High-efficiency (21.4%) Ga0.75In0.25As/GaAs (E g=1.15 eV) concentrator solar cells and the influence of lattice mismatch on performance

Abstract

High‐efficiency Ga_0.75In_0.25As/GaAs concentrator solar cells (E_g=1.15 eV, area=0.32 cm²) have been fabricated and tested at 21.4% efficiency under 380 AM2.4 sun. The cell performance parameters of open‐circuit voltage, fill factor, and efficiency are presented as functions of concentration up to 987 sun. The spectral response, and current‐voltage characteristics under concentration, of cells grown by organometallic vapor phase epitaxy on graded and ungraded lattice‐constant buffer layers are compared. It is shown that a graded lattice‐constant buffer layer is necessary for high‐efficiency performance. In general, Ga_0.75In_0.25As cells have higher efficiencies and open circuit voltages than Si cells (E_g=1.11 eV) for concentrations in excess of about 200 sun.