발광층 두께에 따른 유기발광소자의 임피던스 특성 = Impedance Characteristics of Organic Light-Emitting Diodes depending on the Emissive Layer Thickness

다국어 초록 (Multilingual Abstract)

Layer-thickness dependent impedance of organic light-emitting diodes was investigated. Impedance was varied depending on the layer thickness due to a variation of resistance and capacitance. And corresponding Cole-Cole semicircle and 1/τ were investigated. Emissive organic layer was thermally evaporated to a thickness of 100, 200, and 300nm in a structure of ITO/Alq_(3)/Al. As the Alq_(3) layer thickness increases in organic light-emitting diodes, a magnitude of impedance increases. A magnitude of phase shows a capacitive behavior at 0V for 100nm, and negative-resistance behavior in the range of 6～10V, and resistive behavior upto 22V. For devices with 200 and 300nm organic layer thickness, they show a capacitive upto 12V, and resistive behavior near 22V where the phase becomes 0°. A Cole-Cole plot shows that the radius increases as the organic-layer thickness increases. From this analysis, an equivalent circuit could be deduced. The capacitance of the bulk decreases as the layer thickness increases, which is expected.