Seigo Ito - Academia.edu (original) (raw)

Papers by Seigo Ito

The Japan Society of Applied Physics, 2016

Energy Technology, 2018

Organic‐inorganic CH3NH3PbI3‐based perovskite solar cells have received significant research inte... more Organic‐inorganic CH3NH3PbI3‐based perovskite solar cells have received significant research interest; however, thermal stability issue still remains. Carbon‐based triple‐porous‐layer perovskite solar cells without any hole transporting material were selected in order to investigate the internal degradation process by thermal stresses. The sealed perovskite solar cells at 100 °C showed stable performance in the power conversion efficiency up to 4500 h, but the degradation was accelerated after that. By analyzing the perovskite solar cells aged for 7000 h at 100 °C, the results of energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy suggest that, although Pb, I, and N were sealed inside of the devices, a plenty amount of CH3NH3+ deactivated in the sealant UV‐curable adhesive at 100 °C, which is the reason of the thermal degradation for the sealed perovskite solar cells.

Photonics, 2021

We applied room-temperature photoluminescence (PL) spectroscopy for the compositional engineering... more We applied room-temperature photoluminescence (PL) spectroscopy for the compositional engineering of a CH3NH3Pb(Cl,I)3 light harvester in an alloy-based perovskite solar cell. This spectroscopic characterization determines the optimal Cl concentration where the power conversion efficiency shows its maximum in a contactless and non-destructive manner. The PL quenching ratio evaluated from the comparative PL studies between the films grown on glass/ZrO2 and SnO2:F/TiO2 substrates exhibited its maximum at a Cl concentration of 10 mol%, which agrees with the Cl concentration determined from the current–voltage measurement-based device performance. We also discuss the possible reasons for the coincidence mentioned above regarding the charge extraction effect induced by Cl incorporation.

Journal of Power Sources, 2016

The photovoltaic performance of a perovskite solar cell based on a new electron conducting SnO2 f... more The photovoltaic performance of a perovskite solar cell based on a new electron conducting SnO2 film prepared at low temperature using different solvents was investigated. SnO2 was selected as an electron conducting medium due to its superior properties over TiO2, such as better antireflective properties, higher electron mobility, more suitable band edges and a wider band gap. A SnO2 layer was developed by spin-coating SnCl2 solution followed by annealing at 200°C in air. The low-temperature (200 °C) annealed SnO2 layer exhibits enhanced crystallization, high transmittance, and uniform surface morphology using ethanol as a solvent rather than water. Solid state CuSCN hole conductor was used as HTM for reducing the device cost. A planar solar cell fabricated with CH3NH3PbI3 perovskite infiltrated SnO2 showed a power conversion efficiency of 8.38% with short-circuit current density of 18.99 mA/cm 2 , an open-circuit voltage of 0.96 mV and a fill factor of 45%. The devices were fabricated at >60% humidity level at room temperature. The results suggest that SnO2 is an effective charge collection system for CH3NH3PbI3 based planar perovskite solar cells. In addition, these results

Energy Science and Technology, Nov 30, 2012

AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase... more AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase was obtained in the powder after ball milling from the mixture of elements (Ag, In, and Te). AgInTe 2 particles had the variation in the size and the biggest particle was approximately 2 µm. AgInTe 2 solar cells were fabricated as <AgInTe 2 / In 2 S 3 /TiO 2 /FTO> superstrate structure by doctor-blade printing, and were annealed at various temperatures under nitrogen ambient. AgInTe 2 after annealing showed high crystallinity and two band gaps of 0.67 and 0.86 eV. Although no photocurrent was observed after annealing below 350 °C, the photocurrent was observed in AgInTe 2 superstrate solar cells after annealing over 400 °C. The short-circuit photocurrent density strongly increased up to 18 mA/cm 2 for the samples annealed at 600 °C for 5 min.

