Combinatorial exploration of new transparent conducting oxide films by using radio frequency sputtering and their applic
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Combinatorial exploration of new transparent conducting oxide films by using radio frequency sputtering and their application in optoelectronic devices Tae-Won Kim1, Gi-Soek Heo2, Ho-Sung Kim1 and Jong-Ho Lee2 1 Energy and applied optics research group, Korea Institute of Industrial Technology, 1110-9, Oryong-dong, Buk-ku, Gwangju, 500-420, Republic of Korea. 2 NCNE, Korea Institute of Industrial Technology, 1110-9, Oryong-dong, Buk-ku, Gwangju, 500420, Republic of Korea. ABSTRACT The purpose of this study is to develop new transparent conducting oxide (TCO) films by using combinatorial approach and to apply them for organic light emitting diodes (OLED) and/or thin film photovoltaic devices. For this, we have explored several TCO films with multicomponents and optimized their properties by employing combinatorial sputtering system. For the first, we have fabricated combinatorial libraries composed Zn-In-Sn-O (ZITO) to reduce In content comparing with Sn-doped indium oxide (ITO). The ZITO films showed amorphous structure at the substrate temperature ranged RT~ 350 °C, high transmittance over 85% at the visible range wavelength, and resistivity as low as 3x10-4~10-3Ωcm. These results reveal that the ZITO films have indium composition as low as 30~40% comparing with equivalent ITO films. Furthermore, we have fabricated OLED on glass substrates by using the amorphous ZITO anode. OLED fabricated on amorphous ZITO-coated glasses have exhibited good characteristics comparable to OLED on ITO films. Besides OLED, the amorphous ZITO TCO can be applied for other optoelectronic devices like electronic paper, thin film photovoltaic, and smart window. INTRODUCTION TCO films have been widely used for optoelectronic devices: transparent electrodes in flat panel displays and solar cells; transparent heating elements for automobile and aircraft windows; transparent heat-reflecting window material for buildings, lamps, and solar collectors; gas sensors; and antireflection coatings due to their low resistivity and high transmittance characteristics [1-4]. It is known that In2O3:Sn (ITO) thin films have been practically used as transparent electrodes for most of the various types of flat panel displays. For the ITO films, doping of In2O3 films with Sn increases their electrical conductivity, since the Sn4+ substitutes for the In3+ cation, creating a donor level in the energy band gap. Though it shows excellent optoelectronic properties, its expensive cost, instability at high temperatures, and low stability against external bending are drawbacks to the application of various optoelectronic devices. Above all, the total amount of In used for various optoelectronic applications has been expanding remarkably recently. It is widely believed that a shortage of In may occur in the near future because of the limited nature of the world's In reserves. Therefore, it is important to develop alternatives to the ITO film as a TCO application. Recently, TCOs that contain a reduced amount of In or none at all have attracted much attention as substitu
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