Recent developments in high-efficiency Ga0.5In0.5P/GaAs/Ge dual- and triple-junction solar cells: steps to next-generation PV cells

Dual-junction Ga0.5In0.5P/GaAs solar cells on Ge substrates have rapidly go ne from small, high-efficiency laboratory cells, to large-area, high-effici ency cells manufactured at spectrolab in high volume. Over 500,000 of these dual-junction (DJ) cells with 27-cm(2) area have been produced, with avera ge AMO load point efficiency of 21.4%. The next step in the evolution of th is type of multijunction solar cell has been taken, with the development of triple-junction (TJ) Ga0.5In0.5P/GaAs/Ge cells. The addition of the german ium third junction, plus several significant improvements in the device str ucture, have led to a measured efficiency of 27.0% (AMO, 28 degreesC) at Sp ectrolab on large-area (> 30 cm(2)) TJ cells. The TJ cell is now in product ion at Spectrolab. Ga0.5In0.5P/GaAs/Ge cells are viable not only for non-co ncentrating space applications, but also for terrestrial and space concentr ator systems. Efficiencies up to 32.3% at 47 suns under the terrestrial AM1 .5D spectrum have been achieved. (C) 2001 Published by Elsevier Science B.V . All rights reserved.