Improved radiation hardness of silicon solar cells

SHARP and NASDA (National Space Development Agency of Japan) have been engaged in the development of silicon space solar cells since 1970s. We started the project to improve the radiation hardness of silicon solar cells in 1998. This project gave fruitful results in BJ (both-side junction) and AHES (advanced high efficiency silicon) structure. The design and manufacturing process for the BJ cells and the AHES-1 cells were finalized and their characteristics were qualified. The experimental results of these solar cells´ performance are compared with conventional HES (high efficiency silicon) cells. The BJ, the AHES-1 and AHES-2 cells showed 13.5%, 13.1% and 13.4% efficiency, respectively, at AM0, 28°C after the irradiation of 1 MeV electrons of 1×10¹⁵ e/m². The EOL efficiency of 13.5% of BJ cell is the highest ever reported for space silicon solar cells. This paper presents the main features of the BJ, the AHES-1 and AHES-2 design and qualification status