Development of thin film silicon solar cells using PCVD process

The authors are developing low cost, thin film silicon solar cells utilizing plasma chemical vapor deposition (PCVD) process, which is suitable for the large scale production. The development consists of mainly three themes; the preparation of low cost lattice matched substrate, the deposition of silicon thin layer using PCVD process, and solar cell fabrication technology. In this paper, the authors emphasize the PCVD thin film silicon deposition process. Epitaxial silicon films of 15-μm thickness were grown on the n⁺ silicon (100) substrate by the PCVD method using SiH₄/SiF₄/H₂ mixture gases at a very low temperature of 200°C. A conversion efficiency of as high as 11.4% has been achieved in the solar cell with this epitaxially grown layer as an active layer. To fabricate solar cells on these low-temperature grown epitaxial silicon layers, the authors developed a novel, low-temperature solar cell fabrication process using PCVD. This simple cell fabrication method yielded a solar cell efficiency of 18.0% on n^- silicon (100) substrate. These technologies were applied to the fabrication of solar cells on the low-cost, plasma-sprayed polycrystalline silicon substrate and the cell efficiency has reached up to 8.4%