Wide-bandgap p-type microcrystalline silicon oxycarbide using additional trimethylboron for silicon heterojunction solar cells



We report a new wide-bandgap p-type microcrystalline silicon oxycarbide (p-μc-SiOxCy:H) film prepared by plasma-enhanced chemical vapor deposition. As an additional doping gas, trimethylboron was introduced into the standard processing gas-mixture of silane, carbon dioxide, hydrogen, and diborane. With both trimethylboron and diborane as doping gases, the optical bandgap (E04) of the formed p-μc-SiOxCy:H film was 0.18 eV higher than that of reference microcrystalline silicon oxide (p-μc-SiOx:H) processed with only diborane doping gas for the same levels of film thickness and electrical conductivity. To demonstrate the effectiveness of the developed p-layer, we applied it as an emitter in silicon heterojunction solar cells, which delivered a markedly high open circuit voltage of 0.702 V and a power conversion efficiency of 18.9% based on a non-textured flat wafer. Copyright © 2017 John Wiley & Sons, Ltd.