Satoru Toguchi

Novel red organic electroluminescent materials including perylene moiety

Abstract We have reported organic electroluminescent (EL) materials with functionally separated molecular structure, which are composed of a luminescent center such as a fused aromatic ring and charge transfer units such as styryl-substituted diphenyl amino groups. This structure is a key to the design of light-emitting materials with controllable EL characteristics. Thus, we have already reported that a naphthalene moiety designed as a luminescent center with styryl-substituted diphenylamino groups as charge transfer unit gives blue light emission with high efficiency [A. Oda, E. Hasegawa, Mol. Electron. Bioelectron. 10 (1999) 12 (in Japanese)]. In this report, we describe the application of a perylene moiety to this structure to obtain red-light-emitting materials. Triple-layered EL devices using five perylene compounds with or without a styryl substituent on diphenylamino groups have a maximum brightness of 4800 to 8700 cd/m 2 . In the case of styryl-substituted compounds, the devices have orange to reddish-orange emission with peaks at about 580 nm and shoulders at about 620 nm. Due to the shoulders at longer wavelength side of peaks, the CIE coordinate of the emission of a device shifts to (0.64, 0.35), which is almost the same as that of the red color of CRT. Thus, our molecular design method is proved to be useful for controlling color emission from blue to red. On the other hand, devices using compounds without a styryl substituent have yellowish-green to yellow emission and peaks at about 560 nm. We examined the effects of the substitution on the end of the charge transfer unit. The current density vs. applied voltage characteristics of the devices are affected by methyl substitution on styryl groups. The efficiencies are almost independent of the current density in the devices with styryl-substituted compounds, but rapidly decrease in the case of compounds without a styryl substituent.

High Performance Vertical-Type Organic Transistors And Organic Light Emitting Transistors

We have fabricated organic static induction transistor (SIT) and organic light emitting transistor (OLET) combining SIT with organic light emitting diode (OLED). SIT and OLET have a grid-type Al gate electrode that was formed using a shadow evaporation mask in the organic semiconductor layers. The effective electrode area of SIT and OLET is approximately 4 mm2. By optimizing the device structure, excellent performances of SIT and OLET were obtained. The drain-source current (IDS) at a constant drain-source voltage (VDS) decreases with increasing the gate voltage (VG). The current is controlled by relatively small VG (-10 V) and a typical SIT characteristic is obtained in the OLET. The luminance of OLET also varies corresponding to the I-V characteristics. The maximum current and luminance values were approximately 10 mA and 10,000 cd/m2, respectively. We have also investigated the electrical characteristics of organic SITs having several gate gaps. The organic SIT with gate gap (Dg) less than 200 nm have much smaller off currents and much larger on/off ratios.