Solar Energy, 2015

In this work silver nanowires were used as the transparent conductive electrode on a crystalline ... more In this work silver nanowires were used as the transparent conductive electrode on a crystalline silicon solar cell in place of the commonly used screen printed grid. Light transmission and surface characterisation of the cells displays an average of 22% more light transmission than the physical non-AgNW shaded area of the cell surface. Further to this it is observed that plasmonic effects result in an increased scattering of incoming light into the cell, which also reduced the amount of light reflected from the cell's front plane. The cells with silver nanowire electrodes did not, however, show improved current-voltage characteristics compared to cells without a front electrode. This is attributed to the overall low light transmission as a result of silver nanoparticles present in the electrodes and poor electrical connection between silicon cell and electrode. Finally, a large reduction in the mass of silver used for the nanowire electrodes was observed when compared to standard screen printed grid fingers.

Natural Resources, 2013

Cu-Zn-S (CZS) films were deposited by the spray pyrolysis method. As-deposited CZS film showed a ... more Cu-Zn-S (CZS) films were deposited by the spray pyrolysis method. As-deposited CZS film showed a low crystallinity. The resistivity of CZS film with   Cu Cu Zn  ratio of 50% is around 2 10 cm    n 2 : 2 : 3. The CZS film elements using spray solution with thiourea was confirmed as  Cu-Zn 1:1   Cu : Zn : S  by ICP-MS and EDX. The band gap of CZS films was varied in the range of 1.8-3.5 ev when the   Cu Cu Zn  ratio was increased from 0% to 67%; CZS film with   Cu Cu Zn  ratio of 50% showed an wide band gap of 2 eV. The photovoltaic characteristics were confirmed with cell structure of 2 2 3 Glass FTO TiO In S CZS carbon. The best cell was observed at the CZS films with   Cu Cu Zn  ratio of 50%; these cells depicted a conversion efficiency of 1.7%.

Nanoscale research letters, 2014

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a s... more The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coat...

SPIE Newsroom, 2013

Hot-injection synthesis of copper indium sulfide produces suitable ink for printed photovoltaic d... more Hot-injection synthesis of copper indium sulfide produces suitable ink for printed photovoltaic devices.

Journal of the American Chemical Society, 2006

Journal of the American Chemical Society, 2005

Inorganic Chemistry, 2006

A ruthenium complex trans-[Ru(L)(NCS) 2 ], L) 4,4′′′-di-tert-butyl-4′,4′′-bis(carboxylic acid)-2,... more A ruthenium complex trans-[Ru(L)(NCS) 2 ], L) 4,4′′′-di-tert-butyl-4′,4′′-bis(carboxylic acid)-2,2′:6′,2′′:6′′,2′′′quaterpyridine (N886), was synthesized and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the N886 complex shows metal-to-ligand charge-transfer transitions in the entire visible region and quasi-reversible oxidation and reduction potentials at E 1/2) +0.38 and −1.92 V vs ferrocene, respectively. The electronic spectra of the N886 complex were calculated by density functional theory (DFT)−time-dependent DFT, which qualitatively reproduces the experimental absorption spectra for both the protonated and deprotonated species. From the analysis of the computed optical transitions of N886, we assign its absorption bands as mixed Ru/SCN-to-quaterpyridine charge-transfer transitions, which extend from the near-IR to the UV regions. The panchromatic response of the N886 complex renders it as a suitable sensitizer for solar energy conversion applications based on titanium dioxide mesoporous electrodes. The preliminary results using the N886 complex as a sensitizer in a dye-sensitized solar cell, with an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I 2 , and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio 1:1), show 40% incident photonto-current efficiencies, yielding under standard AM 1.5 sunlight a short-circuit photocurrent density of 11.8 ± 0.2 mA/cm 2 , an open-circuit voltage of 680 ± 30 mV, and a fill factor of 0.73 ± 0.03, corresponding to an overall conversion efficiency of 5.85%.

