One-dimensional nanostructures, such as nanorod (NR) arrays, are expected to improve the photovoltaic (PV) response of solar cells with an ultrathin absorber due to an increased areal (junction) ...density and light trapping. We report on the deposition of CdS and CdTe:As semiconductor thin films on ZnO NR arrays by means of metalorganic chemical vapour deposition (MOCVD). The change in optical properties of the ZnO NRs upon the growth of CdS shell was monitored and compared to the simulated data, which confirmed the presence of strong light scattering effects in the visible and near infrared regions. The PV performance of nanostructured vs. planar CdS/CdTe solar cells (grown using the material from the same MOCVD run) showed similar conversion efficiencies (~ 4%), despite the current density being lower for the nanostructured cell due to its thicker CdS window. A clear improvement in the quantum efficiency was however observed in the near infrared region, resulting from the light trapping by the ZnO/CdS core-shell NR structure. We also showed that reduction of surface defects and use of high absorber carrier density would boost the efficiency beyond that of planar CdTe solar cells. The reported device performance and the direct observation of light trapping are promising towards optimisation of extremely-thin-absorber CdTe PV devices.
•Extremely thin absorber CdTe thin film solar cells fabricated using ZnO nanorod array films.•Conformal growth of CdS and CdTe shells on ZnO nanorods achieved by MOCVD.•Optical properties and light trapping were studied experimentally and theoretically.•Over 4% conversion efficiency reported using less than 0.5µm CdTe absorber.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Silver nanowire (Ag NW) networks are promising candidates for replacement of indium tin oxide (ITO). However, transparent conductors based on Ag NW networks often suffer from 'haziness' resulting ...from surface roughness. Thus, in addition to achieving suitable transparency and conductivity, surface roughness must be minimized if realistic implementation of Ag NW networks as transparent conductors is to be realized. In this work, we have reduced the surface roughness of Ag NW networks to below 5 nm as compared to 54 nm for as-deposited Ag NWs through optimization of the low temperature annealing treatment and planarization by poly(3,4 ethylenedioxythiophene)-poly(styrenesulfanate). Using this method, we have been able to produce Ag NW networks with transmittances and sheet resistances of 87% and 11Ω sq, respectively. These are some of the best values reported for non-oxide-based transparent conductors. Incorporation of these smooth Ag networks into polymer light emitting diodes fabricated in our laboratory yields device characteristics that are comparable to or better than those with commercially available ITO.
Synthesis of silver‐doped zinc oxide (ZnO:Ag) nanoparticles through precipitation method has been reported. The synthesis was conducted at room temperature and no subsequent thermal treatment was ...applied. ZnO nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), fourier transmission infrared spectroscopy (FTIR), and ultraviolet‐visible (UV–Vis) spectroscopy. Detailed crystallographic investigation was accomplished through Rietveld refinement. The effect of silver content on structural and optical properties of resultant ZnO nanoparticles has been reported. It was found that silver doping results in positional shifts for the XRD peaks and the absorption band edge of ZnO. These were attributed to the substitutional incorporation of Ag+ ions into Zn2+ sites within the ZnO crystal. In addition, higher silver incorporation resulted in smaller size for ZnO nanoparticles. The photocatalytic activity of the ZnO:Ag nanoparticles was also determined by methylene orange (MO) degradation studies and compared to that of undoped ZnO. Improved photocatalytic activity was obtained for ZnO:Ag nanoparticles. It has been shown that an optimum amount of silver dopant is required to obtain maximum photocatalytic activity.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
This paper reports on the integration of zinc oxide nanowires (ZnO NWs) with a silicon on insulator (SOI) CMOS (complementary metal oxide semiconductor) micro-hotplate for use as an alcohol sensor. ...The micro-hotplates consist of a silicon resistive micro-heater embedded within a membrane (composed of silicon oxide and silicon nitride, supported on a silicon substrate) and gold bump bonded aluminum electrodes that are used to make an ohmic contact with the sensing material. ZnO NWs were grown by a simple, low-cost hydrothermal method and characterised using SEM, XRD and photoluminiscence methods. The chemical sensitivity of the on-chip NWs to ethanol vapour (at different humidity levels) was characterised at two different temperatures namely, 300
°C and 400
°C (power consumption was 24
mW and 33
mW, respectively), and the sensitivity was found to be 0.1%/ppm (response 4.7 at 4363
ppm). These results show that ZnO NWs are a promising material for use as a CMOS ethanol gas sensor that offers low cost, low power consumption and integrated circuitry.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hierarchically nanostructured composite electrodes were prepared by the electrodeposition of manganese dioxide nanowires (MnO 2 NWs) with 5–20 nm diameters on electrospun carbon nanofiber (CNF) webs ...with diameters of 250 and 650 nm. The effects of CNF diameters and mass loading of MnO 2 NWs on the hierarchical nanostructure formation and the performance of the composite electrodes were investigated. The internal structure of the composite electrode depended on CNF diameter and mass loading of MnO 2 NW. The electrodes based on thinner CNFs and higher mass loadings of MnO 2 NWs showed higher values of gravimetric and volumetric capacitances. This would be due to MnO 2 NWs forming a dense network in the thinner three-dimensional CNF framework. In addition, asymmetric supercapacitors with the MnO 2 NW/CNF composite electrode as the positive electrode and activated carbon as the negative electrode showed high energy and power densities of 8.9 W h kg −1 and 4.9 kW kg −1 , respectively. These results clearly indicate that the hierarchical network nanostructure composed of an active material and a charge collector can be considered a promising electrode for various electrochemical devices.
