Structural optimization and growth of intrinsic hydrogenated amorphous silicon films by HWCVD

Abstract

Although the silicon heterojunction (SHJ) solar cell is the crystalline silicon solar cell with highest conversion efficiency at present, its higher cost of production line has been a factor restricting its industrial development. The use of hot wire chemical vapor deposition (HWCVD) technology instead of the mainstream plasma enhanced chemical vapor deposition (PECVD) technology for the deposition of amorphous silicon films can effectively reduce the cost of equipment and processing, and has a bright future. In recent years, i-a-Si:H films grown by PECVD have obtained great improvement in passivation quality, whereas HWCVD technology has been neglected in this field. This has significantly limited the development and application of HWCVD technology in SHJ cell production. In this work, we exploited the differences in the films properties and microstructures deposited by various hot-wire temperatures and successfully developed a structure for the high-passivation-quality i-a-Si:H film grown by HWCVD, consisting of a buffer layer and a double-layer bulk stack. By introducing the buffer layer grown with the 1650 °C hot-wire temperature and pure silane, the effective minority carrier lifetime was improved from 2.3 ms to 7.5 ms, and a cell efficiency enhancement of 0.4%abs was obtained. By depositing the bulk layer sequentially with hot-wire temperatures of 1800 °C and 1900 °C, the passivation quality and the conductance were both improved. An effective minority carrier lifetime of 8 ms and a further cell efficiency enhancement of 0.15%abs were obtained. Finally, SHJ solar cell efficiency of 24.35% was obtained with a home-made HWCVD-based pilot SHJ cell line.