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. We propose a novel p‐type wide‐bandgap silicon oxycarbide materials and its film preparation. The new p‐type microcrystalline silicon oxycarbide (p‐μc‐SiOxCy:H) films with additional trimethylboron doping exhibited average wide bandgaps (E04) about 2.18 eV. This new film was employed as an emitter of HIT‐type c‐Si solar cells and found that it boosts mainly Voc because of wide E04 and thus power conversion efficiency of 18.9 % based on non‐textured flat wafer was attained.