Electrical Characteristics Analysis of Bonded Cells for Shingled Modules.

A shingled module fabricated using electrically conductive adhesive (ECA) can increase the light-receiving area and provide greater power than a conventional module fabricated using solder-coated copper ribbons. However, several issues such as damage from laser cutting and poor contact by the conductive paste may arise. In this study, a 15.675 × 3.1 cm² c-Si cut cell was fabricated using a nanosecond green laser, and cell bonding was performed using ECA to fabricate shingled modules. If the laser process was performed with high speed and low power, there was insufficient depth for cut cell fabrication. This was because the laser only had a thermal effect on the surface. The cell was processed to a depth of approximately 46 µm by the laser, and it could be seen that the laser cutting proceeded smoothly when the laser process affected more than 25% of the wafer thickness. The cut cell was bonded by ECA, and the process conditions were changed. The highest efficiency of 20.27% was obtained for a cell bonded under the conditions of a curing time of 60 s and curing temperature of 150°C. As a result, the efficiency of the bonded cell was increased by approximately 2.67% compared to the efficiency of the conventional cut cell. This was because the shadow loss due to the busbar was reduced, increasing the active area of the module by eliminating the busbar from the illuminated area.

Characteristics of TAA-ZnS Buffer Layer by Addition of Sodium Citrate for CIGS Thin Film Solar Cell.

Zinc Sulfide (ZnS) is an environmentally friendly material with a wide bandgap (Eg = 3.7 eV) comparable to that of cadmium sulfide (CdS) (2.4 eV), which is conventionally used as buffer layer in Cu(In,Ga)Se2 (CIGS) thin film solar cells. Conventional ZnS buffer layers are manufactured using thiourea, and, these layers possess a disadvantage in that their deposition rate is lower than that of CdS buffer layers. In this paper, thioacetamide (TAA) was used as a sulfur precursor instead of thiourea to increase the deposition rate. However, the ZnS thin films deposited with TAA exhibited a higher roughness than the ZnS thin films deposited with thiourea. Sodium citrate was therefore added to increase the uniformity and decrease the roughness of the former ZnS thin films. When sodium citrate was used, the thin films demonstrated a high transmittance via the controlled generation of particles. In the case of TAA-ZnS thin films doped with a sodium citrate concentration of 0.04 M, the granules on the surface disappeared and these thin films were denser than the TAA-ZnS thin films deposited with a lower sodium citrate concentration. It is considered that the rate of the ion-by-ion reaction increased due to the addition of sodium citrate, thereby resulting in a uniform thin film. Consequently, TAA-ZnS thin films with thicknesses of approximately 40 nm and high transmittances of 83% were obtained when a sodium citrate concentration of 0.04 M was used.

Piezophototronic Effect Modulated Multilevel Current Amplification from Highly Transparent and Flexible Device Based on Zinc Oxide Thin Film.

In this work, a strain modulated highly transparent and flexible ZnO/Ag-nanowires/polyethylene terephthalate optoelectronic device is developed. By utilizing the applied external strain-induced piezophototronic effects of a ZnO thin film, a UV-generated photocurrent is tuned in a wide range starting from 0.01 to 85.07 µA and it is presented in a comprehensive map. Particularly, the performance of the device is effectively enhanced 7733 times by compressive strain, as compared to its dark current in a strain-free state. The observed results are explained quantitatively based on the modulation of oxygen desorption/absorption on the ZnO surface under the influence of applied strains. The presented simple optoelectronic device can be easily integrated into existing planar structures, with potential applications in highly transparent smart windows, wearable electronics, smartphones, security communication, and so on.

Characterization of ZnS Thin Films Grown Using Chemical Bath Deposition with Three Different Complexing Agents.

Cadmium sulfide buffer layer was replaced with zinc sulfide thin film owing to toxicity. ZnS thin films were fabricated using chemical bath deposition. The inhibition of Zn(OH)2 and high uniformity are important factors for the deposition of ZnS. The characteristics of ZnS thin films were analyzed by adding ethylenediamine tetra-acetate acid (EDTA) and hexamethylene tetramine (HMTA). The morphological characteristics of the ZnS buffer layer are closely related to the use of a complexing agent which controls the concentration of Zn2+ ions and Zn(OH)2 in the deposition process. The addition of the complexing agent EDTA accelerated the cluster-cluster method but it exhibited lower uniformity and greater cracking phenomenon. HMTA can be effectively applied to increase the amount of Zn2+ ions forming ZnS. It can be easily found as Zn2 HMTA at high temperatures. The results of the experiment with the addition of HMTA revealed that the surface of the thin film did not change with the increase in the concentration of HMTA, but the thickness of the thin film increased gradually. HMTA promoted the ion-ion method to grow the thin film uniformly, but the speed was slow. Moreover, an experiment by using mixed EDTA and HMTA as the complexing agent was performed. The best ZnS thin film with a transmittance of 83% and a denser surface was prepared using HMTA complexing agent.

