Process Accumulated 8% Efficient Cu2 ZnSnS4 -BiVO4 Tandem Cell for Solar Hydrogen Evolution with the Dynamic Balance of Solar Energy Storage and Conversion.

A process accumulated record solar to hydrogen (STH) conversion efficiency of 8% is achieved on the Cu2 ZnSnS4 -BiVO4 tandem cell by the synergistic coupling effect of solar thermal and photoelectrochemical (PEC) water splitting with the dynamic balance of solar energy storage and conversion of the greenhouse system. This is the first report of a Cu2 ZnSnS4 -BiVO4 tandem cell with a high unbiased STH efficiency of over 8% for solar water splitting due to the greenhouse device system. The greenhouse acts as a solar thermal energy storage cell, which absorbs infrared solar light and storage as thermal energy with the solar light illumination time, while thermoelectric device (TD) converts thermal energy into electric power, electric power is also recycled and added onto Cu2 ZnSnS4 -BiVO4 tandem cell for enhanced overall water splitting. Finally, the solar water splitting properties of the TD-Cu2 ZnSnS4 -BiVO4 integrated tandem cell in pure natural seawater are demonstrated, and a champion STH efficiency of 2.46% is presented, while a large area (25 cm2 ) TD-Cu2 ZnSnS4 -BiVO4 integrated tandem device with superior long-term stability is investigated for 1 week, which provides new insight into photoelectrochemical solar water splitting devices.

Research on the Influence of the Interfacial Properties Between a Cu3 BiS3 Film and an Inx Cd1- x S Buffer Layer for Photoelectrochemical Water Splitting.

The ternary compound photovoltaic semiconductor Cu3 BiS3 thin film-based photoelectrode demonstrates a quite promising potential for photoelectrochemical hydrogen evolution. The presented high onset potential of 0.9 VRHE attracts much attention and shows that the Cu3 BiS3 thin films are quite good as an efficient solar water splitting photoelectrode. However, the CdS buffer does not fit the Cu3 BiS3 thin film: the conduction band offset between CdS and Cu3 BiS3 reaches 0.7 eV, and such a high conduction band offset (CBO) significantly increases the interfacial recombination ratio and is the main reason for the relatively low photocurrent of the Cu3 BiS3 /CdS photoelectrode. In this study, the Inx Cd1- x S buffer layer is found to be significantly lowered the CBO of CBS/buffer and that the In incorporation ratio of the buffer influences the CBO value of the CBS/buffer. The Pt-TiO2 /In0.6 Cd0.4 S/Cu3 BiS3 photocathode exhibits an appreciable photocurrent density of ≈12.20 mA cm-2 at 0 VRHE with onset potential of more than 0.9 VRHE , and the ABPE of the Cu3 BiS3 -based photocathode reaches the highest value of 3.13%. By application of the In0.6 Cd0.4 S buffer, the Cu3 BiS3 -BiVO4 tandem cell presents a stable and excellent unbiased STH of 2.57% for over 100 h.

Effect of heterojunction structures on photoelectrochemical properties of ZnTe-based photocathodes for water reduction.

Photoelectrochemical (PEC) properties of ZnTe-based photocathodes with various structures were investigated to clarify the effective structure for the water reduction reaction. Samples with n-ZnO/ZnTe/p-ZnTe and n-ZnS/ZnTe/p-ZnTe heterostructures showed superior PCE properties to the samples without a heterojunction. In particular, the n-ZnS/ZnTe/p-ZnTe sample exhibited a large photocurrent even at a low applied potential in an electrolyte containing Eu3+ ion as an electron scavenger. Appreciable H2 evolution with a constant rate (approximately 87 µmol cm-2 h-1) was also observed over the sample loaded with Pt deposits under visible-light irradiation (>420 nm): faradaic efficiency of almost 100% was obtained, indicating no unfavorable side reaction occurred in the sample.

Effects of incorporation of Ag into a kesterite Cu2ZnSnS4 thin film on its photoelectrochemical properties for water reduction.