Chemistry of Materials, 2003

Conductive transparent thin films made of multilayer coatings consisting of three alternative lay... more Conductive transparent thin films made of multilayer coatings consisting of three alternative layers (TiO 2 /Ag/TiO 2 , TAT) have been applied to dye-sensitized solar cells (DSCs). We have used sputtering deposition to prepare the transparent layers and measured the optical properties. Mesoporous TiO 2 electrodes for DSCs were coated on TAT by a spincoating and low-temperature sintering method. They were compared to well-known transparent metal oxide glasses (ITO and F-doped SnO 2). These DSCs on the TAT coatings yielded a short-circuit photocurrent density of 9 mA/cm 2 , a photocurrent of 700 mV, and an overall cell efficiency of 3.9% at one sun light intensity.

Chemical Communications, 2008

International Journal of Nanotechnology, 2013

AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase... more AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase was obtained in the powder after ball milling from the mixture of elements (Ag, In, and Te). AgInTe 2 particles had the variation in the size and the biggest particle was approximately 2 µm. AgInTe 2 solar cells were fabricated as <AgInTe 2 / In 2 S 3 /TiO 2 /FTO> superstrate structure by doctor-blade printing, and were annealed at various temperatures under nitrogen ambient. AgInTe 2 after annealing showed high crystallinity and two band gaps of 0.67 and 0.86 eV. Although no photocurrent was observed after annealing below 350 °C, the photocurrent was observed in AgInTe 2 superstrate solar cells after annealing over 400 °C. The short-circuit photocurrent density strongly increased up to 18 mA/cm 2 for the samples annealed at 600 °C for 5 min.

Energy Science and Technology, May 31, 2012

Abstract CuInSe 2 powders synthesized by ball milling were printed on In 2 S 3/TiO 2/FTO/glass su... more Abstract CuInSe 2 powders synthesized by ball milling were printed on In 2 S 3/TiO 2/FTO/glass substrates, resulting in superstrate solar cells. Although particle structure of CuInSe 2 in the layer remained after heating at 600 C under N 2 gas, photovoltaic effects ...

The Japan Society of Applied Physics, 2016

Energy Technology, 2018

Organic‐inorganic CH3NH3PbI3‐based perovskite solar cells have received significant research inte... more Organic‐inorganic CH3NH3PbI3‐based perovskite solar cells have received significant research interest; however, thermal stability issue still remains. Carbon‐based triple‐porous‐layer perovskite solar cells without any hole transporting material were selected in order to investigate the internal degradation process by thermal stresses. The sealed perovskite solar cells at 100 °C showed stable performance in the power conversion efficiency up to 4500 h, but the degradation was accelerated after that. By analyzing the perovskite solar cells aged for 7000 h at 100 °C, the results of energy dispersive X‐ray spectroscopy and Fourier transform infrared spectroscopy suggest that, although Pb, I, and N were sealed inside of the devices, a plenty amount of CH3NH3+ deactivated in the sealant UV‐curable adhesive at 100 °C, which is the reason of the thermal degradation for the sealed perovskite solar cells.

Photonics, 2021

We applied room-temperature photoluminescence (PL) spectroscopy for the compositional engineering... more We applied room-temperature photoluminescence (PL) spectroscopy for the compositional engineering of a CH3NH3Pb(Cl,I)3 light harvester in an alloy-based perovskite solar cell. This spectroscopic characterization determines the optimal Cl concentration where the power conversion efficiency shows its maximum in a contactless and non-destructive manner. The PL quenching ratio evaluated from the comparative PL studies between the films grown on glass/ZrO2 and SnO2:F/TiO2 substrates exhibited its maximum at a Cl concentration of 10 mol%, which agrees with the Cl concentration determined from the current–voltage measurement-based device performance. We also discuss the possible reasons for the coincidence mentioned above regarding the charge extraction effect induced by Cl incorporation.

