Porous antimony-doped tin oxide (ATO) cathodes formed by supercritical CO2 (SCCO2) treatment for silver electro-deposition devices were proposed. The porous ATO cathode with a thickness of 1.4£gm was formed by coating the nano-particle ATO solution on ITO glass. The porous structure of the cathodes was obtained by applying SCCO2 treatment at 60oC on the spin-coated ATO thin films. A layer of electrolyte(formed by AgI, NaI and DMSO)was enclosed by two electrodes to to form a so-called¡§sandwich¡¨ structure. After the fabrication process, white paint was spray on the back side of the glass substrate. Due to the thickness of the ATO cathode, the cathode is observed to be transparent during the oxidation process. The Black state of the device was observed during the reduction of silver molecules which were anchored onto the surface of the 1.4£gm thick ATO cathode. The average transmission contrast ratio of 4.4 was obtained in visible spectrum at a driving voltage of 1V and a saturation current density of 3.1 mA/cm2. In addition to that, 0.5 cm by 0.5 cm device with 65£gm cell gap and 0.08 M electrolyte concentration, an electrochromic switching time of 3.7 seconds was achieved .

Porous metal oxides formed by supercritical carbon dioxide (SCCO2) treatments at low temperature were used for displays, solar cells, and light emitting diodes (LEDs) applications. The SCCO2 fluid, also known as green solvents, exhibits low viscosity, low surface tension and high diffusivity as gases, and high density and solubility same with liquids. In this thesis, we successfully fabricated porous antimony-doped tin oxide (ATO) and porous indium tin oxide (ITO) by the SCCO2 treatments. In addition, the treatment can also be used to improve the work function and surface energy of ITO anode of an organic LED (OLED). The performance of the OLEDs was drastically enhanced in comparison with that of the devices without any ITO surface treatments. First, the porous ATO films were formed by the SCCO2 treatment for absorption of silver molecules in silver electro deposition devices. The porosity, resistivity and average optical transmittance of the porous ATO film in visible wavelength were 43.1%, 3 £[-cm and 90.4%, respectively. For the silver electro deposition devices with the porous ATO film, the transmittance contrast ratio of larger than 12 in visible spectrum was obtained at an operating voltage of 1.5 V. Furthermore, for the 0.25 cm2 device, the switching time of 4.5 seconds was achieved by applying a square-wave voltage ranging from 1.5 to -0.2 V between the electrodes. On the other hand, the porous ITO with low refractive index was prepared by SCCO2/IPA treatment on gel-coated ITO thin films. The high refractive index of the ITO film was achieved by long-throw radio-frequency magnetron sputtering technique at room temperature. The index contrast (£Gn) was higher than 0.6 between porous ITO and sputtered ITO films. The large £Gn is useful for fabricating conductive anti-reflection (AR) and high reflection (HR) structures using the porous ITO on sputtered ITO bilayers. The weighted average reflectance and transmittance of 4.3% and 83.1% were achieved for the double-layer ITO AR electrode with a sheet resistance of 1.1 K£[/¡E. For HR structures, the reflectance and sheet resistance were 87.9% and 35 £[/¡E with 4 periods ITO bilayers. Finally, the SCCO2 treatments with strong oxidizer H2O2 were proposed to modify surface property of ITO anode of a fluorescent OLED. The highest work function and surface energy of 5.5 eV and 74.8 mJ/m2 was achieved by the SCCO2/H2O2 treatment. For the OLED with 15 min SCCO2 treatment at 4000 psi, the turn-on voltage and maximum power efficiency of 6.5 V and 1.94 lm/W were obtained. The power efficiency was 19.3% and 33.8% higher than those of the OLEDs with oxygen plasma treated and as-cleaned ITO anodes.