Kazuhiro Manseki

Mg-doped TiO2 nanorods improving open-circuit voltages of ammonium lead halide perovskite solar cells

Mg-doped TiO2 nanorods were successfully synthesized from colloidal titanate by a microwave hydrothermal reaction. Use of such TiO2 having an elevated conduction band edge as an electron extracting material for ammonium lead halide perovskite solar cells resulted in an increase of Voc by as much as 215 mV.

Microwave synthesis of size-controllable SnO2 nanocrystals for dye-sensitized solar cells

A microwave hydrothermal synthesis of size-tunable SnO2 nanocrystals is achieved by employing a SnCl4 solution in a mixed ethanol–water solvent. A large increase in ethanol content to over 90%, as well as an increase in SnCl4 concentration, is the key to successfully obtain highly crystallized and well dispersed SnO2 particles as large as 26 nm, which can be determined by XRD and HR-TEM observations. Such well ripened SnO2 crystals exhibit a good performance as photoelectrodes in dye-sensitized solar cells, resulting in an IPCE of around 70% when N719 dye is employed. The size dependent differences in photoelectrochemical properties are studied by SLIM-PCV measurements. The results indicate that fast electron transport occurs with the large SnO2 crystals, owing to their low electron trap density and shallow distribution.

Size-controlled synthesis of anisotropic TiO2 single nanocrystals using microwave irradiation and their application for dye-sensitized solar cells

A microwave hydrothermal reaction of colloidal titanates is presented as a cost-effective synthesis to produce TiO(2) single nanocrystals. The photoelectrode consisting of anisotropic nanorods and V-shaped twins has a significant advantage for achieving an appreciable incident photon-to-current conversion efficiency of 85.6% for the dye-sensitized solar cell.

Long-term stability of novel double rhodanine indoline dyes having one and two anchor carboxyl group(s) in dye-sensitized solar cells

An indoline dye having both α-cyanoacrylic acid and rhodanine acetic acid anchor groups at the acceptor moiety exhibited improved stability under fluorescence light irradiation.

Evaluation of a metal free dye for efficient dye sensitized solar cells based on hydrothermally synthesized TiO2 nanoflowers

The main aim of the present investigation is to evaluate dye sensitized solar cells (DSSCs) properties of hydrothermally synthesized 3D TiO2 nanoflowers based on DN350 organic dye. The dye loading time has been optimized from the current–voltage (J–V) characteristics in order to obtain high performance DSSCs. Further TiCl4 surface treatment was conducted for effective dye loading and fast electron transport for the improvement of DSSC performance. The dye loading and its performance evaluation has been optimized and analysed using J–V performance, UV-vis spectroscopy and incident-photon-to-electron conversion efficiency (IPCE) etc. characterization techniques. The diffusion coefficient, diffusion length and electron life time have be evaluated using intensity-modulated photocurrent and photovoltage experiments (IMPS/IMVS). Our optimized results show that 30 min TiCl4 treated TNF samples exhibit current density (JSC) = 14.70 mA cm−2, open circuit voltage (VOC) = 0.650 V, Fill Factor (FF) = 0.62 and power conversion efficiency (PCE) = 5.92%.

Wide-Range Near-Infrared Sensitizing 1H-Benzo[c,d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells

NIR absorbing squaraine dyes SQ1-SQ7 having 1 H-benzo[ c, d]indol-2-ylidene as a donor moiety were designed for application in DSSCs. Annulation of the benzene ring to an 3 H-indolium-based anchor moiety led to a red-shifted and broadened absorption band on TiO2 film, which were reflected in the improved short-circuit current density of SQ2 (6.22 mA cm-2) compared to the nonbenzene fused derivative SQ1 (4.39 mA cm-2). Although the introduction of a butoxy (SQ4: 806 nm) or dialkylamino group (SQ5-SQ7: 815-820 nm) to the 1 H-benzo[ c, d]indol-2-ylidene-based donor moiety resulted in red-shifted absorption maxima in ethanol compared to the nonsubstituted derivative SQ2 (784 nm), the HOMO energy level of SQ4-SQ7 gave rise to an undesirable approximation to the redox potential of I-/I3-. Thus, the butoxy (SQ4: 0.56) and dialkylamino (SQ5-SQ7: 0.25-0.30) derivatives had relatively lower conversion efficiencies. Since the 2-ethylhexyl derivative SQ3 exhibited red-shifted absorption (λmax: 796 nm), suitable HOMO and LUMO energy levels, and relatively efficient restriction of charge recombination, this dye achieved the highest conversion efficiency (1.31%), along with a high IPCE response of over 20% over a wide range from 640 to 860 nm and an onset of IPCE at 1000 nm.

Structure identification of Ti(IV) clusters in low-temperature TiO2 crystallization: creating high-surface area brush-shaped rutile TiO2

We demonstrate for the first time a controlled reaction of Cl-coordinating Ti(IV) clusters in low-temperature hydrolysis (27 °C) to create large-surface area rutile TiO2 crystals. Trinuclear Ti(IV) cluster species were produced by the partial hydrolysis of an amorphous TiO2 derived from TiCl4. The structurally optimized cluster had a pseudo-cubane structure with edge-shared Ti(IV) octahedra exhibiting unique stacked electron density units. It is postulated that breaking of Ti–OH bonds in the cluster and the intermolecular assembly of the clusters during further polycondensation reactions resulted in the formation of corner-shared Ti(IV) octahedra. The controlled stability of the Ti(IV) clusters owing to reaction solvents enables the creation of rutile TiO2 crystals with intertwined brush-shaped TiO2 single crystal domains, with a large surface area of up to 201 m2 g−1. Understanding low-temperature reactions of transition-metal cluster intermediates would benefit the design criteria of many transition-metal oxide crystals for versatile applications.