Journal of Power Sources, 2016

The photovoltaic performance of a perovskite solar cell based on a new electron conducting SnO2 f... more The photovoltaic performance of a perovskite solar cell based on a new electron conducting SnO2 film prepared at low temperature using different solvents was investigated. SnO2 was selected as an electron conducting medium due to its superior properties over TiO2, such as better antireflective properties, higher electron mobility, more suitable band edges and a wider band gap. A SnO2 layer was developed by spin-coating SnCl2 solution followed by annealing at 200°C in air. The low-temperature (200 °C) annealed SnO2 layer exhibits enhanced crystallization, high transmittance, and uniform surface morphology using ethanol as a solvent rather than water. Solid state CuSCN hole conductor was used as HTM for reducing the device cost. A planar solar cell fabricated with CH3NH3PbI3 perovskite infiltrated SnO2 showed a power conversion efficiency of 8.38% with short-circuit current density of 18.99 mA/cm 2 , an open-circuit voltage of 0.96 mV and a fill factor of 45%. The devices were fabricated at >60% humidity level at room temperature. The results suggest that SnO2 is an effective charge collection system for CH3NH3PbI3 based planar perovskite solar cells. In addition, these results

Energy Science and Technology, Nov 30, 2012

AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase... more AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase was obtained in the powder after ball milling from the mixture of elements (Ag, In, and Te). AgInTe 2 particles had the variation in the size and the biggest particle was approximately 2 µm. AgInTe 2 solar cells were fabricated as <AgInTe 2 / In 2 S 3 /TiO 2 /FTO> superstrate structure by doctor-blade printing, and were annealed at various temperatures under nitrogen ambient. AgInTe 2 after annealing showed high crystallinity and two band gaps of 0.67 and 0.86 eV. Although no photocurrent was observed after annealing below 350 °C, the photocurrent was observed in AgInTe 2 superstrate solar cells after annealing over 400 °C. The short-circuit photocurrent density strongly increased up to 18 mA/cm 2 for the samples annealed at 600 °C for 5 min.

Solar Energy, 2015

In this work silver nanowires were used as the transparent conductive electrode on a crystalline ... more In this work silver nanowires were used as the transparent conductive electrode on a crystalline silicon solar cell in place of the commonly used screen printed grid. Light transmission and surface characterisation of the cells displays an average of 22% more light transmission than the physical non-AgNW shaded area of the cell surface. Further to this it is observed that plasmonic effects result in an increased scattering of incoming light into the cell, which also reduced the amount of light reflected from the cell's front plane. The cells with silver nanowire electrodes did not, however, show improved current-voltage characteristics compared to cells without a front electrode. This is attributed to the overall low light transmission as a result of silver nanoparticles present in the electrodes and poor electrical connection between silicon cell and electrode. Finally, a large reduction in the mass of silver used for the nanowire electrodes was observed when compared to standard screen printed grid fingers.

Natural Resources, 2013

Cu-Zn-S (CZS) films were deposited by the spray pyrolysis method. As-deposited CZS film showed a ... more Cu-Zn-S (CZS) films were deposited by the spray pyrolysis method. As-deposited CZS film showed a low crystallinity. The resistivity of CZS film with   Cu Cu Zn  ratio of 50% is around 2 10 cm    n 2 : 2 : 3. The CZS film elements using spray solution with thiourea was confirmed as  Cu-Zn 1:1   Cu : Zn : S  by ICP-MS and EDX. The band gap of CZS films was varied in the range of 1.8-3.5 ev when the   Cu Cu Zn  ratio was increased from 0% to 67%; CZS film with   Cu Cu Zn  ratio of 50% showed an wide band gap of 2 eV. The photovoltaic characteristics were confirmed with cell structure of 2 2 3 Glass FTO TiO In S CZS carbon. The best cell was observed at the CZS films with   Cu Cu Zn  ratio of 50%; these cells depicted a conversion efficiency of 1.7%.

Nanoscale research letters, 2014

The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a s... more The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coat...

SPIE Newsroom, 2013

Hot-injection synthesis of copper indium sulfide produces suitable ink for printed photovoltaic d... more Hot-injection synthesis of copper indium sulfide produces suitable ink for printed photovoltaic devices.

