Electrical and optical properties of Si-doped indium tin oxides as transparent electrode and anti-reflection coating for solar cells

• Silicon-doped indium tin oxide (ITSO) thin films were prepared by co-sputtering of SiO2 and ITO targets.
• Graded refractive index using ITO/ITSO/SiO2 films was fabricated for Si solar cell.
• Anti-reflection (AR) coating layer with graded refractive index was also used for transparent conducting electrodes.
• Simulated AR structure for solar spectral region can raise the current level twice more than that of conventional cell.

We have studied the electrical and optical properties of Si-doped indium tin oxides (ITSOs) as transparent electrodes and anti-reflection coatings for Si-based solar cells. The ITSO thin films were obtained by co-sputtering of ITO and SiO2 targets under target power control. The resistivity of the ITSO thin films deposited at 0.625 in terms of power ratio (ITO/SiO2) were 391 Ωcm. In this condition, the ITSO thin films showed very high resistivity compared to sputted pure ITO thin films (1.08 × 10−3 Ωcm). However, refractive index of ITSO thin films deposited at the same condition at 500 nm is somewhat lowered to 1.97 compared to ITO thin films (2.06). The fabricated graded refractive index AR coatings using ITO, ITSO, and SiO2 thin films kept over 80% of transmittance regardless of their thickness varing from 97 nm to 1196 nm because of their low extinction coefficient. As the AR coating with graded refractive indices using ITO, ITSO, and SiO2 layers was applied to general silicon-based solar cell, the current level increased nearly twice more than that of bare silicon solar cell without AR coating.