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

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 SiOx 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/cm(2), and FF of 0.68.