Kesterite Cu2ZnSnS4 (CZTS) thin films in which the Cu site was partially replaced with Ag were prepared by spray deposition on an Mo-coated glass substrate. Successful replacement of Cu components in the CZTS lattice with Ag up to an Ag/(Cu + Ag) ratio of 0.20 was achieved. Samples with relatively low contents of Ag (Ag/(Cu + Ag) ratios of 0.05 and 0.10) showed obvious grain growth compared to that of bare CZTS, whereas samples with higher Ag contents showed an appreciable decrease in grain sizes. Photoelectrochemical properties for water reduction (H2 production), which was examined after surface modifications with an In2S3/CdS double layer and Pt catalyst for H2 evolution, depended strongly on such morphological differences; a maximum conversion efficiency, i.e., half-cell solar to hydrogen efficiency, of 2.4% was achieved by the photocathode based on the film with an Ag/(Cu + Ag) ratio of 0.10. Minority carrier dynamics examined by photoluminescence measurements indicated that such an active sample of PEC H2 production had a relatively long carrier lifetime, suggesting that the suppression of carrier recombination at grain boundaries in the bulk of these kesterite films is one of the important factors for enhancing PEC functions.

Synthesis of nano-sized tungsten oxide particles encapsulated in a hollow silica sphere and their photocatalytic properties for decomposition of acetic acid using Pt as a co-catalyst.

Nano-sized tungsten oxide (WO3) particles, each of which was encapsulated as a core in a hollow silica sphere (WO3@SiO2), were synthesized using calcium tungstate particles as the starting material. The calcium tungstate particles, each of which was covered with a silica shell, were converted to tungstic acid by nitric acid treatment and then to WO3 by heat treatment to obtain WO3@SiO2. A hollow space was formed in WO3@SiO2 between the WO3 core and the SiO2 shell as a result of shrinkage of WO3 during the heat treatment. The thus-obtained WO3@SiO2 was 40 nm in diameter, the WO3 core was 10 nm in diameter, and the silica shell, which was permeable to gas and liquid, was 10 nm in thickness. WO3@SiO2 absorbed visible light to the wavelength of 454 nm, which enabled photocatalytic reaction under visible light; Pt was loaded on the WO3 cores in the photocatalytic reactions. In contrast to Pt-loaded bulk WO3 photocatalysts without an SiO2 shell, Pt-loaded WO3@SiO2 showed continuous and complete decomposition of gaseous acetic acid in air under visible as well as UV irradiation.

Preparation of a CuGaSe2 single crystal and its photocathodic properties.

Chalcopyrite CuGaSe2 single crystals were successfully synthesized by the flux method using a home-made Bridgman-type furnace. The grown crystals were nearly stoichiometric with a Se-poor composition. Although a wafer form of the thus-obtained single crystal showed poor p-type electrical properties due to such unfavorable off-stoichiometry, these properties were found to be improved by applying a post-annealing treatment under Se vapor conditions. As a result, an electrode derived from the Se-treated single crystalline wafer showed appreciable p-type photocurrents. After deposition of a CdS ultrathin layer and a nanoparticulate Pt catalyst on the surface of the electrode, appreciable photoelectrochemical H2 evolution was observed over the modified electrode under photoirradiation by simulated sunlight with application of a bias potential of 0 VRHE.

Brainstem Venous Congestion Caused by Perimedullary Drainage in Anterior Cranial Fossa Dural Arteriovenous Fistula.

BACKGROUND: Myelopathy develops relatively rarely in intracranial dural arteriovenous fistula (DAVF); it has only been reported in posterior cranial fossa DAVF. Herein, we report the first, to our knowledge, case of anterior cranial fossa (ACF) DAVF with myelopathy. CASE DESCRIPTION: A 75-year-old man presented with dizziness, nausea, and gait disturbance. T2-weighted magnetic resonance imaging revealed a hyperintense area in the left cerebellum and medulla; a flow void was also detected around the medulla. The patient was first diagnosed with spinal DAVF, but the shunt point was detected at the anterior ethmoidal artery, flowing from the olfactory vein to the basal vein of Rosenthal and anterior/posterior spinal veins. The shunt point was clipped during craniotomy, and neurologic symptoms improved. CONCLUSIONS: Myelopathy because of intracranial DAVF potentially involves diagnostic pitfalls. Even in ACF DAVF, there is a possibility of myelopathy caused by perimedullary venous drainage.

