We have demonstrated improvement in the efficiency of TDAPB-based OLEDs. The external quantum efficiency of 8.2% and a power efficiency of 17.3 lm/W were achieved. The results suggest that using the starburst small-molecule TDAPB allows for easy fabrication and is effective for achieving high efficiencies in simple device structures.

The effects of the gate dielectrics on ambipolar transport in top-gate-type polymer light-emitting transistors with single-layer and bilayer gate dielectrics are investigated. Hole field-effect mobility is dependent on the dielectric constant of the gate dielectric onto the active layer. Hole transport of devices is affected by the dipolar disorder in the first gate dielectric layer on the active layer. Electron threshold voltage tends to decrease with increasing the total stacked gate capacitance.

Organic field-effect transistors (OFETs) based on a composite with the same thiophene backbone were fabricated by spin coating using an annealing solution of poly(3-hexylthiophene) (PAT6) and α, ω-dihexylsexithiophene (DH-6T). The morphology of grains on the non-octadecyltrichlorosilane (OTS) treated and OTS treated gate insulators is granular and tube-like, respectively. The different morphologies of the OFETs with non-OTS treated and OTS-treated gate insulators result in the improvement of field-effect mobility. In the case of poly(ethylene naphthalate) substrate, an OFET with an 89 wt% DH-6T composite corresponding to two molecules of DH-6T per hexylthiophene repeating unit had a carrier mobility of 0.019 cm2/Vs.

The optical pulses of 50 MHz has been obtained from an organic light emitting diode (OLED) based on the Alq3 emissive layer with the active area of 0.01 mm2. We demonstrate that the OLEDs can be applied to fields of optical communication as the electro-optical conversion device for transmitting the signals of moving picture.

We investigated luminescent properties in combination of red emissive europium complex of tris(dibenzoylmethane)-mono(4,7-dimethylphenanthroline)europium(III) [Eu(dbm)3phen] and blue phosphorescent molecule of bis[(4,6-difluorophenyl)-pyridinato-N,C2'] (picolinate) iridium (III) (FIrpic) doped in poly(N-vinyl-carbazole) (PVK). A sharp red emission from Eu(dbm)3phen was observed in photoluminescence (PL) measurement, whereas, in the case of electroluminescence (EL), emission from FIrpic and Eu compound were observed. The difference of the PL and EL spectra indicates that different energy transfer processes between Eu(dbm)3phen and FIrpic are suggested.

The characteristics of violet-sensitive organic photodetectors (OPDs) utilizing polyalkylfluorene and triplet materials have been studied as a host and a dopant material, respectively. For the photo absorption layer, poly(9,9-dioctylfluorene) [PFO] and a phosphorescent iridium complex (Iridium (III) bis(2-(4,6-difluorophenyl)pyridinato-N,C2) [FIrpic] or Iridium (III) bis(2-(2'-benzothienyl)pyridinato-N,C3')(acetyl-acetonate) [(btp)2Ir(acac)]) were used as a host and a dopant material, respectively. PFO: (btp)2Ir(acac) device showed less photocurrent than PFO device because (btp)2Ir(acac) enhances recombination of the photo generated carriers in the photo absorption layer. On the other hand, PFO : FIrpic device showed larger photocurrent than PFO device due to triplet energy transfer from FIrpic to PFO. A cutoff frequency of 20 MHz was observed using a sinusoidal modulated violet laser light illumination under the reverse bias of 8 V.

High luminance and high speed response with the cut-off frequency of more than 50 MHz in multilayer polyfluorene-based light-emitting diodes with an interlayer were achieved. We realized multilayer polyfluorene-based light-emitting diodes for frequency response up to 100 MHz.

The luminance of about 10,000 cd/m2 at an applied voltage of 9.2 V and the external emission efficiency 5.5 cd/A at an injection current density of 50 mA/cm2 have been obtained from an organic light emitting diode (OLED) using starburst molecule doped with 5,6,11,12-tetraphenylnaphthacene fabricated by wet-processing. We demonstrate that the OLEDs fabricated by wet-processing can be applied to fields of short range optical communication as the electro-optical conversion device for transmitting the signals of moving picture.