Taro Toyoda

Bio: Taro Toyoda is an academic researcher from University of Electro-Communications. The author has contributed to research in topics: Quantum dot & Photoacoustic spectroscopy. The author has an hindex of 31, co-authored 175 publications receiving 4200 citations. Previous affiliations of Taro Toyoda include Kyushu Institute of Technology.

CH3NH3SnxPb(1-x)I3 Perovskite Solar Cells Covering up to 1060 nm.

Abstract: We report photovoltaic performances of all-solid state Sn/Pb halide-based perovskite solar cells. The cell has the following composition: F-doped SnO2 layered glass/compact titania layer/porous titania layer/CH3NH3SnxPb(1–x)I3/regioregular poly(3-hexylthiophene-2,5-diyl). Sn halide perovskite itself did not show photovoltaic properties. Photovoltaic properties were observed when PbI2 was added in SnI2. The best performance was obtained by using CH3NH3Sn0.5Pb0.5I3 perovskite. 4.18% efficiency with open circuit voltage 0.42 V, fill factor 0.50, and short circuit current 20.04 mA/cm2 are reported. The edge of the incident photon to current efficiency curve reached 1060 nm, which was 260 nm red-shifted compared with that of CH3NH3PbI3 perovskite solar cells.

High efficiency of CdSe quantum-dot-sensitized TiO2 inverse opal solar cells

Abstract: The authors have demonstrated an approach to sensitized-type solar cells, based on TiO2 inverse opal and the use of CdSe quantum dots (QDs) as sensitizers. CdSe QDs were grown in situ on TiO2 inverse opal electrodes, utilizing a chemical bath deposition method. All of the photovoltaic performances, including short circuit photocurrent density, open circuit voltage, fill factor, and efficiency, were significantly improved by surface modification with ZnS and fluoride ions. A power conversion efficiency of about 2.7% has been attained, under solar illumination of 100mW∕cm2. This value is relatively high for metal oxide solar cells, sensitized with semiconductor QDs.

Highly efficient CdS/CdSe-sensitized solar cells controlled by the structural properties of compact porous TiO2 photoelectrodes

Abstract: At present, the photovoltaic performance of quantum dot-sensitized solar cells (QDSCs) is still much lower than conventional DSCs. Appropriate porous TiO2 photoanodes for QDSCs need to be further investigated, and optimization of the nanoparticle-based photoanodes is highly desirable as well. In this article, the influence of the structural properties of various TiO2 photoanodes on CdS/CdSe-sensitized solar cells have been systematically studied. Quantitative analyses of light-harvesting efficiency (LHE) and electron-transfer yield (ΦET) for the QDSCs are investigated for the first time. It is revealed that the LHE increases in the long wavelength region with the addition of large size TiO2 particles to the transparent film. In the meantime, the balance between the light scattering and surface area also needs to be controlled, which can significantly restrain the dark current of the device. A double-layer photoanodic structure can give 4.92% of light-to-electricity conversion efficiency with a photoactive area of 0.15 cm2.

All-Solid Perovskite Solar Cells with HOCO-R-NH3+I– Anchor-Group Inserted between Porous Titania and Perovskite

Abstract: HOCO-R-NH3+I monolayer working as an anchor for perovskite (CH3NH3PbI3 (abbreviation: PEROVI3)) was inserted between the surface of porous metal oxide (titania or alumina) and the PEROVI3. Power conversion efficiency (PCE) of PEROVI3 solar cells increased from 8% to 10% after the HOCO-R-NH3+I– monolayer was inserted. Moreover, PCE of 12% was achieved for cells fabricated at optimized conditions. This increase in the efficiency was explained by retardation of charge recombination, and better PEROVI3 crystal growth, which improves PEROVI3 network on these porous metal oxides. It was proved that PEROVI3 crystal growth can be controlled by HOCO-R-NH3+I– on these porous metal oxides.

Suppression of Charge Carrier Recombination in Lead-Free Tin Halide Perovskite via Lewis Base Post-treatment.

Abstract: Lead-free tin perovskite solar cells (PSCs) show the most promise to replace the more toxic lead-based perovskite solar cells. However, the efficiency is significantly less than that of lead-based PSCs as a result of low open-circuit voltage. This is due to the tendency of Sn2+ to oxidize into Sn4+ in the presence of air together with the formation of defects and traps caused by the fast crystallization of tin perovskite materials. Here, post-treatment of the tin perovskite layer with edamine Lewis base to suppress the recombination reaction in tin halide PSCs results in efficiencies higher than 10%, which is the highest reported efficiency to date for pure tin halide PSCs. The X-ray photoelectron spectroscopy data suggest that the recombination reaction originates from the nonstoichiometric Sn:I ratio rather than the Sn4+:Sn2+ ratio. The amine group in edamine bonded the undercoordinated tin, passivating the dangling bonds and defects, resulting in suppressed charge carrier recombination.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells

Abstract: Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.

Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency

Abstract: Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and ∼18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.