Environmentally friendly Cu2ZnSnS4-based photocathode modified with a ZnS protection layer for efficient solar water splitting.

High-quality Cu2ZnSnS4 (CZTS) thin films prepared by spray pyrolysis on a Mo-coated glass substrate were used for solar water splitting in this study. Modification of a CdS layer under CZTS improved the photocatalysis efficiency by forming a pn junction between CdS and CZTS, effectively separating the photoexcited carriers without recombination. However, the photocorrosive nature of CdS induces poor stability of the CdS/CZTS photocathode. Surface protection of a CdS-covered CZTS photocathode by a ZnS layer resulted in efficient photoelectrochemical water splitting with a maximum half-cell solar to hydrogen (HC-STH) efficiency of 2.1% and without showing appreciable degradation. The ZnS layer acts as a mediator for efficient electron transport to Pt deposits and as a protective layer, preventing contact between the CdS layer and the outer electrolyte solution.

Effects of Zirconium Doping Into a Monoclinic Scheelite BiVO4 Crystal on Its Structural, Photocatalytic, and Photoelectrochemical Properties.

Effects of zirconium (Zr) doping into BiVO4 powder on its structural properties and photocatalytic activity for O2 evolution were examined. The formation of BiVO4 powder crystallized in a monoclinic scheelite structure (ms-BiVO4) was achieved when the sample was doped with a relatively small amount of Zr. The photocatalytic activity of Zr-doped ms-BiVO4 powder was much higher than that of non-doped ms-BiVO4. However, further doping caused a reduction of photocatalytic activity for O2 evolution due to the occurrence of structural alterations into tetragonal scheelite and tetragonal zircon structures. Similar effects of Zr doping were also observed for the photoelectrochemical (PEC) system based on BiVO4 thin films doped with various amounts of Zr. Thus, Zr doping was confirmed to be effective for improvements of photocatalytic and PEC functions of BiVO4 for water oxidation.

Structural and Solar Cell Properties of a Ag-Containing Cu2ZnSnS4 Thin Film Derived from Spray Pyrolysis.

A silver (Ag)-incorporated kesterite Cu2ZnSnS4 (CZTS) thin film was fabricated by a facile spray pyrolysis method. Crystallographic analyses indicated successful incorporation of various amounts of Ag up to a Ag/(Ag + Cu) ratio of ca. 0.1 into the crystal lattice of CZTS in a homogeneous manner without formation of other impurity compounds. From the results of morphological investigations, Ag-incorporated films had larger crystal grains than the CZTS film. The sample with a relatively low Ag content (Ag/(Ag + Cu) of ca. 0.02) had a compact morphology without appreciable voids and pinholes. However, an increase in the Ag content in the CZTS film (Ag/(Ag + Cu) ca. 0.10) induced the formation of a large number of pinholes. As can be expected from these morphological properties, the best sunlight conversion efficiency was obtained by the solar cell based on the film with Ag/(Ag + Cu) of ca. 0.02. Electrostructural analyses of the devices suggested that the Ag-incorporated film in the device achieved reduction in the amounts of unfavorable copper on zinc antisite defects compared to the bare CZTS film. Moreover, the use of a Ag-incorporated film improved band alignment at the CdS(buffer)-CZTS interface. These alterations should also contribute to enhancement of device properties.

Effects of TiCl4 treatment on the structural and electrochemical properties of a porous TiO2 layer in CH3NH3PbI3 perovskite solar cells.

