Kyushu University · Engineering
Professor Atula S. D. Sandanayaka's research lab specializes in organic semiconductors, with a focus on developing high-performance optoelectronic materials and devices. Key research directions include the design and fabrication of organic lasers—particularly surface-emitting and distributed feedback lasers—using high-gain, low-loss organic semiconductors such as carbazole-based dyes. The lab also investigates charge transfer processes in mechanically interlocked molecules like rotaxanes, exploring their photoinduced electron transfer dynamics for potential applications in molecular electronics and artificial photosynthesis. Additionally, the group examines degradation mechanisms in organic light-emitting diodes to improve device stability and longevity.
Figures are computed from collected data and may differ slightly.
Abstract In this study, we investigate the lasing properties of 4,4′-bis[( N -carbazole)styryl]biphenyl thin films under electrical pumping. The electroluminescent devices incorporate a mixed-order distributed feedback SiO 2 grating into an organic light-emitting diode structure and emit blue lasing. The results provide an indication of lasing by direct injection of current into an organic thin film through selection of a high-gain organic semiconductor showing clear separation of the lasing wav
The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin fi
Degradation of organic light-emitting diodes (OLEDs) operated continuously at a constant current density is investigated using photoluminescence techniques. The OLEDs contained the thermally activated delayed fluorescence emitting dopant (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN). OLED degradation proceeds mainly on the basis of excited-state instability of host molecules rather than processes related to 4CzIPN. Additionally, the electrochemical instability of radical cati
Two rotaxanes tethering [60]fullerene (C60) and triphenylamine (TPA) moieties were synthesized in good yields by the urethane end-capping method using a crown ether−secondary amine motif. In these rotaxanes, the C60 group serving as electron acceptor is attached to the crown ether wheel through which the axle with a TPA group acting as electron donor on its terminal penetrates. One rotaxane has an ammonium moiety, whereas the other has a neutral amide moiety in the center of the axle. The corres
Quasi-continuous-wave surface-emitting lasing is realized in a device based on the organic laser dye 4,4′-bis[(N-carbazole)styryl]biphenyl and second-order grating under optical pulse excitation. A repetition rate of up to 8 MHz and a lasing threshold in the order of 0.25 μJ cm−2 are the highest and lowest ever reported among quasi-continuous-wave organic thin-film lasers. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such material
Photoinduced electron transfer in self-assembled (via ion-pairing) porphyrin−single-wall carbon nanotube (SWNT) donor−acceptor hybrids has been demonstrated. Toward this, first, SWNTs were solubilized by π−π stacking of pyrene (Pyr) functionalized with either a cationic (alkyl ammonium; Pyr-NH3+) or anionic (butyric acid; Pyr-COO−) terminal groups. The SWNT/Pyr-NH3+ and SWNT/Pyr-COO− hybrids thus obtained were subsequently used to generate donor−acceptor hybrids by ion-pairing with free-base or
Three rotaxanes, with axles with two zinc porphyrins (ZnPs) at both ends penetrating into a necklace pending a C60 moiety, were synthesized with varying interlocked structures and axle lengths. The intra-rotaxane photoinduced electron transfer processes between the spatially positioned C60 and ZnP in rotaxanes were investigated. Charge-separated (CS) states (ZnP*+, C60*-)rotaxane are formed via the excited singlet state of ZnP (1ZnP*) to the C60 moiety in solvents such as benzonitrile, THF, and
We demonstrate an ability to control the structures and photodynamics of porphyrin-based nanoassemblies via solvent mixture technique. Surfactants such as ethylene glycol (EG) derivatives with different chain lengths are employed to control the sizes and shapes of nanoparticles composed of meso-substituted tetracarboxyphenyl porphyrin [H2P(CO2H)4] in mixed H2O/THF solvent. With increasing the chain lengths, the diameters of H2P(CO2H)4/EG composite nanoparticles systematically increase in the ran
A new class of porphyrin nanorods structurally controlled by encapsulated fullerene derivatives is prepared via a solvent mixture technique. These nanorods, composed of fullerenes (C60, C60 derivatives and C70) and zinc meso-tetra(4-pyridyl)porphyrin [ZnP(Py)4], are formed with the aid of a surfactant, cetyltrimethylammonium bromide (CTAB), in a DMF/acetonitrile mixture. In scanning electron microscopy (SEM) measurement, ZnP(Py)4 pristine hexagonal nanotubes with a large hollow structure [denote
A non-covalent double-decker binding strategy is employed to construct functional supramolecular single-wall carbon nanotubes (SWCNT)-tetrapyrrole hybrids capable of undergoing photoinduced electron transfer and performing direct conversion of light into electricity. To accomplish this, two semiconducting SWCNTs of different diameters (6,5 and 7,6) were modified via π-π stacking of pyrene functionalized with an alkyl ammonium cation (PyrNH(3)(+)). Such modified nanotubes were subsequently assemb
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