High-efficiency heteroepitaxial InP solar cells

High-efficiency, thin-film one-sun and concentrator InP solar cells grown on GaAs substrates are discussed. A novel, compositionally graded heterostructure is used to grow high-quality InP layers. One-sun cells have AM0 efficiencies as high as 13.7% at 25 degrees C (equivalent to 15.7% under the global spectrum). For the concentrator cells at 25 degrees C a peak conversion efficiency of 18.9% under 71.8 AM0 suns has been achieved. Under the direct spectrum, the equivalent efficiency is 21.0% at 88.1 suns. At 80 degrees C, the peak AM0 efficiency is 15.7% at 75.6 suns. Temperature coefficient data for the concentrator cells are also presented. Approaches for further improving the cell performance are discussed.<>