Nishi, Japan
Nishi, Japan

Time filter

Source Type

Inoue M.,44 Motooka | Inoue M.,Kyushu University | Matsushima T.,Kyushu University | Matsushima T.,Japan Science and Technology Agency | And 3 more authors.
Applied Physics Letters | Year: 2016

We demonstrate that ter(9,9′-spirobifluorene) (TSBF) doped in a host matrix layer of 4,4′-bis(carbazol-9-yl)biphenyl (CBP) shows a low amplified spontaneous emission (ASE) threshold (Eth = 1.0 μJ cm-2) and suppressed electroluminescence efficiency roll-off at high current densities (no roll-off up to 100 mA cm-2). One origin of the low ASE threshold is that the TSBF-doped CBP layer possesses a very large radiative decay constant (kr = 1.1 × 109s-1). Singlet-triplet annihilation is almost suppressed in the TSBF-doped CBP layer, which can be ascribed to the small overlap between the emission and triplet absorption of TSBF. Also, the small energy level difference between TSBF and CBP minimizes carrier trapping in TSBF, leading to the suppression of singlet-polaron annihilation. TSBF showed one of the lowest Eth and the most suppressed efficiency roll-off among organic laser dyes investigated in this study and, therefore, is believed to be a promising candidate to realize electrically pumped organic semiconductor laser diodes in the future. © 2016 AIP Publishing LLC.


Inoue M.,44 Motooka | Inoue M.,Kyushu University | Serevicius T.,Kyushu University | Serevicius T.,Vilnius University | And 11 more authors.
Chemical Physics Letters | Year: 2016

Electroluminescence efficiency roll-off in organic light-emitting diodes with thermally activated delayed fluorescence emitters 1,2-bis(carbazol-9-yl)-4,5-dicyanobenzene (2CzPN) and 3-(9,9-dimethylacridin-10(9H)-yl)-9H-xanthen-9-one (ACRXTN) is investigated by considering intramolecular exciton relaxation processes. Electroluminescence efficiency roll-off at high current density is dramatically suppressed using ACRXTN as an emitter instead of 2CzPN because of suppressed bimolecular exciton annihilation processes such as singlet-triplet and triplet-triplet annihilation. The rate constant of reverse intersystem crossing from triplet to singlet excited states of ACRXTN is about 300 times higher than that of 2CzPN, decreasing triplet exciton density and suppressing exciton annihilation processes under optical and electrical excitation. © 2015 Elsevier B.V. All rights reserved.


Inoue M.,44 Motooka | Inoue M.,Kyushu University | Matsushima T.,Kyushu University | Matsushima T.,Japan Science and Technology Agency | And 4 more authors.
Chemical Physics Letters | Year: 2015

Efficient introduction of oxygen into a solid-state organic film is demonstrated by applying a high oxygen pressure of 200 MPa to the film. The oxygen-introduced film shows strong suppression of singlet-triplet annihilation (STA) because triplet excitons are quenched by oxygen introduced inside the film. It is demonstrated that oxygen molecules are uniformly distributed in the film and that oxygen molecules are left in the film to some extent when the film is in a vacuum. The concentration of oxygen inside the film is calculated to be a very high value on the order of 4.4 × 1020 cm-3. © 2015 Elsevier B.V. All rights reserved.

Loading 44 Motooka collaborators
Loading 44 Motooka collaborators