Overview of High-efficiency Multi-junction Solar Cells and Discussion about Roles of Surface, Interface and Defects

Abstract

Development of high-efficiency solar cells is very important for clean energy society based on photovoltaics. Multi-junction solar cells are very attractive as high-efficiency solar cells because 2-junction and 3-junction solar cells have high-efficiency potential of more than 36% and 42%, respectively. This paper overviews present status of multi-junction solar cells. As a results of reducing non-radiative recombination and resistance losses, 39.5% efficiency has been demonstrated with 3-junction solar cell. In addition, understanding and controlling defects, surface recombination and interface recombination are shown to be very important in order to improve efficiency of multi-junction solar cells. Brief overview for Si tandem solar cells composing of III-V, II-VI, chalcopyrite, perovskite top cells and Si bottom cell is also presented.