Hole‐Selective Ultrathin Al‐Doped SiOx Passivation Layer Formed by Immersing in Aluminum Nitrate Aqueous Solution

Abstract

Herein, ultrathin Al‐doped SiOx layer formed by immersing in Al(NO3)3 aqueous solution is introduced. This layer enables high‐level surface passivation with a maximum effective surface recombination velocity (Seff,max) < 16 cm s−1 at an excess carrier density (Δn) of 1 × 1015 cm−3 for 2.5 Ω cm n‐type c‐Si without any other processes such as film deposition in a vacuum chamber, high‐temperature annealing, and hydrogenation. This passivation effect presumably comes from negative fixed charges localized in Al‐doped SiOx layers, forming inversion layers due to upward Si band bending at the SiOx/Si interface. In addition, the Al‐doped SiOx layers facilitate accumulated holes at the interface to tunnel through the layers even though the applied bias is extremely low. The high tunnel current density of holes accumulated in the inversion layers implies that these ultrathin Al‐doped SiOx layers are expected to be favorably implemented for high‐efficiency passivating‐contact c‐Si solar cells.