Development of high efficiency large area silicon thin film modules using VHF-PECVD

This paper reviews recent work on the development of thin film silicon solar modules and cost-effective production technology. Noting the potential of VHF-PECVD for high rate and high quality deposition,we initiated development of a-Si solar modules. In the first stage,we succeeded in up-scaling a-Si high quality uniform deposition at a high rate of over 1.0 nm/s to a substrate area of 1.1 · 1.4 m2 to achieve high productivity. Next,the large area a-Si solar modules with stable aperture efficiency of 8% were developed,and the commercial production of a-Si solar modules commenced in October 2002. In the second stage,aiming at stable efficiency of 12%,which could make the PV power generating cost below residential electricity prices in combination with cost-effective production technology,we have been developing a- Si/lc-Si tandem solar modules. Recently,tandem modules of 40 · 50 cm2 in size with a lc-Si i-layer prepared at a deposition rate of 2.1 nm/s yielded initial conversion efficiencies of 11.1%. As for small sized lc-Si single cells,technologies with a high deposition rate of 2.5 nm/s and efficiency of 8.8% have already been developed. In addition,by improving the up-scaling and light-trapping techniques,we will achieve our current goal of 12% stable efficiency for a-Si/lc-Si tandem modules at a deposition rate of over 2.0 nm/s,leading to cost-effective mass production. 2004 Elsevier Ltd. All rights reserved.