Electrical investigation of the interface band structure in rubrene single-crystal/nickel junction

The electronic structure of the interface between rubrene (C42H28) single crystal and ferromagnetic Ni is studied using an electrical method from a viewpoint of spintronics applications of organic single crystals. The Schottky barrier height at the interface is estimated to be 0.56 eV, and our finding is compared with previous results in spectroscopic method. This study clarifies the importance of electrical investigations of the Schottky barriers for various ferromagnet/organic systems and suggests that functionalization and carrier doping to rubrene single crystals are potential for obtaining the thinner barriers and yielding conclusive electrical spin injection

Electron transport in rubrene single-crystal transistors

We report a study of impurity effects on the electron transport of rubrene single crystals. A significant improvement of electron carrier mobility up to 0.81 cm(2)/V s is achieved by performing multiple purifications of single crystals and device aging inside an N(2)-filled glove box. The hole/electron mobility ratio obtained is in good agreement with the reported theoretical calculation, suggesting that the intrinsic electron transport of organic semiconductors is also exploitable in a manner similar to that of hole transport

Metallic phase in the metal-intercalated higher fullerene Rb8.8(7)C84

A new material of higher fullerene, RbxC84, was synthesized by intercalating Rb metal into C-84 crystals. The RbxC(84) crystals showed a simple cubic (sc) structure with lattice constant, a, of 16.82 (2) angstrom at 6.5 K, and 16.87 (2) angstrom at 295 K. The Rietveld refinements were achieved with the space group, Pa (3) over bar, based on a model that the C-2 axis of D2d-C84 aligned along [111]. The sample composition was determined to be Rb-8.8(7) C-84. The ESR spectrum at 303 K was composed of a broad peak with peak-to-peak linewidth Delta H-pp of 220 G, and a narrow peak with Delta H-pp of 24 G. Temperature dependence of the broad peak clearly showed a metallic behavior. The metallic behavior was discussed based on a theoretical calculation. This finding of new metallic phase in a higher fullerene is the first step for a development of new types of fullerene materials with novel physical properties such as superconductivity.</p

High current densities in a highly photoluminescent organic single-crystal light-emitting transistor

We report the improvement of electron transport in 5,5'-bis(biphenylyl)-2,2':5',2 ''-terthiophene (BP3T) single crystals on a field-effect transistor configuration by systematically investigating the effects of device aging under pure nitrogen and optimizing the organic dielectric layer-fabrication process. We reduced the effect of electron traps and achieved extremely high current densities up to 10 kA/cm(2), which is one or two orders of magnitude greater than the current densities achieved in previous devices

Green light emission from the edges of organic single-crystal transistors

We have fabricated ambipolar light-emitting field-effect transistors made of 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5) single crystals, which have 35% fluorescent quantum efficiency. The obtained hole and electron mobilities were 2.9 x 10(-1) cm(2)/V s and 6.7 x 10(-3) cm(2)/V s, respectively. These are the highest values among AC5 transistors. Importantly, although the light emission from the crystal surface was less than the detection level of the camera, we observed bright and polarized light emission from the edge of the single crystals. This polarized edge emission is attributed to the strong self-assembled light-confining nature and perfectly aligned transition dipole moments, which are advantageous for future laser devices