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IJS, KILJ, NUK, UL, UM, UPUK
Hard, refractory thin films consisting of group IVB element mono-nitrides deposited using various chemical and physical vapour-deposition techniques are widely used in wear-resistant applications. As ...the demand for performance exceeds the capabilities of existing materials, new materials with superior properties must be developed. Here we report the realization and characterization of hard cubic Zr3N4 (c-Zr3N4) thin films. The films, deposited using a novel but industrially viable modified filtered cathodic arc (FCA) method, undergo a phase transformation from orthorhombic to cubic above a critical stress level of 9 GPa as determined by X-ray diffraction and Raman spectroscopy. The c-Zr3N4 films are significantly harder (approximately 36 GPa) than both the orthorhombic Zr3N4 (o-Zr3N4) and ZrN films (approximately 27 GPa). The ability to deposit this material directly onto components as a thin film will allow its use in wear- and oxidation-resistant applications.
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IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper reports on the synthesis of zinc oxide (ZnO) nanostructures and examines the performance of nanocomposite thin-film transistors (TFTs) fabricated using ZnO dispersed in both n- and p-type ...polymer host matrices. The ZnO nanostructures considered here comprise nanowires and tetrapods and were synthesized using vapor phase deposition techniques involving the carbothermal reduction of solid-phase zinc-containing compounds. Measurement results of nanocomposite TFTs based on dispersion of ZnO nanorods in an n-type organic semiconductor (6, 6-phenyl-C 61 -butyric acid methyl ester) show electron field-effect mobilities in the range 0.3-0.6 cm 2 V -1 s -1 , representing an approximate enhancement by as much as a factor of 40 from the pristine state. The on/off current ratio of the nanocomposite TFTs approach 10 6 at saturation with off-currents on the order of 10 pA. The results presented here, although preliminary, show a highly promising enhancement for realization of high-performance solution-processable n-type organic TFTs.
Indium rich InGaN solar cells grown by MOCVD Çakmak, H.; Arslan, Engin; Rudziński, M. ...
Journal of materials science. Materials in electronics,
08/2014, Volume:
25, Issue:
8
Journal Article
Peer reviewed
Open access
This study focuses on both epitaxial growths of In
x
Ga
1−x
N epilayers with graded In content, and the performance of solar cells structures grown on sapphire substrate by using metal organic ...chemical vapor deposition. The high resolution X-ray and Hall Effect characterization were carried out after epitaxial InGaN solar cell structures growth. The In content of the graded InGaN layer was calculated from the X-ray reciprocal space mapping measurements. Indium contents of the graded InGaN epilayers change from 8.8 to 7.1 % in Sample A, 15.7–7.1 % in Sample B, and 26.6–15.1 % in Sample C. The current voltage measurements of the solar cell devices were carried out after a standard micro fabrication procedure. Sample B exhibits better performance with a short-circuit current density of 6 mA/cm
2
, open-circuit voltage of 0.25 V, fill factor of 39.13 %, and the best efficiency measured under a standard solar simulator with one-sun air mass 1.5 global light sources (100 mW/cm
2
) at room temperature for finished devices was 0.66 %.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this work, both planar and textured, industrial scale (156 mm × 156 mm) single‐crystalline silicon (Si) solar cells have been fabricated using zinc oxide (ZnO) nanorods as antireflection coating ...(ARC). ZnO nanorods were grown in a few minutes via hydrothermal method within a commercially available microwave oven. Relative improvement in excess of 65% in the reflectivity was observed for both planar and textured Si surfaces. Through ZnO nanorods, effective lifetime (τeff) measurements were presented to investigate the surface passivation property of such an ARC layer. ZnO nanorods increased the τeff from 9 to 71 μs at a carrier injection level of 1015 cm−3. Increased carrier lifetime revealed the passivation effect of the ZnO nanorods in addition to their ARC property. 33% and 16% enhancement in the photovoltaic conversion efficiency was obtained in planar and textured single‐crystalline solar cells, respectively. Our results reveal the potential of ZnO nanorods as ARC that can be deposited through simple solution‐based methods and the method investigated herein can be simply adapted to industrial scale fabrication.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
This is a multicenter, prospective study.
The objective of this study was to assess the validity and reliability of the Turkish version of Spinal Cord Independence Measure-III (SCIM-III).
This study ...was conducted in rehabilitation centers of three hospitals in Turkey.
Two-hundred and four (n=204) consecutive patients with spinal cord injury (SCI) were included in the study. Each patient was examined by two physicians. Neurologic impairment was measured according to the American Spinal Injury Association (ASIA) Impairment Scale (AIS) 2000 revised criteria. Backward and forward translation of SCIM-III was performed by native speakers in both languages. To measure the validity of SCIM-III, the scores were compared with patients' AIS grades, total motor scores and the Health Survey Short Form-36 (SF-36) subscale scores. SCIM-III was analyzed for test-retest reliability by the same rater on 49 patients during the follow-up evaluations.
Total agreement values between raters changed between 75.9 and 100%. Kappa values were all above 0.6, and they were statistically significant. The Pearson's correlation values between the raters were very high and statistically significant. The Cronbach's α-values for the two consecutive raters were 0.865 and 0.896. Test-retest reliability was assessed by paired samples t-test, and no significant difference was observed. SCIM-III and SF-36 physical (r=0.339, P<0.005) and general health scores (r=0.200, P<0.005) showed correlation. All subscales of the SCIM-III, with the exception of self-care, had significant differences in comparison with the AIS grades. SCIM-III total and total motor scores showed correlation (r=0.585, P<0.001).
The Turkish version of SCIM-III was found to be valid and reliable.
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DOBA, EMUNI, FIS, FSPLJ, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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