First space flight of advanced III-V solar cells

The first year of operation of the Varian experimental space panel is discussed. Both single-junction GaAs cells and components of monolithic multijunction cells are part of the experiment. Both types of cell are briefly described. The multijunction component cells include 1.93 eV AlGaAs, which serves as the upper cell in a GaAs/AlGaAs two-junction cascade or an InGaAs/GaAs/AlGaAs three-junction structure, and 1.75 eV AlGaAs, which serves as the upper cell in an InGaAs/AlGaAs two junction cascade. Each of the cells is individually monitored, allowing direct evaluation of structures that have not previously been exposed to the space environment. Typical current-voltage characteristics of the three major types of cell are summarized. All AlGaAs cells performed better on the space panel than anticipated, and no measurable degradation has been observed over a period of over a year in orbit.