Highly Transparent and High Haze ZnO:Al film For Front TCO of a-Si:H and μc-Si:H Solar Cells by Controlling Oxygen Flow

We fabricated highly transparent and high haze ZnO:Al film for front TCO of amorphous and microcrystalline silicon solar cells. We have sputtered ZnO: Al film of 1.3 mu m on the thin seed layer of about 80nm which was previously sputtered on the glass substrate by using 4% dilution of oxygen to argon gas. The ZnO: Al film grown on the seed layer had much higher crystalline phase than one without any seed layer. Our bi-layer ZnO: Al film showed low resistivity of 2.66x10(-4) Omega.cm and sheet resistance of 2.08 Omega/square while conventional ZnO: Al film showed resistivity of 3.24x10(-4) Omega.cm and sheet resistance of 2.46 Omega/square. After surface texturing by 0.5% HCl wet-chemical etching, the transmittance of ZnO: Al film was increased from 83.7% to 88.1% at wavelength of 550nm through the seed layer. Also the transmittance at 800nm was increased from 82.3% to 88.9%. Especially, haze values of the ZnO: Al film were drastically increased from 58.7% to 90.6% at wavelength of 550nm by employing the seed layer. Also haze values at 800nm were increased from 22.1% to 68.1%. It is expected that the seed layer method to improve the quality of ZnO: Al film will contribute to an increase of solar cell efficiency due to the high capability of light trapping and low electrical resistivity.