experiments of Keller and others who discovered the chain-folded nature of the thin lamellae crystals which are normally found in synthetic polymers. The inherent connectivity of polymers makes their crystallisation a multiscale transformation. Much understanding has developed over the intervening fifty years but the process has remained something of a mystery. There are three key length scales. The chain folded lamellar thickness is ∼ 10nm, the crystal unit cell is ∼ 1nm and the detail of the chain conformation is ∼ 0.1nm. In previous work these length scales have been addressed using different instrumention or were coupled using compromised geometries. More recently researchers have attempted to exploit coupled time-resolved small-angle and wide-angle x-ray experiments. These turned out to be challenging experiments much related to the challenge of placing the scattering intensity on an absolute scale. However, they did stimulate the possibility of new phenomena in the very early stages of crystallisation. Although there is now considerable doubt on such experiments, they drew attention to the basic question as to the process of crystallisation in long chain molecules. We have used NIMROD on the second target station at ISIS to follow all three length scales in a time-resolving manner for poly(e-caprolactone). The technique can provide a single set of data from 0.01 to 100Å-1 on the same vertical scale. We present the results using a multiple scale model of the crystallisation process in polymers to analyse the results.

Hybrid nano/micro particles were investigated for their possibility to re-structure within local pH alterations, release certain active substance and further contribute to increased steel corrosion resistance. Two aspects with regard to corrosion control and self-healing in cement-based materials are discussed: the first aspect deals with the electrochemical performance of low carbon steel electrodes (St37) in model alkaline solutions (cement extract) in the presence of 4.9.10-4 g/l hybrid particles i.e. cement extract, containing PDADMAC (poly (diallyl, dimethyl ammonium chloride) / PAA (Poly (acrylic acid)/ PDADMAC over a CaO core. The second aspect refers to the performance of reinforcing steel (FeB500 HKN) in mortar specimens, containing hybrid particles in the mixing water in concentration of 3.6×10-4 wt. % per mortar weight. The main objective was to determine if these hybrids will lead to increased corrosion resistance of the steel surface layers, generally formed in the hereby investigated environmental medium (both liquid i.e. cement extract and solid i.e. mortar). Further, it was expected that when chlorides are involved, as corrosion accelerating factor, the presence of hybrid particles will delay corrosion initiation and will therefore lead to increased corrosion resistance. The results denote for indeed superior corrosion performance of steel in chloride-free and chloride containing medium, when hybrid particles are involved. The responsible mechanisms are related to increased barrier effects of the formed layer and self-repair upon morphological alterations of the hybrid particles, “nucleation sites effects” and/or Ca-core “release” on locally active (anodic) areas on the steel surface.

The goal of this work is to increase the efficiency of conventional solar cells by incorporating quantum dot (QD) nanoparticles in the absorption mechanism. The strategy is to have the QDs absorb UV and fluoresce photons in the visible region that are more readily absorbed by the cells. The outcome is that the cells have more visible photons to absorb and have increased power output. The QDs, having a CdSe core and a ZnS shell, were applied to the solar cells as follows: (1) The QDs were first synthesized in a solution. (2) They were then removed from the solution and dried. (3) The dried QDs are then deposited into polydimethylsiloxane (PDMS) and the PDMS/QD composite is allowed to cure. (4) The cured sample is applied to a silicon solar panel. The panel with the PDMS/QD application outputs 2.5% more power than the one without, under identical AM1.5 illumination using QDs that fluoresce in the orange region. This work demonstrates the feasibility of incorporating QDs to increase the efficiency of conventional solar cells. Because the cells absorb better in the red region, future effort will be to use QDs that fluoresce in that region to further boost cell output.

Structure-related ionization energy (IE) of vacuum-deposited titanyl-phthalocyanine (OTiPc) thin films was investigated by using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray diffractometry. Distinct molecular orientations (i.e. lying-flat and standing-up orientation) in different polymorphous (i.e. monoclinic β-phase and triclinic α-phase) were observed on a surface of polycrystalline (poly-) Au and octadecyltrichlorosilane-self assembled monolayer (OTS-SAM). For the two structures IE of the highest occupied molecular orbital (HOMO) of OTiPc thin films altered significantly by 0.55 eV. The different IE was attributed to surface dipole potential and strong intermolecular interaction.

