POSSポリイミド複合材料を用いた低地球周回軌道用三重接合GaAs薄膜太陽電池の長期封止

Polyhedral oligomeric silsesquioxane (POSS) polyimide is promising for sealing flexible photoelectronic devices for space applications. However, atomic oxygen interaction with POSS polyimide results in a porous SiO_x passivating layer, ultraviolet interaction results in bonding degradation, both causing the transmittance decrease in the visible light range. In this study, the atomic oxygen exposure-induced transmittance decrease of POSS polyimide is explained and simulated by Rayleigh scattering. Ultrathin oxide films and ultraviolet absorbent are introduced to POSS polyimide by surface- and bulk-phase modifications to improve atomic oxygen and ultraviolet resistance, which achieves ≈0 wt% mass loss upon an eight-year long-term atomic oxygen exposure and is deduced by molecular dynamics. The atomic oxygen exposure effect on the sheet resistance of flexible conductive indium tin oxide-POSS polyimide is explained by band structure calculation. The SiO₂-POSS polyimide sealed triple-junction GaAs thin-film solar cell exhibits beginning of life (BOL) and end of life (EOL) efficiencies of 27.67% and 23.38% upon an eight-year long-term to atomic oxygen. The atomic oxygen reactions with polyimide-based films are explained by zero- and first-order reactions, and predictive formulas are created for the film mass loss and sealed solar cell performance under the long-term atomic oxygen exposure. This study suggests a POSS polyimide composite as a packaging film for flexible photoelectronic devices in low Earth orbit.