Trends in thin film photovoltaic technology development [for space application]

This paper presents recent developments in thin film photovoltaic technology. Thin film solar cells, though less efficient than single crystal multijunction cells, may hold significant advantages in both cost and weight. For example, a typical thin film cell may weigh about 0.1 kg/m², compared to more than 1 kg/m² for an encapsulated single crystal silicon cell. It is anticipated that as thin film blanket efficiencies increase, these significant weight savings will translate into large cost savings for certain space applications. In particular, small satellites with low power requirements (<5 kW) will benefit most from thin film technology. Cost advantages hold promise for terrestrial applications as well. For terrestrial use, however, the critical metric is cost per watt, while for space other issues, such as radiation resistance, strength and stability under temperature cycling are important. Two promising materials currently being investigated as candidates for higher-efficiency (12-15%) manufacturable blanket photovoltaics are copper indium diselenide on both polymer and thin stainless steel substrates, and amorphous silicon. One or both of these materials may soon reach the cost and efficiency goals necessary for thin film terrestrial cells to compete well in terms of dollars per watt with single crystal technology. Space applications would become feasible even before this threshold, however. Recent progress in the processing and manufacturability of these materials is reviewed, and anticipated developments and trends discussed