Progress in High Conversion Efficiency a-Si/μc-Si Tandem Solar Cells and Modules

Abstract

ABSTRACTA fabrication technology for high-quality, device-grade microcrystalline silicon (μc-Si) thin film with a higher deposition rate has been required to reduce the production cost of amorphous silicon (a-Si)/μc-Si tandem modules. Localized Plasma Confinement CVD (LPC-CVD) has been proposed as one solution to this problem. It was found that this CVD is suitable for the deposition of high crystalline fractions and (220) orientation in the development of small-to-medium-size substrates. Since then, we have been developing high-rate deposition technology for production-size substrates by using the essence of LPC-CVD and evaluation techniques for μc-Si materials and plasma. A stabilized module efficiency of 11.1% was reported with a very high deposition rate on a production-size substrate. To improve conversion efficiency, we have been focusing on elemental technologies as well as high-rate deposition technology. Stabilized conversion efficiency of 12.2% for small-size cells (1 cm2) and stabilized module conversion efficiency of 10.7% for production-size substrates were achieved.