ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye fi... more ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye films. The radiation sensitivity and spectral resolution were improved significantly by approaches, indicating the realization of integrated flow-cytometry chips. OCIS codes: (230.5170) Photodiodes; (160.4890) Organic materials
This paper presents a novel approach for fabricating lead-based layered perovskite films. The per... more This paper presents a novel approach for fabricating lead-based layered perovskite films. The perovskite structure was formed during the transfer of a perovskite-unform monolayer onto a substrate. ...
Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenyleth... more Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, CaI2, CdI2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of PbI-based layered perovskite mixed with CaI-based layered perovskite (20 molar%) is about 5 times large that of the pristine PbI-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-b...
Lead-halide based layered perovskite compounds (RNH3)2PbX4 self-organize organic-inorganic superl... more Lead-halide based layered perovskite compounds (RNH3)2PbX4 self-organize organic-inorganic superlattice which two-dimensional inorganic semiconductor layer consisting of corner-sharing PbX6 octahedra and organic ammonium RNH3 layered are alternately piled up. Owing to the low dimensional semiconductor nature, they form stable exciton having large binding energy of several hundred meV and exhibit effcient exciton emission, electroluminescence and optical nonlinearity. In this report, we present optical properties of the layered perovskites and their application for EL device, improvement of exciton emission effciency by cation mixing for highly efficient emissive devices, and development of preparation technique to construct the layered perovskite thin films iwth well-defined thichness and uniformity by the Langmuir=Blodgett technique, and application of the film for cavity polariton laser usnig the Langmuir-Blodgett films.
ABSTRACT In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabrica... more ABSTRACT In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabricate disposable photodiodes as the detectors on the integrated lab-on-chip lasers. J-aggregated films of a cyanine dye, NK-1952 doped into a conductive polymer, poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) on the indium tin oxide (ITO) substrate have made by the ink-jet method, respectively. With the thin Al layer on the top of cyanine dye films as the cathode, while ITO substrate as the anode, the photodiodes have been demonstrated to be wavelength sensitive under the excitation of a tunable pico-second laser, which corresponds to the characteristic red-shifted, sharp and narrow J-aggregate absorption peak of each cyanine dye employed. The influence of ink-jet fabrication parameters, presence of metal ions and pH value of dye solutions on the J-aggregate formation and also the wavelength sensitivity of the photodiodes have been systematically investigated and the mechanisms involved have been discussed. It is found that by optimizing the ink-jet fabrication parameters such as UV exposure dose amount, and substrate temperature, or by introducing ions such as K+, Na+, or H+, the wavelength resolution of the ink-jet printed photodiodes can be improved significantly, and wavelength resolution of less than 0.1nm may be expected.
We report here two topics on the construction of organic/inorganic quantum-well materials based o... more We report here two topics on the construction of organic/inorganic quantum-well materials based on metal halide-based layer perovskite having an alternate layer structure consisting of an organic ammonium layer and a metal halide semiconductor layer. The first topic is the construction of new organic/inorganic quantum-well materials incorporated with functionalized ammonium molecules, which possess chromophores such as naphthalene and azobenzene, as
CLEO:2011 - Laser Applications to Photonic Applications, 2011
ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye fi... more ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye films. The radiation sensitivity and spectral resolution were improved significantly by approaches, indicating the realization of integrated flow-cytometry chips. OCIS codes: (230.5170) Photodiodes; (160.4890) Organic materials
ABSTRACT In order to obtain high performance Langmuir-Blodgett (LB) films, a closely packed monol... more ABSTRACT In order to obtain high performance Langmuir-Blodgett (LB) films, a closely packed monolayer of molecules having a suitable chromophore is required. However, a large chromophore sometimes interferes with close packing. We have been interested in amphiphiles having a heteroaromatic nucleus (H. Niino, K. Takehara, K. Isomura, H. Taniguchi, M. Era, T. Tsutsui and S. Saito, Chem. Lett., (1988) 785), with the hope of obtaining polarized built-up films. Here, we report that the mixing of two polar amphiphiles, having heterocycles which attract each other by electrostatic interaction, formed a closely packed stable monolayer which can be easily deposited into hetero Y-type LB-films.
A solution plasma (SP) process was employed to obtain hydrophilic graphene derivatives. Three dif... more A solution plasma (SP) process was employed to obtain hydrophilic graphene derivatives. Three different SP treatment time durations of 5, 10, and 15 min were applied as the experimental parameter to a sample solution including graphite in 9% hydrogen peroxide (H2O2) aqueous solution. The prepared graphene derivatives showed high dispersibility in contrast to that from natural graphite. The average particle size and absolute value of zeta potential of the obtained samples decreased as the SP treatment time increased. The particle size of SP-treated graphene derivatives in the supernatant linearly decreased depending on the SP treatment duration. The required particle size between 1.6 and 2.5 µm was obtained by SP treatment (i.e., reaction control was achieved). It was clearly shown that the necessary reaction time for graphene treatment using SP processing was much shorter than that by the modified Hummers method.
The distributed feedback plastic lasers for blue-violet were developed. The developed fluorene mo... more The distributed feedback plastic lasers for blue-violet were developed. The developed fluorene molecules for electroluminescence devices were adopted and doped in poly(methymethacrylate:2-hydroxyethylemethacrylate). Laser operation was confirmed at a wavelength of about 410 nm using frequency-tripled and passively Q-switched Nd:Cr:YAG laser. A laser threshold of 70 nJ and the longest lifetime of 3000 shots were demonstrated.
ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye fi... more ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye films. The radiation sensitivity and spectral resolution were improved significantly by approaches, indicating the realization of integrated flow-cytometry chips. OCIS codes: (230.5170) Photodiodes; (160.4890) Organic materials
This paper presents a novel approach for fabricating lead-based layered perovskite films. The per... more This paper presents a novel approach for fabricating lead-based layered perovskite films. The perovskite structure was formed during the transfer of a perovskite-unform monolayer onto a substrate. ...
Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenyleth... more Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, CaI2, CdI2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of PbI-based layered perovskite mixed with CaI-based layered perovskite (20 molar%) is about 5 times large that of the pristine PbI-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-b...
Lead-halide based layered perovskite compounds (RNH3)2PbX4 self-organize organic-inorganic superl... more Lead-halide based layered perovskite compounds (RNH3)2PbX4 self-organize organic-inorganic superlattice which two-dimensional inorganic semiconductor layer consisting of corner-sharing PbX6 octahedra and organic ammonium RNH3 layered are alternately piled up. Owing to the low dimensional semiconductor nature, they form stable exciton having large binding energy of several hundred meV and exhibit effcient exciton emission, electroluminescence and optical nonlinearity. In this report, we present optical properties of the layered perovskites and their application for EL device, improvement of exciton emission effciency by cation mixing for highly efficient emissive devices, and development of preparation technique to construct the layered perovskite thin films iwth well-defined thichness and uniformity by the Langmuir=Blodgett technique, and application of the film for cavity polariton laser usnig the Langmuir-Blodgett films.
ABSTRACT In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabrica... more ABSTRACT In this work, a drop-on-demand piezoelectric ink-jet system has been employed to fabricate disposable photodiodes as the detectors on the integrated lab-on-chip lasers. J-aggregated films of a cyanine dye, NK-1952 doped into a conductive polymer, poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) on the indium tin oxide (ITO) substrate have made by the ink-jet method, respectively. With the thin Al layer on the top of cyanine dye films as the cathode, while ITO substrate as the anode, the photodiodes have been demonstrated to be wavelength sensitive under the excitation of a tunable pico-second laser, which corresponds to the characteristic red-shifted, sharp and narrow J-aggregate absorption peak of each cyanine dye employed. The influence of ink-jet fabrication parameters, presence of metal ions and pH value of dye solutions on the J-aggregate formation and also the wavelength sensitivity of the photodiodes have been systematically investigated and the mechanisms involved have been discussed. It is found that by optimizing the ink-jet fabrication parameters such as UV exposure dose amount, and substrate temperature, or by introducing ions such as K+, Na+, or H+, the wavelength resolution of the ink-jet printed photodiodes can be improved significantly, and wavelength resolution of less than 0.1nm may be expected.
We report here two topics on the construction of organic/inorganic quantum-well materials based o... more We report here two topics on the construction of organic/inorganic quantum-well materials based on metal halide-based layer perovskite having an alternate layer structure consisting of an organic ammonium layer and a metal halide semiconductor layer. The first topic is the construction of new organic/inorganic quantum-well materials incorporated with functionalized ammonium molecules, which possess chromophores such as naphthalene and azobenzene, as
CLEO:2011 - Laser Applications to Photonic Applications, 2011
ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye fi... more ABSTRACT Organic photodiodes were made by ink-jet method based on the J-aggregated cyanine dye films. The radiation sensitivity and spectral resolution were improved significantly by approaches, indicating the realization of integrated flow-cytometry chips. OCIS codes: (230.5170) Photodiodes; (160.4890) Organic materials
ABSTRACT In order to obtain high performance Langmuir-Blodgett (LB) films, a closely packed monol... more ABSTRACT In order to obtain high performance Langmuir-Blodgett (LB) films, a closely packed monolayer of molecules having a suitable chromophore is required. However, a large chromophore sometimes interferes with close packing. We have been interested in amphiphiles having a heteroaromatic nucleus (H. Niino, K. Takehara, K. Isomura, H. Taniguchi, M. Era, T. Tsutsui and S. Saito, Chem. Lett., (1988) 785), with the hope of obtaining polarized built-up films. Here, we report that the mixing of two polar amphiphiles, having heterocycles which attract each other by electrostatic interaction, formed a closely packed stable monolayer which can be easily deposited into hetero Y-type LB-films.
A solution plasma (SP) process was employed to obtain hydrophilic graphene derivatives. Three dif... more A solution plasma (SP) process was employed to obtain hydrophilic graphene derivatives. Three different SP treatment time durations of 5, 10, and 15 min were applied as the experimental parameter to a sample solution including graphite in 9% hydrogen peroxide (H2O2) aqueous solution. The prepared graphene derivatives showed high dispersibility in contrast to that from natural graphite. The average particle size and absolute value of zeta potential of the obtained samples decreased as the SP treatment time increased. The particle size of SP-treated graphene derivatives in the supernatant linearly decreased depending on the SP treatment duration. The required particle size between 1.6 and 2.5 µm was obtained by SP treatment (i.e., reaction control was achieved). It was clearly shown that the necessary reaction time for graphene treatment using SP processing was much shorter than that by the modified Hummers method.
The distributed feedback plastic lasers for blue-violet were developed. The developed fluorene mo... more The distributed feedback plastic lasers for blue-violet were developed. The developed fluorene molecules for electroluminescence devices were adopted and doped in poly(methymethacrylate:2-hydroxyethylemethacrylate). Laser operation was confirmed at a wavelength of about 410 nm using frequency-tripled and passively Q-switched Nd:Cr:YAG laser. A laser threshold of 70 nJ and the longest lifetime of 3000 shots were demonstrated.
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