Search results for: Toshimitsu Mochizuki

Items from 1 to 14 out of 14 results

article

Effects of different particle-sized Al pastes on rear local contact formation and cell performance in passivated emitter rear cells

Supawan Joonwichien, Toshimitsu Mochizuki, Katsuhiko Shirasawa, Hidetaka Takato

Energy Procedia > 2017 > 124 > C > 412-417

This work presents the effects of different Al pastes on the rear contact formation in passivated emitter rear cells (PERC) after firing as well as the impact on cell performance. In this study, the rear side of PERC cells was metalized with two different PERC Al pastes—one consisting of fine particles, and another consisting of coarse particles. Our results found that the open-circuit voltages (V...

chapter

Evaluation of Si-SiO_x interface using laser terahertz emission microscope (LTEM)

Toshimitsu Mochizuki, Akira Ito, Hidetoshi Nakanishi, Katsuto Tanahashi, more

2016 Conference on Lasers and Electro-Optics (CLEO) > 1 - 2

2016 Conference on Lasers and Electro-Optics (CLEO)

Terahertz emission from a Si metal-oxide-semiconductor (MOS) structure with transparent indium tin oxide electrodes was measured using a Laser Terahertz Emission Microscope (LTEM) with time-domain spectroscopy technique. The THz waveform and amplitude at various external voltage were compared with the capacitance-voltage characteristics. The observed peak amplitude strongly correlated with the surface...

chapter

A “smart stack” triple-junction cell consisting of InGaP/GaAs and crystalline Si

Hidenori Mizuno, Kikuo Makita, Takeshi Tayagaki, Toshimitsu Mochizuki, more

2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC) > 1923 - 1925

2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)

Smart stack is a handy method to construct multi-junction tandem through the interconnection of different types of solar cells using a Pd nanoparticle array as a bonding mediator. In this study, a triple-junction cell was fabricated from InGaP/GaAs and crystalline Si subcells using the smart stack method, which resulted in a conversion efficiency of 23.2%. The EQE analysis of the smart stack cell...

chapter

Current leakage and fill factor in multi-junction solar cells linked via absolute electroluminescence characterization

Lin Zhu, Masahiro Yoshita, Tetsuya Nakamura, Toshimitsu Mochizuki, more

2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC) > 1239 - 1243

2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)

Direct link between current-leakage features and fill factors was demonstrated in GaInP/GaAs 2-junction solar cells via combining measurements of absolute electroluminescence (EL) intensity and EL imaging. The drops of subcell external radiative efficiency under low injection level have shown large differences among the solar cells fabricated in the same batch, which lead to the difference in the...

article

Characterizations of Radiation Damage in Multijunction Solar Cells Focused on Subcell Internal Luminescence Quantum Yields via Absolute Electroluminescence Measurements

Lin Zhu, Masahiro Yoshita, Shaoqiang Chen, Tetsuya Nakamura, more

IEEE Journal of Photovoltaics > 2016 > 6 > 3 > 777 - 782

Via absolute electroluminescence measurements, we characterized degradations of internal luminescence quantum yield or internal radiative efficiency (

$\eta _{{\rm int}i}$

) in respective subcells in GaInP/GaAs/Ge triple-junction and GaInP/GaAs double-junction solar cells after irradiations of protons and electrons with different energy and fluence (

$\phi$

). Compared with typical open-circuit-voltage...

article

Effect of very high magnetic field on the optical properties of firefly light emitter oxyluciferin

Weihang Zhou, Daisuke Nakamura, Yu Wang, Toshimitsu Mochizuki, more

Journal of Luminescence > 2015 > 165 > C > 15-18

Magnetic field effect on enzymatic reactions is under intensive study in the past decades. Recently, it was reported that firefly bioluminescence was suppressed and red-shifted significantly when exposed to external magnetic field. However in this work, by means of selective excitation, we confirmed that emission properties of firefly light emitter “oxyluciferin” are completely immune to external...

chapter

Absolute electroluminescence imaging of multi-junction solar cells and calibration standards

Masahiro Yoshita, Lin Zhu, Changsu Kim, Hidefumi Akiyama, more

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC) > 1 - 4

2015 IEEE 42nd Photovoltaic Specialists Conference (PVSC)

We developed absolute electroluminescence (EL) calibration standards to evaluate absolute radiative-emission rates from subcells in multi-junction (MJ) solar cells. The absolute-EL-measurement system consists of an EL imaging setup and an emission-intensity-calibrated planar light-emitting diode with a circular open aperture as an emission-intensity standard. We applied this system to the measurements...

