The purpose of the thesis is to investigate the improvement of single-crystal Si solar cell efficiency using porous Indium tin oxide (ITO)/ITO double layer antireflection(AR) coating. The resistivity, transmittance and refraction index of the porous ITO films prepared by supercritical CO2 treatment were investigated. At a 2000 psi pressure and 60¡CC, the resistivity of porous ITO films is 15 £[-cm, the average transmittance is better than 95 %, and the refraction index is 1.54. In addition, the resistivity of ITO thin films fabricated by reactive ratio-frequency magnetron sputtering is 7¡Ñ10-4 £[-cm, the average transmittance are 85 %, and the refraction index is 2.0. For the single crystal-Si solar cell with porous ITO/ITO double layer AR coating, the open circuit voltage, short circuit current, fill factor and efficiency are measured.