HWCVD growth of hydrogenated nanocrystalline silicon oxide window layers for SHJ solar cells

In recent years, successful development of n-type hydrogenated nanocrystalline silicon oxide (n-nc-SiOx:H) window layers with high conductivity and low parasitic absorption, grown by plasma enhanced chemical vapor deposition (PECVD) technology, has significantly enhanced the power conversion efficiency of silicon heterojunction (SHJ) solar cells. Although SHJ solar cells have significant advantages in efficiency, the high cost of the PECVD equipment presents a significant barrier to their mass production. The utilization of the more cost-effective hot wire chemical vapor deposition (HWCVD) technology presents a promising solution. Nevertheless, HWCVD technology currently lacks an industrially viable methodology for growing high-performance window layers due to a phenomenon of associated severe loss of passivation. In this work, the phenomenon and the solution have been investigated. The results demonstrate that, in HWCVD processes, large amounts of hydrogen and small amounts of oxygen, which are essential for enhancing the crystallinity and conductivity and reducing the parasitic absorption, both induce significant damage to the previously grown intrinsic hydrogenated amorphous silicon layer, leading to poor passivation, and hence much lower cell efficiency. Introduction of a densified amorphous silicon barrier layer was found to be an effective solution to the aforementioned passivation loss, resulting in the successful growth of nc-SiOx:H window layers by HWCVD, with an efficiency enhancement of 0.37%abs. Finally, a commercial-size SHJ solar cell with an efficiency of 24.74 % was fabricated using a home-made HWCVD-based pilot SHJ cell line. •Both hydrogen and oxygen can cause significant damage to the i-a-Si:H layer when depositing n-nc-SiOx:H film by HWCVD.•A barrier layer was developed to protect the i-a-Si:H layer, yielding an efficiency enhancement of 0.37%abs.•A HWCVD-based SHJ solar cell with an efficiency of 24.74 % at a commercial size can be achieved.•A practical and novel window layer for large-scale production of SHJ solar cell by HWCVD has been designed.