Beom-Rak Choi

Surface treatment of indium tin oxide by SF6 plasma for organic light-emitting diodes

SF6 plasma treatment of indium tin oxide highly improves the power efficiency and the stability of the organic light-emitting diode based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4phenylenevinylene]. The treatment leads to a slight reduction in the surface roughness and a decrease in the surface content of Sn. The major effect, however, has to do with the surface incorporation of fluorine. This fluorinated surface improves the hole injection and thus the device performance.

Tailoring of self-assembled monolayer for polymer light-emitting diodes

The choice of a self-assembled monolayer (SAM) is tailored to specifically remove water on an indium-tin oxide electrode and to reduce barrier height for long-term stability of polymer light-emitting diodes. Water, which is a major cause of long-term degradation, is shown to have entirely reversible effects on the power efficiency of the device. It is shown that the use of a SAM for the specific purposes results in a more than an order of magnitude increase in the half lifetime of the device based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene].

Control of silicidation in HfO2∕Si(100) interfaces

The interfacial states of the HfO2 thin film grown on the Si(100) substrate by the pulsed laser deposition method is investigated in situ using x-ray photoelectron spectroscopy. They are found to depend on the HfO2 film thickness, oxygen pressure during the pulsed laser deposition growth, and the deposition process. The hafnium silicide is formed in an oxygen-deficient condition, and it can be most effectively controlled by the ambient oxygen pressure during film growth. The close relation between the silicide formation and abundance of the silicon suboxides at the interface is presented.

Polyaniline and poly(N-vinylcarbazole) blends as anode for blue light-emitting diodes

Polyaniline and poly(N-vinylcarbazole) (PANI:PVK) blends are introduced as an anode, and the advantages are demonstrated for organic light-emitting diodes (LEDs). Compared to the usual PANI network electrodes, use of the blend allows for simpler fabrication and provides a better planarized surface, especially for the device with vapor-deposited emitting layer. PANI is not usually used for blue LEDs because of its strong light absorption in the deep-blue spectral region. This problem is practically solved by the use of the blend.