Yusuke Wakikawa

Shizuoka Institute of Science and Technology

A triplet-triplet pair is a key intermediate in singlet fission (SF), which has the potential to overcome the theoretical limit of solar cell efficiency. Here, we report a new spectroscopy to directly detect a short-lived triplet-triplet pair via the effects of radio-wave (RF) irradiation near zero magnetic field at room temperature. The fluorescen...

Ultrasonic cavitation in organic solvents remains poorly understood in contrast with aqueous systems, largely because of complexities related to solvent decomposition. In this study, we sonicated different types of organic solvents (i.e. linear alkanes, aliphatic alcohols, aromatic alcohols, and acetate esters) under argon saturation. The average t...

To achieve high-speed machining of sintered carbide, a new process of milling using an electrochemical reaction is proposed. In this report, the principle of this method and its effectiveness were confirmed. First, the phenomena on the sintered carbide surface occurring in the electrochemical reaction were investigated. The reactions that could occ...

Using electrically and capacitively detected magnetic resonances (EDMR and CDMR) techniques, we clarified recombination in regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) films, which is an important elementary process for photoconduction. The modulation frequency dependences of the EDMR and CDMR reveal the coexistence of two types of electron–...

Chitin, which is the polymer of N-acetylglucosamine (GlcNAc) linked by β1,4 glycoside bonds, has been reported as a soil amendment to mitigate plant soil diseases, increasing the population of chitin-degrading bacteria, and chitinolytic enzymatic activity in the soil. In some chitin-degrading bacteria, whose chitinolytic systems have been intensive...

To achieve high-speed machining of sintered carbide, a new process of milling using an electrochemical reaction is proposed. First, the phenomena on the sintered carbide surface occurring in the electrochemical reaction were investigated. The reactions that could occur on the sintered carbide surface are the elution of Co, the oxidation of Co, and...

The magnetoconductance (MC) effect was investigated for two types of organic solar cells with single junction (SJ) and bulk junction (BJ) of poly(3-hexylthiophene) (P3HT) as donor (D) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as acceptor (A). Three components with different half-field-at-half-maximums (B1/2) of 4 ± 1, 20 ± 15 and >400 m...

Temperature dependencies of transient photocharge and magnetophotoconductance effect of columnar self-assemblies of the hexabenzocoronene derivative (HBC-C14), which is a prospective one-dimensional photoconductor, presented different thermal activation processes for carrier generation and transportation, respectively. Thermal equilibrium between t...

The effect of the solvent viscosity dependence of time-resolved magnetoluminescence (ML) on the delayed fluorescence of 9,10-diphenylanthracene (DPA) sensitized by platinum octaethylporphyrin has clarified the structure and dynamics of the triplet-triplet pair (TT), i.e., the transition state of triplet fusion. Phase inversion of the ML effect with...

Magnetic field effects (MFEs) on singlet fission were studied by observing fluorescence from organic crystal of 1,6-diphenyl-1,3,5-hexatriene under magnetic fields of up to 5 T. We found anomalous MFE dips at magnetic fields higher than 2 T, in addition to the known MFEs which saturated around 1 T. The observed results were analyzed by using the st...

The spin sublevel dynamics of the excited triplet state in thermally activated delayed fluorescence (TADF) molecules have not been investigated for high-intensity organic light-emitting diode materials. Understanding the mechanism for intersystem crossing (ISC) is thus important for designing novel TADF materials. We report the first study on the I...

We demonstrate the magnetoconductance (MC) effect originated from depressing the spin mixing in encounter pairs under the external magnetic field provides quantitative information about the singlet fission, the charge recombination, and the trap-related dynamics with triplet exciton in a bilayer device of pentacene (Pen) and fullerene (C60). Three...

By transient photoconductance under an external magnetic field (Magnetophotoconductance, MPC), we have investigated photocarrier dynamics in hexabenzocoronene (HBC) self-assemblies and [6, 6]-phenyl C 61 butyric acid methyl ester (PCBM) films. It was clarified that the lamination of electron acceptor layer on the surfaces of HBC nanotubular self-as...

The thermal annealing effects on the photocarrier dynamics in thin films of [6,6]-phenyl C-61 butyric acid methyl ester (PCBM) on quartz substrates are investigated. Both the photocarrier generation via charge-transfer state and the charge transport in PCBM films are studied by time-resolved photoconductance (PC) measurement. More than 90% of exter...

Measurements of transient photoconductance under an external magnetic field were used to investigate photocarrier dynamics in low-dimensional hexabenzocoronene (HBC) self-assemblies, which are a promising material group for highly efficient solar cells achieved by bottom-up technology, and to clarify the effect of lamination with electron acceptor...

Extremely long nanofibers, whose lengths reach the millimeter regime, are generated via co-aggregation of a melamine-appended perylene bisimide semiconductor and a substituted cyanurate, both of which are ditopic triple-hydrogen-bonding building blocks; they co-aggregate in an unexpected stoichiometrically mismatched 1:2 ratio. Various microscopic...

By means of the integral mode time-of-flight measurement of the drift motion of the photoinjected charge at room temperature, we observed magnetic field effect (MFE) on the photocharge in self-assembled nanotube of hexabenzocoronene (HBC) at the configurations where the magnetic field is parallel and perpendicular to the electric field. The detecte...

An amorphous molecular semiconductor, poly(N-vinylcarbazole) (PVCz), exhibits negative giant magnetoresistance (MR) under ambient conditions. The application of a weak magnetic field of 10mT to PVCz films doped with lumichrome, in which light excitation immediately creates triplet electron-hole (e-h) pairs that are precursors of photocarriers, caus...