Selective Dry Etching of p-Type Si Films for Photolithography Processing of Interdigitated Back Contact Silicon Heterojunction Solar Cells

Abstract

Highly doped p-type Si thin films are hardly etched by alkaline etchants unlike i- and n-type Si films. In addition, the use of a HNO3/HF/H2O mixture to etch p-type Si films can lead to inhomogeneous etching of p-type Si films and consequently result in excessive surface roughness and inferior surface passivation. For these reasons, we have implemented a dry etching method to selectively pattern p-type Si films for interdigitated back contact (IBC) silicon heterojunction (SHJ) solar cells using a SiO x masking layer. In this way, the underlying passivation layer and the Si surfaces can be undamaged. In this study, the etch rates of all Si films that make up IBC-SHJ solar cells have been investigated in order to obtain high etch selectivity and establish proper patterning steps. Furthermore, we have fabricated IBC-SHJ solar cells on planar wafers by using dry and wet patterning methods developed in this study. As a result, a conversion efficiency of 15.7% is obtained with V oc of 682 mV, J sc of 33.8 mA/cm2, and FF of 0.68.