Influence of Post-Heat Treatment of ZnO:Al Transparent Electrode for Copper Indium Gallium Selenide Thin Film Solar Cell.

Copper indium gallium selenide (CIGS) thin film solar cells have been regarded as a candidate for energy conversion devices owing to their high absorption coefficient, high temperature stability, and low cost. ZnO:Al thin film is commonly used in CIGS solar cells as a window layer. In this study, ZnO:Al films were deposited on glass under various post-heat temperature using RF sputtering to observe the characteristics of ZnO:Al films such as Hall mobility, carrier concentration, and resistivity; subsequently, the ZnO:Al films were applied to a CIGS solar cell as a window. CIGS solar cells fabricated with various ZnO:Al films were analyzed in order to investigate their influence. The test results showed that the improvement of ZnO:Al characteristics affects Jsc and Voc in the solar cell through reduced recombination and increase of optical property.

Kerf-Less Exfoliated Thin Silicon Wafer Prepared by Nickel Electrodeposition for Solar Cells.

Ultra-thin and large-area silicon wafers with a thickness in the range of 20-70 µm, were produced by spalling using a nickel stressor layer. A new equation for predicting the thickness of the spalled silicon was derived from the Suo-Hutchinson mechanical model and the kinking mechanism. To confirm the reliability of the new equation, the proportional factor of stress induced by the nickel on the silicon wafer, was calculated. The calculated proportional factor of λ = 0.99 indicates that the thickness of the spalled silicon wafer is proportional to that of the nickel layer. A similar relationship was observed in the experimental data obtained in this study. In addition, the thickness of the stressor layer was converted to a value of stress as a guide when using other deposition conditions and materials. A silicon wafer with a predicted thickness of 50 µm was exfoliated for further analysis. In order to spall a large-area (150 × 150 mm2 or 6 × 6 in2) silicon wafer without kerf loss, initial cracks were formed by a laser pretreatment at a proper depth (50 µm) inside the exfoliated silicon wafer, which reduced the area of edge slope (kerf loss) from 33 to 3 mm2. The variations in thickness of the spalled wafer remained under 4%. Moreover, we checked the probability of degradation of the spalled wafers by using them to fabricate solar cells; the efficiency and ideality factor of the spalled silicon wafers were found to be 14.23%and 1.35, respectively.

Enhanced broadband photoresponse of a self-powered photodetector based on vertically grown SnS layers via the pyro-phototronic effect.

Here, we demonstrate the broadband photoresponse from ultraviolet (365 nm) to near-infrared (850 nm) wavelengths from a photodetector based on vertically grown SnS layers. Particularly, the photoinduced current density of the device increased from 100 to 470 µA cm-2 with a wavelength of 760 nm and an intensity of 7 mW cm-2 by utilizing the pyro-phototronic potential. In addition, the photodetector demonstrated ultrafast response rates of ∼12 µs for the rise and ∼55 µs for the decay times over the studied range. Moreover, a good photoresponsivity of 13 mA W-1 and a high photodetectivity of 3 × 1014 Jones at a wavelength of 760 nm with an intensity of 7 mW cm-2 were measured, representing enhancements of 340% and 3960%, respectively, with the pyroelectric potential. This excellent broadband performance was attributed to the photon-induced pyroelectric effect in the vertically grown SnS layers, which also modulated the optoelectronic processes. This novel approach will open a new avenue to design a broadband ultrafast device for advanced optoelectronics.

Simple Microwave-Assisted Synthesis of Amphiphilic Carbon Quantum Dots from A3/B2 Polyamidation Monomer Set.

