High-efficiency thin-film AlGaAs-GaAs double heterostructure solar cells

AlGaAs-GaAs double-heterostructure solar cells were fabricated in 10 mu m-thick films and exhibited one-sun, total-area conversion efficiencies up to 19.5% AM0, and 22.4% AM1.5. The cell structure consisted on an n-doped GaAs emitter and p-doped GaAs base interposed between AlGaAs layers. The cell structure was deposited by organometallic vapor-phase epitaxy on a GaAs CLEFT substrate, and later mechanically separated from the substrate during cell fabrication. A single-layer antireflection coating was used without a coverglass. The cells, fabricated on 2 in diameter wafers, had areas of either 1 or 4 cm². Reuse of the substrate was successfully demonstrated. For comparison, cells fabricated with a conventional process from double heterostructures deposited on bulk GaAs substrates exhibited one-sun AM1.5 efficiencies as high as 23.7%. The impact of these high efficiencies on space and terrestrial applications is discussed.