Progress in crystalline multijunction and thin-film photovoltaics

Photovoltaics are important in terrestrial applications such as remote power and renewable energy but are the primary source of electrical power for space systems. For space applications, priorities are high conversion efficiency and resistance to radiation-induced degradation. The emphasis is on III-V multijunction solar cells and comparatively lower efficiency but flexible, lightweight thin-film solar cells. Triple-junction III-V solar cells have reached conversion efficiencies of 30% at air mass zero (AM0). New lattice mismatch techniques and nitride materials hold promise for further efficiency increases. Thin-film solar cells generally have less than 15% efficiency but greater radiation resistance, lower cost, and lower mass.