chapter

Characterizations of radiation damages in multi-junction solar cells focused on subcell internal luminescence quantum yields via absolute electroluminescence measurements

Lin Zhu, Masahiro Yoshita, Shaoqiang Chen, Tetsuya Nakamura, more

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC) > 1 - 4

2015 IEEE 42nd Photovoltaic Specialists Conference (PVSC)

Via absolute electroluminescence (EL) measurements, we characterized degradations of internal luminescence quantum yields in respective subcells in GaInP/GaAs/Ge triple-junction solar cells after radiation damages by proton irradiations with different energy and fluence. Compared with typical open-circuit-voltage characterizations, the internal luminescence quantum yield turned out to be a sensitive,...

article

Analysis of Oxyluciferin Photoluminescence Pathways in Aqueous Solutions

Miyabi Hiyama, Toshimitsu Mochizuki, Hidefumi Akiyama, Nobuaki Koga

Photochemistry and Photobiology > 91 > 1 > 74 - 83

We evaluated the pK_a values of oxyluciferin and its conjugate acids and bases theoretically with the help of experimental correction values, from which free energies for the first excited and the ground states of all the species were estimated. On the basis of these results, we calculated pH‐dependent absorption spectra, where the relative absorption intensities of various species strongly depend...

article

Analysis of Photoexcitation Energy Dependence in the Photoluminescence of Firefly Luciferin

Miyabi Hiyama, Hidefumi Akiyama, Toshimitsu Mochizuki, Kenta Yamada, more

Photochemistry and Photobiology > 90 > 4 > 820 - 828

The whole pathways for photoluminescence, which include absorption, relaxation and emission, of firefly luciferin in aqueous solutions of different pH values with different photoexcitation energies were theoretically investigated by considering protonation/deprotonation. It is experimentally known that the color of fluorescence changes from green to red with a decrease in the photoexcitation energy...

chapter

Conversion efficiency limits and optimized designs for tandem solar cells with realistic sub-cell material quality

Lin Zhu, Toshimitsu Mochizuki, Masahiro Yoshita, Shaoqiang Chen, more

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC) > 3404 - 3408

2014 IEEE 40th Photovoltaic Specialists Conference (PVSC)

To examine practical efficiency limits of tandem solar cells, we calculated conversion efficiency (η_sc) and optimized sub-cell band-gap energies (E_g) in 1-, 2-, 3-, 4-, and 5-junction cells via a detailed-balance theory, taking account of the realistic internal luminescence quantum yields (y_int) of the sub-cell materials. We found that η_sc drastically decreases as the geometric mean y_int* of all sub-cells'...

chapter

Balance sheets of energy and carriers and subcell characteristics in a GaInP/GaAs/Ge tandem solar cell

Shaoqiang Chen, Lin Zhu, Masahiro Yoshita, Toshimitsu Mochizuki, more

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC) > 1780 - 1783

2014 IEEE 40th Photovoltaic Specialists Conference (PVSC)

We developed a straightforward and potentially standard method of accessing the balance sheets of energy and carriers as well as respective subcell photovoltaic properties in multi-junction tandem solar cells by measuring absolute electroluminescence quantum yields. This method was indeed applied to a GaInP/GaAs/Ge 3-junction solar cell for satellite use. The 28.7% efficiency derived as a sum of 15...

article

Electroluminescence of GaNAs/GaAs MQWs p–i–n junctions grown by RF-MBE using modulated nitrogen radical beam source

Natsumi Ohta, Kohei Arimoto, Masahiro Shiraga, Kenta Ishii, more

Journal of Crystal Growth > 2013 > 378 > Complete > 150-153

We have investigated the electrical and optical properties of p–i–n junction structures in which un-doped GaNAs/GaAs multiple quantum wells (MQWs) were sandwiched by p- and n-doped GaAs layers. The samples were formed on the GaAs (001) substrates by plasma assisted molecular beam epitaxy (RF-MBE) using the modulated N radical beam method. We have prepared several samples for various GaNAs MQW structures...

article

Observation of the quantum Hall effect in cleaved InAs surfaces

Yukihide Tsuji, Toshimitsu Mochizuki, Tohru Okamoto

Physica E: Low-dimensional Systems and Nanostructures > 2006 > 34 > 1-2 > 156-159

We have performed the in-plane magnetotransport measurements on the two-dimensional electron gas at the cleaved p-InAs (110) surface by deposition of Ag. The surface electron density Ns is determined from the Hall coefficient at 1.5K. The coverage dependence of Ns is well explained by the assumption that each adsorbed Ag atom denotes one electron into InAs until the surface Fermi level reaches the...

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