We propose an emitting assist (EA) dopant system for obtaining organic light-emitting diodes (OLEDs) with pure red emission. The EA dopant (rubrene) did not itself emit but assisted the energy transfer from the host (Alq3) to the red emitting dopant (DCM2). The cell structure used was {indium tin oxide/hole injection layer [(20 nm), CuPc/hole transport layer (50 nm), NPB/emitting layer (40 nm), Alq3+DCM2 (2%)+rubrene (5 wt %)]/MgIn}. (CuPc: Copper (II) phthalocyanine, NPB: N, N′-Di(naphthalen-1-yl)-N, N′-diphenyl-benzidine, DCM2: 4-Dicyanomethylene- 2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-8-yl)vinyl]-4H-pyran). A stable red emission (chromaticity coordinates: x=0.64, y=0.36) was obtained in this cell within the luminance range of 100–4000 cd/m2. When the cell was not doped with rubrene, the emission color changed from red to orange as the luminance increased. The EA dopant system is a promising method for obtaining red OLEDs.

We report here a novel phenomenon: selective metal deposition on photoswitchable diarylethene (DAE) surfaces. Magnesium vapor was deposited by vacuum evaporation on the colored DAE but not on the uncolored surface. The selective deposition originates in the change of the glass transition temperature of the amorphous DAE film resulting from photoisomerization and therefore from changes of surface molecular motion. We clarified that Mg atoms on the uncolored surface actively migrated on the surface and were desorbed from the surface. The possibility of depositing other metals is also discussed. Light-controllable metal-integrated deposition was demonstrated as a new function of the photoswitchable molecular surfaces. This study reveals new features of the photoswitchable molecular surfaces, and their potential suggests bright prospects for future applications in organic electronics.

A principle of organic memory device using a bistable photochromic molecule is presented that allows extremely high bit densities and very low power consumption. This device is based on an isomerization reaction of photochromic diarylethene molecule via its excited state by an electric carrier injection, not by photon absorption. Experimental data show that the reversible writing and nondestructive reading of information by the carrier injection is feasible. The advantages and properties of such an organic semiconductor memory using a bistable molecule are discussed.

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Conventional solution electrochemiluminescent (SECL) cells have a low luminance. In this paper, we propose an ion conductive assistant dopant (ICAD) system to improve the luminance of SECL cells. The SECL cell is assumed to have a simple structure of [transparent electrode/emitting solution/transparent electrode]. The solution of the cell consists of a mixed solvent (o-dichlorobenzene/acetonitrile=2/1 (vol/vol)), rubrene used as the emitting material, and 1,2-diphenoxyethane used as the ICAD. When voltage is applied to this SECL cell, the cell achieves a luminance of 183 cd/m2 and a luminous efficiency of 1.5 cd/A at 8 V with yellow emission. On the other hand, an SECL cell without an ICAD results in a low luminance of 0.3 cd/m2 at 8 V, corresponding to a conventional SECL cell. The ICAD improves the luminance 600 times by enhancing the ion conduction of rubrene cations in the solution. Furthermore, when the mixed solvent (o-dichlorobenzene/toluene=2/1 (vol/vol)), which has a high voltage resistance, is used in the SECL cell, the cell obtains a maximum luminance of 986 cd/m2 at 80 V. The features of the SECL cell are a simple cell structure and a transparent emitting area. SECL cells are expected to be used in unique displays with a see-through function for automobiles, windows, information equipment, and so on.

We proposed and demonstrated a nondestructive readout method using photocurrent detection for photon-mode photochromic memory. The principle of this readout method, which utilized the ionization potential change according to photoisomerzation reaction, was confirmed by using a medium with a photochromic diarylethene layer and phthalocyanine photoabsorbing layer, and by using a near-infrared readout light. We demonstrated perfect nondestructive readout operations over 106 times.

A superhydrophobic surface on which the contact angle of a water droplet exceeds 170° was reversibly produced by alternate irradiation with UV and visible light. Superhydrophobicity is due to the formation of densely generated submicrometer sized needle-shaped crystals (less than 0.2-0.3 μm diameter and 2.2-2.5 μm long) at 30 °C, which is much lower than the eutectic temperature of either isomers of the diarylethene. Below the eutectic temperature, the generated crystals were much smaller than those generated above the eutectic temperature. These smaller crystals more effectively enhanced the superhydrophobicity.