Production of indium phosphide solar cells for space power generation

A large-scale commercial process for producing high-efficiency n⁺-p homojunction InP solar cells is described. The n⁺-p junction is fabricated by diffusing sulfur into p-type InP substrates in a sealed quartz ampoule. In one diffusion cycle, 300 1*2 cm² cells are fabricated from 50 2-in. InP wafers. The dependence of solar cell parameters on diffusion temperature and substrate carrier concentration and further improvement of cell performance by mesa etching are also discussed. The conversion efficiency of the best 2*2 cm² cell is 16.6% (total area, one-sun, air mass zero).