Highly fluorescent and amphiphilic carbon quantum dots (CQDs) were prepared by microwave-assisted pyrolysis of citric acid and 4,7,10-trioxa-1,13-tridecanediamine (TTDDA), which functioned as an A3 and B2 polyamidation type monomer set. Gram quantities of fluorescent CQDs were easily obtained within 5 min of microwave heating using a household microwave oven. Because of the dual role of TTDDA, both as a constituting monomer and as a surface passivation agent, TTDDA-based CQDs showed a high fluorescence quantum yield of 29% and amphiphilic solubility in various polar and nonpolar solvents. These properties enable the wide application of TTDDA-based CQDs as nontoxic bioimaging agents, nanofillers for polymer composites, and down-converting layers for enhancing the efficiency of Si solar cells.

Analysis of the Effect of Silicon with Nano-Size Surface Structure on an Electrode Formed Using Screen Printing.

In this paper, we report an investigation into the effects of the texturing size of silicon on the efficiency of a screen-printed Si solar cell. To accomplish this, we produced solar cells with various textured surfaces. The method we used to produce these cells included methods such as anisotropic chemical etching (texturing size of about 4 µm) using a mixed solution of KOH and IPA, reactive ion etching (texturing size of about 0.2 µm), and Ag catalyzed etching (texturing size of about 90 nm). The solar cells with an Ag-catalyzed etching textured structure showed the lowest efficiency of 11.87%, with the highest series resistance of 1.32 Ω. In the case of anisotropic chemical etching, the solar cell had the best efficiency of 17.84%, with the lowest series resistance. This means that the electrodes and silicon surfaces were not well-connected with the nano-sized textured silicon surface. The results revealed that conventional silver paste at an average of 1.6 µm is unsuitable for nano-sized textured Si solar cells.

Effect of an Ag Insertion Layer on the Optical and Electrical Properties of Ga Doped Zinc Oxide Films.

GZO/Ag/GZO films were investigated for use as high quality transparent conductive electrodes. The GZO and Ag films were deposited by RF sputtering and electron beam evaporation, respectively, at room temperature. The effects of Ag thickness and post heat treatment on the structural, electrical and optical properties of these multilayer films were investigated. The insertion of the Ag layer with optimized thickness between the GZO layers and the optimized annealing temperature improved the electrical and optical properties of the GZO/Ag/GZO film due to the very low resistivity and surface plasmon effect of the Ag layer. The best multilayer film exhibited a low resistivity of 2.2 x 10(-5) Ω · cm and a transmittance of 88.9%.

SnO2 nanowire gas sensor operating at room temperature.

The NO2 gas sensor based on SnO2 semiconducting nanowires workable at room temperature has been investigated. The network structure of SnO2 nanowires was fabricated on the electrodes by a simple thermal evaporation process from Sn metal powders and oxygen gas. The diameter of the nanowires was 20-60 nm depending on the processing conditions. When the concentration of NO2 was 10 ppm, the sensitivity of 43, the response time of 38 s, and the recovery time of 25 s were observed at the operating temperature of 200 degrees C. In particular, the operating temperature of the sensor could be decreased down below 50 degrees C by controlling the properties of the nanowires and the structures of the electrodes. The sensitivities were 10-15 when the NO2 concentrations were 10-50 ppm at the operating temperature of 50 degrees C.

Fabrication of metal-coated carbon nanowalls synthesized by microwave plasma enhanced chemical vapor deposition.

In this study, the coating of synthesized carbon nanowalls (CNWs) with various metal layers (Ni, Cu, and W) was investigated. CNWs were synthesized by microwave plasma enhanced chemical vapor deposition (PECVD) with a methane (CH4) and hydrogen (H2) gas mixture on a p-type Si wafer, and then coated with metal films (Ni, Cu, and W) using an RF magnetron sputtering system with four-inch targets. Different sputtering times (5, 10, 20, and 30 min) were established to obtain different thicknesses of the metal layers with which the CNWs were coated. Field emission scanning electron microscopy (FE-SEM) was used to examine the cross-sectional and planar conditions of the CNWs, and energy dispersive spectroscopy (EDS) was used to analyze the CNW elements. The FE-SEM analysis of the cross-sectional and planar images confirmed that the metal layers were synthesized to a depth of 0.5 µm from the surfaces of the CNWs, and to a greater depth at the ends of the CNWs, irrespective of the deposition time and the metal species. The resistivity of the as-deposited CNWs appeared as 4.18 x 10(-3) Ω cm; that of the metal-coated CNWs was slightly lower; and that of the Ni-coated CNWs was the lowest (1.74 x 10(-3) Ω cm). The mobility of the metal-coated CNWs was almost unchanged, and that of the as-deposited CNWs was 1.23 x 10(3) cm2 V(-1) s(-1).