Journal of the American Chemical Society, 2006

Journal of the American Chemical Society, 2005

Inorganic Chemistry, 2006

A ruthenium complex trans-[Ru(L)(NCS) 2 ], L) 4,4′′′-di-tert-butyl-4′,4′′-bis(carboxylic acid)-2,... more A ruthenium complex trans-[Ru(L)(NCS) 2 ], L) 4,4′′′-di-tert-butyl-4′,4′′-bis(carboxylic acid)-2,2′:6′,2′′:6′′,2′′′quaterpyridine (N886), was synthesized and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the N886 complex shows metal-to-ligand charge-transfer transitions in the entire visible region and quasi-reversible oxidation and reduction potentials at E 1/2) +0.38 and −1.92 V vs ferrocene, respectively. The electronic spectra of the N886 complex were calculated by density functional theory (DFT)−time-dependent DFT, which qualitatively reproduces the experimental absorption spectra for both the protonated and deprotonated species. From the analysis of the computed optical transitions of N886, we assign its absorption bands as mixed Ru/SCN-to-quaterpyridine charge-transfer transitions, which extend from the near-IR to the UV regions. The panchromatic response of the N886 complex renders it as a suitable sensitizer for solar energy conversion applications based on titanium dioxide mesoporous electrodes. The preliminary results using the N886 complex as a sensitizer in a dye-sensitized solar cell, with an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I 2 , and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio 1:1), show 40% incident photonto-current efficiencies, yielding under standard AM 1.5 sunlight a short-circuit photocurrent density of 11.8 ± 0.2 mA/cm 2 , an open-circuit voltage of 680 ± 30 mV, and a fill factor of 0.73 ± 0.03, corresponding to an overall conversion efficiency of 5.85%.

Chemistry of Materials, 2003

Conductive transparent thin films made of multilayer coatings consisting of three alternative lay... more Conductive transparent thin films made of multilayer coatings consisting of three alternative layers (TiO 2 /Ag/TiO 2 , TAT) have been applied to dye-sensitized solar cells (DSCs). We have used sputtering deposition to prepare the transparent layers and measured the optical properties. Mesoporous TiO 2 electrodes for DSCs were coated on TAT by a spincoating and low-temperature sintering method. They were compared to well-known transparent metal oxide glasses (ITO and F-doped SnO 2). These DSCs on the TAT coatings yielded a short-circuit photocurrent density of 9 mA/cm 2 , a photocurrent of 700 mV, and an overall cell efficiency of 3.9% at one sun light intensity.

Chemical Communications, 2008

International Journal of Nanotechnology, 2013

AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase... more AgInTe 2 micron-particles were synthesized by mechanical ball milling method. Only AgInTe 2 phase was obtained in the powder after ball milling from the mixture of elements (Ag, In, and Te). AgInTe 2 particles had the variation in the size and the biggest particle was approximately 2 µm. AgInTe 2 solar cells were fabricated as <AgInTe 2 / In 2 S 3 /TiO 2 /FTO> superstrate structure by doctor-blade printing, and were annealed at various temperatures under nitrogen ambient. AgInTe 2 after annealing showed high crystallinity and two band gaps of 0.67 and 0.86 eV. Although no photocurrent was observed after annealing below 350 °C, the photocurrent was observed in AgInTe 2 superstrate solar cells after annealing over 400 °C. The short-circuit photocurrent density strongly increased up to 18 mA/cm 2 for the samples annealed at 600 °C for 5 min.

Energy Science and Technology, May 31, 2012

Abstract CuInSe 2 powders synthesized by ball milling were printed on In 2 S 3/TiO 2/FTO/glass su... more Abstract CuInSe 2 powders synthesized by ball milling were printed on In 2 S 3/TiO 2/FTO/glass substrates, resulting in superstrate solar cells. Although particle structure of CuInSe 2 in the layer remained after heating at 600 C under N 2 gas, photovoltaic effects ...