Overview for Tandem Solar Cell R&D Activities in Japan

The development of high-performance solar cells offers a promising pathway toward achieving high power per unit cost for many applications. Because state-of-the-art efficiencies of single- junction solar cells are approaching the Shockley-Queisser limit, the multi-junction (MJ) solar cells are very attractive for high-efficiency solar cells. Although the concept of MJ solar cells was first and most successfully implemented using III-V compound materials, there is a need to further improve their conversion efficiency and rduce cost. The Si tandem solar cells have great potential of cost reduction by maining high-efficiency with an efficiency of more than 37% with 2-junction and 43% with 3-junction. This paper reviews Japanese R&D activities for III-V compound MJ solar cells. As the most recent R&D activities, developments of high-efficiency and low cost III-V/Si tandem solar cells and modules are presented in this paper.