Curcumin could prevent the development of chronic neuropathic pain in rats with peripheral nerve injury.

BACKGROUND: Peripheral nerve injury results in chronic neuropathic pain characterized by allodynia and/or spontaneous pain. It has been suggested that activation of mitogen-activated protein kinases such as extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) contribute to the neuropathic pain. OBJECTIVES: We investigated if curcumin could prevent the development of neuropathic pain in rats with chronic constriction injury (CCI) of the sciatic nerve. METHODS: The animals were divided into 3 groups. In the curcumin treatment group (n = 10), curcumin (50 mg/kg/d PO) was administered once daily from 1 day before CCI to 7 days after CCI. The rats in the sham group (n = 10) and CCI group (n = 10) received a control vehicle. The mechanical allodynia was assessed using von Frey at 1, 3, 5, and 7 days after nerve injury. Western blots were used to evaluate the levels of p-ERK, p-JNK, and phosphorylation of NR1 (p-NR1) subunits of N-methyl-D-aspartate in the spinal dorsal root ganglion. RESULTS: In the CCI group, mechanical allodynia was observed during 7 days after nerve injury. However, curcumin treatment reversed the mechanical allodynia 7 days after nerve ligation. There were no differences in the expression of p-ERK, p-JNK, and p-NR1 between the sham and curcumin groups. However, the expression of p-ERK, p-JNK, and p-NR1 in the CCI group were higher than the sham group and curcumin group, respectively (P < 0.05). CONCLUSIONS: Treatment with curcumin during the early stages of peripheral neuropathy can prevent the development of chronic neuropathic pain.

Influence of various plasma treatment on the properties of carbon nanotubes for composite applications.

In present work, the effects of hydrogen and oxygen plasma treatments on the structural properties of carbon nanotubes (CNTs) synthesized by catalytic CVD (Chemical Vapor Deposition) have been systematically investigated. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy were used to characterize the microstructural changes of the CNTs. The oxygen plasma treatment resulted in that the nanoparticles were appeared at the surface of CNTs. At high r.f. power (300 Watt), the microstructure of CNT was changed from nanotube type to nano particles. Long plasma treatment time changed the CNT morphology dramatically. For hydrogen plasma, however, there was no change in microstructure of CNT From the Raman analysis, the crystallinity of CNT was deteriorated by the plasma treatment, regardless of plasma power, treatment time, and gas types. The CNTs treated in oxygen plasma for 90 min showed excellent dispersion properties in aqueous solution.

Structural, optical, and electrical properties of semiconducting ZnO nanosheets.

ZnO nanosheets were fabricated by an oxygen-assisted carbothermal reduction process and their properties were evaluated. In particular, the FET characteristics and photoluminescence properties of ZnO nanosheets were evaluated. The conduction type of ZnO nanosheets was determined as an n-type and the mobility was 20-40 cm2/ V-s, which is fairly high compared to ZnO nanowires. This might be attributed to the wide conduction area of ZnO nanosheet compared to nanowire structures and their better crystallinity.

A combination of lidocaine (lignocaine) and remifentanil reduces pain during propofol injection.

OBJECTIVE: Pain on injection is a well known adverse effect of propofol. The purpose of this study was to compare the analgesic effect of a lidocaine (lignocaine)/remifentanil combination compared with either lidocaine alone or remifentanil alone during propofol injection for induction of anaesthesia. METHODS: In a randomised, double-blind, prospective trial, 129 patients were allocated to one of three groups (each n = 43) receiving lidocaine 20mg, remifentanil 0.3 microg/kg or lidocaine 20 mg plus remifentanil 0.3 microg/kg as pretreatment, followed by injection of 5 mL of 1% propofol. Pain severity was evaluated on a four-point scale. RESULTS: Two patients (4.7%) complained of pain in the lidocaine plus remifentanil group compared with 15 (35.7%) in the lidocaine alone group and 18 (42.9%) in the remifentanil alone group (p < 0.001). There was no significant difference in the incidence of injection pain between the lidocaine alone and remifentanil alone groups (p = 0.21). CONCLUSION: Pretreatment with a combination of lidocaine and remifentanil is more effective than either pretreatment alone in reducing pain on injection of propofol.