The effects of surface treatment with TiCl4 on the structural and electrochemical properties of a porous titanium oxide (pTiO2) layer deposited on a fluorine-doped tin oxide (FTO)/glass substrate covered with a dense TiO2 layer (pTiO2/dTiO2/FTO/glass) were systematically investigated in order to obtain an optimum pTiO2 layer for use in CH3NH3PbI3 perovskite solar cells. As confirmed by thermal desorption spectroscopy (TDS) analyses, the amount of surface hydroxyl groups in pTiO2 varied when the pTiO2/dTiO2/FTO/glass sample was treated with solutions with different concentrations of TiCl4 (i.e., 20, 50, 80, and 100 mM). Photoelectrochemical (PEC) analyses of the pTiO2/dTiO2/FTO/glass samples after TiCl4 treatment showed significant increments of photocurrent densities compared to the pTiO2/dTiO2/FTO/glass sample without TiCl4 treatment regardless of the concentration of TiCl4 used in the solution. Electrochemical impedance spectroscopy (EIS) analyses of the TiCl4-treated pTiO2/dTiO2/FTO/glass samples also indicated a lower recombination probability with an increase in TiCl4 concentration. The results suggest that TiCl4 treatment resulted in passivation of defect sites on the surface of the TiO2 nanoparticles as well as improvement of the interconnectivity between the TiO2 nanoparticles in pTiO2. In contrast, the power conversion efficiencies (PCEs) and short circuit current densities of CH3NH3PbI3 perovskite solar cells based on these pTiO2/dTiO2/FTO/glass samples exhibited volcano-like patterns depending on the TiCl4 concentration used for the pTiO2 treatment: the highest PCE was obtained by using pTiO2/dTiO2/FTO/glass treated with 50 mM of TiCl4 solution. Structural analysis of the CH3NH3PbI3 perovskite part performed by X-ray diffraction (XRD) indicated that the formation of CH3NH3PbI3 perovskite was inhibited by the presence of surface hydroxyl groups in the pTiO2 film without TiCl4 treatment. TiCl4 treatment using TiCl4 solutions with concentrations up to 50 mM enhanced the formation of the CH3NH3PbI3 perovskite layer, whereas TiCl4 treatment using TiCl4 solutions with concentrations higher than 50 mM was detrimental due to the formation of nanoparticulate TiO2 aggregates that induce poor porosity and act as recombination sites.

Photoelectrochemical water reduction over wide gap (Ag,Cu)(In,Ga)S2 thin film photocathodes.

The effects of partial replacement of Cu with Ag in a Cu(In,Ga)S2 (CIGS) thin film on its structural, optical, electrostructural, and photoelectrochemical (PEC) properties were investigated, in order to improve its performance for PEC water reduction under sunlight illumination. Results from X-ray diffraction (XRD) analyses revealed the successful partial replacement of Cu with Ag to form solid-solutions with different Ag/(Ag + Cu) ratios (A(x)CIGS, x = Ag/(Ag + Cu) = 0.1, 0.2, 0.3 and 0.4), as confirmed by a gradual change in the (112) reflections to smaller 2θ angles with increasing Ag/(Ag + Cu) ratio. Analyses of the photoabsorption properties of the materials using photoacoustic spectroscopy indicated changes in the band gap energies associated with increasing the Ag/(Ag + Cu) ratio. In addition, valence band maximum potentials of A(x)CIGS were deepened gradually with increasing Ag/(Ag + Cu) ratio. After modifying these A(x)CIGS films with a CdS ultrathin (ca. 70 nm) layer and a Pt catalyst, the PEC water reduction properties were evaluated in an electrolyte solution with the pH adjusted to 6.5, under simulated sunlight (AM 1.5G) radiation. Compared to the CdS- and Pt-modified Ag-free A(x)CIGS (A(0)CIGS) films, appreciable enhancements in the PEC properties were observed for electrodes based on A(x)CIGS (x > 0) films, and the best PEC performance was obtained for the electrode based on the A(0.2)CIGS film. However, the electrode derived from the A(x)CIGS film with Ag/(Ag + Cu) ratios higher than 0.3 showed diminished PEC properties due to the partial conversion of its semiconducting properties from p-type to n-type.

[A Case Report of Spontaneous Cerebrospinal Fluid Otorrhea].

