Editors' Choice—Silicon Electrodeposition in a Water-Soluble KF–KCl Molten Salt: Utilization of SiCl4 as Si Source

Abstract

The electrodeposition of Si was investigated in a molten KF–KCl salt mixture (eutectic composition, 45:55 mol%) after the introduction of SiCl4 to demonstrate a new production method for solar cell substrates. Gaseous SiCl4 was introduced directly into the molten salt at 1023 K by a vapor transport method using Ar as a carrier gas. The dissolution efficiency of SiCl4 exceeded 80% even when a simple tube was used for bubbling. Galvanostatic electrolysis was conducted at 923 K on a Ag substrate at 155 mA cm−2 for 20 min in the molten KF–KCl salt mixture after the dissolution of 2.30 mol% SiCl4. Although a compact Si layer was formed, its smoothness was inferior to that obtained from the melt after the addition of K2SiF6. The molar fraction of the fluoride anion is suggested as one of the factors affecting the morphology of the deposits.