High-efficiency heterojunction crystalline Si solar cells

High-efficiency back-contact heterojunction crystalline Si (c-Si) solar cells with record-breaking conversion efficiencies of 26.7% for cells and 24.5% for modules are reported. The importance of thin-film Si solar cell technology for heterojunction c-Si solar cells with amorphous Si passivation layers in improving conversion efficiency and reducing production cost is demonstrated. Our attempts to reduce the production cost of a heterojunction c-Si solar cell by applying a SiO _x layer prepared by a plasma-enhanced CVD method are presented. The characteristics of heterojunction c-Si solar cells are clarified by comparing them with those of practical homojunction solar cells, and crucial targets for industrialization of back-contact heterojunction c-Si solar cells are discussed. Owing to the recent improvement of c-Si solar cells and perovskite solar cells, conversion efficiencies over 30% have become a realistic target by using a two-terminal tandem structure with a heterojunction c-Si solar cell and a perovskite solar cell.