Spontaneous cerebrospinal fluid(CSF)otorrhea is less common than CSF leakage caused by trauma, and rarely occurs in adults. We report an adult case of CSF otorrhea. A 71-year-old woman with no traumatic or otologic history was hospitalized due to bacterial meningitis. After hospitalization, CSF leakage started suddenly from the left external ear canal. A high resolution CT scan with intrathecal administration of contrast material revealed CSF leakage in the left ear canal and multiple bone erosions in both the tegmen mastoideum and the posterior fossa aspect of the petrous bone. We performed closure and surgery via the middle fossa approach. We identified a bone defect in the tegmen mastoideum but could not detect any obvious abnormality in the dura mater. We placed both a pericranial flap and a free abdominal fat on the middle base of the skull as sealing materials. There was no recurrence of CSF otorrhea following surgery. In this surgery, the use of a multilayered closure technique is very important to avoid the recurrence of CSF leakage.

Impact of Precursor Compositions on the Structural and Photovoltaic Properties of Spray-Deposited Cu2 ZnSnS4 Thin Films.

Pure sulfide Cu2 ZnSnS4 thin films were fabricated on Mo-coated glass substrates by facile spray deposition of aqueous precursor solutions containing Cu(NO3 )2 , Zn(NO3 )2 , Sn(CH3 SO3 )2 , and thiourea followed by annealing at 600 °C. When a precursor solution containing a stoichiometric composition of Cu, Zn, and Sn was used, the resulting Cu2 ZnSnS4 thin film contained a Cu2-x S impurity phase owing to the evaporation of Sn components during the annealing process. The Cu2-x S impurity in the Cu2 ZnSnS4 thin film was removed by reducing the concentration of Cu in the precursor solution. This resulted in an improvement of the structural features (i.e., grain sizes and compactness) as well as the electric properties such as acceptor densities, the nature of the acceptor defects, and carrier lifetimes. A solar cell based on the Cu2 ZnSnS4 film with an empirically optimal composition showed conversion efficiency of 8.1 %. The value achieved was one of the best efficiencies of Cu2 ZnSnS4 -based cells derived from a non-vacuum process.

Pt/In2S3/CdS/Cu2ZnSnS4 Thin Film as an Efficient and Stable Photocathode for Water Reduction under Sunlight Radiation.

An electrodeposited Cu2ZnSnS4 (CZTS) compact thin film modified with an In2S3/CdS double layer and Pt deposits (Pt/In2S3/CdS/CZTS) was used as a photocathode for water splitting of hydrogen production under simulated sunlight (AM 1.5G) radiation. Compared to platinized electrodes based on a bare CZTS film (Pt/CZTS) and a CZTS film modified with a CdS single layer (Pt/CdS/CZTS), the Pt/In2S3/CdS/CZTS electrode exhibited a significantly high cathodic photocurrent. Moreover, the coverage of the In2S3 layer was found to be effective for stabilization against degradation induced by photocorrosion of the CdS layer. Bias-free water splitting with a power conversion efficiency of 0.28% was achieved by using a simple two-electrode cell consisting of the Pt/In2S3/CdS/CZTS photocathode and a BiVO4 photoanode.

Investigation of the Electric Structures of Heterointerfaces in Pt- and In2S3-Modified CuInS2 Photocathodes Used for Sunlight-Induced Hydrogen Evolution.

Copper indium disulfide (CuInS2) modified with an In2S3 layer and a Pt catalyst showed a more efficient photoelectrochemical (PEC) property for hydrogen evolution from a nearly neutral (pH 6) 0.2 M NaH2PO4 solution under simulated sunlight illumination (AM 1.5G) than that of a CuInS2 electrode modified with a CdS layer and a Pt catalyst. Analysis of the PEC properties of In2S3-modified CuInS2 (In2S3/CuInS2) and CdS-modified CuInS2 (CdS/CuInS2) in solutions containing an electron scavenger (Eu(3+)) showed identical enhancement of the PEC properties of In2S3/CuInS2 when compared to those of CdS/CuInS2, indicating the formation of a favorable heterointerface in In2S3/CuInS2 for efficient charge separation. Spectroscopic evaluation of conduction band offsets revealed that In2S3/CuInS2 had a notch-type conduction band offset, whereas a cliff-type offset was formed in CdS/CuInS2: these results also revealed a better interface electric structure of In2S3/CuInS2 than that of CdS/CuInS2.