In this work we study the influence of supercell scaling on magnetic properties in Ni-Mn-X-Z alloys by means of ab initio calculations with the help of Quantum Espresso PWSCF package and the spin-polarized relativistic Korringa-Kohn-Rostoker (SPR-KKR) code based on DFT approximation. It is shown that the supercell calculations for the equilibrium lattice parameter are coincided with the calculations for simple primitive lattice. The exchange parameters for Ni-Mn-X alloys obtained from supercell calculations are large than calculated for simple primitive lattice.

Optical emission spectroscopy (OES) and Langmuir Probe were used to characterize RF and VHF plasma properties under conditions leading to nanocrystalline silicon film deposition. Films deposited by RF plasma at low pressure (3 Torr), even with high crystalline volume fraction, show weak X-ray diffraction signals, suggesting small grain size, while RF films at higher pressure (8 Torr) and VHF films at both high and low pressure have larger grain sizes. The preferential growth orientation is controlled by the H2/SiH4 ratio with RF plasma, while the film deposited by VHF shows primarily (220) orientation independent of H-dilution ratio. Langmuir Probe measurements indicate that the high energy electron population is reduced by increasing pressure from 3 Torr to 8 Torr in RF plasma. Compared with RF plasma, the VHF plasma shows higher electron density and sheath potential, but lower average electron energy, which may be responsible for the larger grain size and crystal orientation. The growth rate and crystalline volume fraction of the film is correlated with OES intensity ratio of SiH* and Hα/SiH* for both RF and VHF plasmas.

Thin film deposition process and integrated scribing technologies are key to forming large area Cadmium Telluride (CdTe) modules. In this paper, baseline Cd1-xZnxS/CdTe solar cells were deposited by atmospheric-pressure metal organic chemical vapor deposition (AP-MOCVD) onto commercially available ITO coated boro-aluminosilicate glass substrates. Thermally evaporated gold contacts were compared with a screen printed stack of carbon/silver back contacts in order to move towards large area modules. P2 laser scribing parameters have been reported along with a comparison of mechanical and laser scribing process for the scribe lines, using a UV Nd:YAG laser at 355 nm and 532 nm fiber laser.

The n-type hydrogenated microcrystalline silicon oxide (μc-SiOX:H(n)) films with different stoichiometry have been successfully prepared by varying the CO2-to-SiH4 flow ratio in the PECVD system. By using the μc-SiOX:H(n) as a replacement for μc-Si:H(n) and ITO, the conversion efficiency of μc-Si:H single-junction and a-Si:H/μc-Si:H tandem cells were improved to 6.35% and 10.15%, respectively. The major improvement of the short circuit current density (JSC) and these cell efficiencies were originated from the increased optical absorption, which was confirmed by the quantum efficiency measurement showing increased response in the long-wavelength region. Moreover, the all PECVD process except the metal contact simplified the fabrication and might benefit the industrial production.

We propose an implementation of the PCD technique to minority carrier effective lifetime assessment in crystalline silicon at 77K. We focus here on (n)-type, FZ, polished wafers passivated by a-Si:H deposited by PECVD at 200°C. The samples were immersed into liquid N2 contained in a beaker placed on a Sinton lifetime tester. Prior to be converted into lifetimes, data were corrected for the height shift induced by the beaker. One issue lied in obtaining the sum of carrier mobilities at 77K. From dark conductance measurements performed on the lifetime tester, we extracted an electron mobility of 1.1x104 cm².V-1.s-1 at 77K, the doping density being independently calculated in order to account for the freezing effect of dopants. This way, we could obtain lifetime curves with respect to the carrier density. Effective lifetimes obtained at 77K proved to be significantly lower than at RT and not to depend upon the doping of the a-Si:H layers. We were also able to experimentally verify the expected rise in the implied Voc, which, on symmetrically passivated wafers, went up from 0.72V at RT to 1.04V at 77K under 1 sun equivalent illumination.