IZO/ITO Double-Layered Transparent Conductive Oxide for Silicon Heterojunction Solar Cells

Zinc-doped indium oxide (IZO)+tin-doped indium oxide (ITO) is proposed in this study as a double-layered transparent conductive oxide (TCO) for the application of silicon heterojunction (SHJ) solar cells. IZO is consecutively deposited via radio frequency sputtering at room temperature. The electrical and optical characteristics of IZO are examined depending on the thickness and the O₂ flow rate, which ranged from 0 to 5 sccm. The improved photocurrent characteristic for the proposed SHJ solar cell with IZO+ITO is achieved from 40.64 to 41.3 mA/cm² by an OPAL2 solar cell simulation. The sheet resistance of IZO slightly increases from 120 to 130 Ω/□ , which is caused by a decrease in the O₂ vacancy due to an increase in the O₂ flow rate from 1 to 5 sccm. The SHJ solar cells with 4.84 nm IZO deposited at the O₂ flow rate of 4 sccm show the lowest solar weighted reflectance of 4.36%. Therefore, these results indicate that IZO+ITO is expected to increase the efficiency of SHJ solar cells.