Clinical outcomes of prostate cancer patients in Yokosuka City, Japan: A comparative study between cases detected by prostate-specific antigen-based screening in Yokosuka and those detected by other means.

OBJECTIVES: To investigate whether prostate-specific antigen-based screening reduced the prostate cancer mortality rate in Yokosuka, Japan. METHODS: We carried out a cohort study, in which we compared clinical outcomes between patients detected by prostate-specific antigen-based screening (S group n = 524) versus those detected by other means (NS group n = 1044). Clinical and pathological factors were evaluated using Cox regression analyses and the Kaplan-Meier method. RESULTS: A total of 1.5% (8/524) of patients in the S group and 6.7% (70/1044) of those in the NS group died from prostate cancer during follow up. A total of 8.0% (42/524) of patients in the S group and 11.4% (119/1044) in the NS group died from other causes. The 10-year cancer specific survival rates of the S and NS groups were 97% and 86%, respectively (P < 0.001). The median age was significantly lower in the S group than the NS group: 71 and 73 years, respectively (P < 0.001). The rate of Gleason score 8-10 was significantly lower in the S group than the NS group: 9.7% and 16.7%, respectively (P < 0.001). The rate of patients with metastasis or prostate-specific antigen 100 ng/mL or more was significantly lower in the S group than the NS group: 7.8% and 23.0%, respectively (P < 0.001). On multivariate analysis, Gleason score 8-10 compared with Gleason score 6 was independently associated with cancer-specific survival (hazard ratio 4.808, 95% confidence interval 1.044-22.14, P = 0.044). CONCLUSIONS: Prostate-specific antigen-based population screening in Yokosuka City might help to reduce the prostate cancer mortality rate.

Cu(In,Ga)(S,Se)2 thin film solar cell with 10.7% conversion efficiency obtained by selenization of the Na-doped spray-pyrolyzed sulfide precursor film.

Selenium-rich Cu(In,Ga)(S,Se)2 (CIGSSe) thin films on an Mo-coated soda-lime glass substrate were fabricated by spray pyrolysis of an aqueous precursor solution containing Cu(NO3)2, In(NO3)3, Ga(NO3)3, and thiourea followed by selenization at 560 °C for 10 min. We studied the effects of intentional sodium addition on the structural and morphological properties of the fabricated CIGSSe films by dissolving NaNO3 in the aqueous precursor solution. The addition of sodium was found to affect the morphology of the final CIGSSe film: the film had denser morphology than that of the CIGSSe film obtained without addition of NaNO3. Photoelectrochemical measurements also revealed that the acceptor density of the nondoped CIGSSe film was relatively high (N(a) = 7.2 × 10(17) cm(-3)) and the addition of sodium led to a more favorable value for solar cell application (N(a) = 1.8 × 10(17) cm(-3)). As a result, a solar cell based on the sodium-modified CIGSSe film exhibited maximum conversion efficiency of 8.8%, which was significantly higher than that of the cell based on nondoped CIGSSe (4.4%). In addition, by applying MgF2 antireflection coating to the device, the maximum efficiency was further improved to 10.7%.

Enhancement of solar hydrogen evolution from water by surface modification with CdS and TiO2 on porous CuInS2 photocathodes prepared by an electrodeposition-sulfurization method.

Porous films of p-type CuInS2, prepared by sulfurization of electrodeposited metals, are surface-modified with thin layers of CdS and TiO2. This specific porous electrode evolved H2 from photoelectrochemical water reduction under simulated sunlight. Modification with thin n-type CdS and TiO2 layers significantly increased the cathodic photocurrent and onset potential through the formation of a p-n junction on the surface. The modified photocathodes showed a relatively high efficiency and stable H2 production under the present reaction conditions.