Application of advanced plasma treatment in the a-Si:H(i)/μc-SiOxH(n) interface of silicon heterojunction solar cells

Hydrogen (H 2 ) plasma treatment (HPT) and carbon dioxide (CO 2 ) plasma treatment (CO 2 PT) are often used to enhance the crystallinity of the microcrystalline silicon (μc-Si:H (p)) or microcrystalline silicon oxide (μc-SiOx:H (p)) emitter in silicon heterojunction (HJT) solar cells. In this paper, the CO 2 PT is first applied to treat the intrinsic amorphous silicon (a-Si:H(i)) layer before the deposition of the n-type μc-SiOx:H(n) window layer of HJT solar cells. It is found that the CO 2 PT effectively improves the crystallinity but degrades the interface passivation quality. Consequently, it does not improve, but degrades the HJT cell performance. To resolve this issue, we develop an advanced plasma treatment with H 2 and CO 2 mixture and find that the optimized (H 2 +CO 2 )PT not only improves the crystallinity, thereby increasing the conductivity as well as the light transmittance of the μc-SiOx:H(n) to improve short circuit density (J sc ), but also improves interface passivation to reduce recombination loss, thereby improving fill factor (FF). As a result, the FF is improved by 0.11% absolutely, and J sc by 0.27 mA/cm 2 . The average conversion efficiency of the HJT solar cells fabricated with a mass-production PECVD system reaches 25.73%. • CO₂PT was used at a‑Si:H(i)/μc‑SiOx:H(n) interface in HJT cells to improve the window layer crystallinity. • CO₂/H₂ plasma treatment mitigates passivation degradation from conventional CO₂ plasma treatment. • Compared with HPT-only samples, (CO₂+H₂) PT-treated samples showed an absolute efficiency improvement of 0.21%.