Suppression of the epitaxial growth of Si films in Si heterojunction solar cells by the formation of ultra-thin oxide layers

• We apply surface oxidation to Si(111) for the suppression of epitaxial growth.
• Epitaxial growth can be prevented by formation of the thin oxide layers.
• a-Si/c-Si structures with oxidation have better carrier lifetimes.
• The oxidation is effective to improve the performance of SHJ solar cells.

The epitaxial growth of silicon (Si) films during the catalytic chemical vapor deposition (Cat-CVD) of intrinsic amorphous Si (i-a-Si) passivation films on crystalline Si (c-Si) wafers is suppressed by the oxidation of c-Si surfaces simply by dipping the c-Si wafers in hydrogen peroxide (H2O2). This oxidation treatment is also effective for (111)-oriented c-Si surfaces particularly at high a-Si deposition temperatures. The suppression of the epitaxial growth leads to the better effective minority carrier lifetime (τeff) of c-Si wafers passivated with Cat-CVD i-a-Si films. SHJ solar cells show remarkably high open-circuit voltage (Voc) exceeding 0.7 V. These results clearly show the effectiveness of the insertion of SiOx layers on the improvement in Cat-CVD a-Si/c-Si interfaces.