As potential lighting-emitting devices, electrochemiluminescence (ECL) devices are promising in terms of device structure and fabrication and involve low processing cost compared to organic light-emitting devices (OLEDs).

An organic, electrically bistable device with a novel charge trap system (CTS, LiF/Al/LiF) in the crossbar structure of Al/Alq3/(LiF/Al/LiF)/Alq3/Al was fabricated to develop a vertically oriented crossbar array memory device. The novel concept of CTS with thickness control (2, 4, and 6nm) of an insulating LiF layer was introduced. The CTS with a 4.0nm-thick LiF layer displayed non-volatile memory behavior with a hysteresis having large ON/OFF ratio (more than three orders of magnitude) and had the ability of writing–reading–erasing–reading cycles. No significant degradation of the device was observed in either the ON or OFF state after continuous stress testing (>2000s).

Highly efficient blue and white phosphorescent organic light-emitting diodes (PHOLEDs) with an exciton-confining structure were investigated in this study. Effective charge confinement was achieved by stacking two emitting layers with different charge-transporting properties, and blue PHOLEDs with a maximum luminance efficiency of 47.9 lm/W were developed by using iridium(III) bis(4,6-(difluorophenyl) pyridinato-N,C2')picolinate (FIrpic) as an electrophosphorescent dopant. Moreover, when the optimized green and red emitting layers were sandwiched between the two stacked blue emitting layers, white PHOLEDs (WOLEDs) with peak external and luminance efficiencies of 19.0

The performances of deep blue phosphorescent organic light-emitting diodes (PHOLEDs) have been investigated by changing the combination and the composition of host materials in a mixed host emissive layer (EML). An electron transport-type host material of m-bis-(triphenylsilyl)benzene (UGH3), was combined with an hole transport-type host materials, N,N′-dicarbazolyl-3,5-benzene (mCP) or 4,4′,4′′-tris(N-carbazolyl)triphenylamine (TcTa) both doped with a deep blue electro-phosphorescent dopant of iridium(III)bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). We found that a mixed host structure was effective to control the charge carrier injection and transport in EML. Therefore, we obtained highly improved efficiency in deep blue PHOLEDs with peak external quantum and luminance efficiencies of 22.9% and 39.2lm/W with maintaining Commission Internationale de L’Eclairage (CIE) coordinates of (x=0.163, y=0.287).

We fabricated blue fluorescent organic light-emitting diodes (OLEDs) by using a laser patterned ITO anode. An indium tin oxide (ITO) layer was defined directly with an infrared laser system (wavelength = 1064 nm), which was carried out at an optimum laser focal position, 1 W of laser power and 500 m/s of laser scanning speed. As a result, the problems with the laser patterning method, such as a shoulder at the ITO/glass edge, crack on the surface, and ITO debris were minimized. Moreover, we found that the OLED with laser patterned ITO showed almost similar electrical and optical properties to that of ITO that was patterned by photo-lithography.

We have fabricated transparent white organic light emitting diode (WOLED) for lighting application based on a hybrid white OLED and a phosphorescence white OLED. For the hybrid WOLED, a blue fluorescence emitting layer (FLEML) and green and red phosphorescence emitting layers (PH-EMLs) have been used in the device structure of ITO/hole transporting layer (HTL)/PH-EMLs/interlayer/FL-EML/ETL/LiF/Al. The balanced emissions from the FLEML and the PH-EMLs have been obtained by using appropriate carrier (hole) trapping effects in the PH-EMLs, which resulted in external and power efficiencies of 15 % and 27 lm/W, respectively, at a luminance of 1000 cd/m2 without any out-coupling enhancement. The Commission Internationale de L'Eclairage (CIE) coordinates of this hybrid WOLED is (0.43,0.44) with color rendering index (CRI) of 80 and correlated color temperature (CCT) of 3200 K, respectively, in the bottom emission structure. Based on this hybrid WOLED, we established highly efficient transparent WOLED by introduction of a transparent cathode, and obtained over 19 lm/W of power efficiency at a total luminance of 1000 cd/m2 as well as over 60 % of transmittance at 550 nm with the conventional glass encapsulation. Moreover, when the phosphorescent white OLED was combined with a transparent cathode, the power efficiency was reached up to 24 lm/W of power efficiency at a total luminance of 1000 cd/m2.

We have studied transparent bottom-gate TFTs (thin film transistors) using amorphous IGZO (In-Ga-Zn-O) as an active channel material. The TFT devices had inverse co-planar structures. Source/drain and gate electrodes were constituted by ITO sputtered with a DC-RF magnetron sputter system, and an alkaline-free glass was used as a substrate. The gate insulator was Al(2)O(3) formed by using an atomic layer deposition (ALD) method at 150 degrees C. An active layer was formed by off-axis RF magnetron sputtering and post-annealing was performed with a hot plate or a vacuum oven. The field effect mobilities and the sub-threshold swings of the IGZO TFTS were 12 similar to 18 cm(2)/Vs and 0.2 similar to 0.6 V/dec, respectively. However, the hysteresis on I-V characteristics was relatively large without passivation. Thus. we passivated the TFT devices with inorganic and organic materials. After the organic passivation and post-heat treatments, the hysteresis was remarkably reduced Without deterioration of the electrical characteristics.