Experimental study of solar cell performance versus dislocation density

The results of an experimental study of solar cell performance and material properties as a function of dislocation density are reported. Buffer layers of GaAs_y-1P_y (y=0-0.32) have been used to controllably introduce dislocations into GaAs-on-GaAs cells. Bulk space-charge recombination is found to be the dominant mechanism operating at high defect densities. The experimental results indicate that a dislocation density ⩽5×10⁵ cm^-2 is needed for the production of high-efficiency GaAs-on-Si solar cells. Results to date have yielded concentrator cells with Am 1.5 efficiencies of up to 20% at 210 suns in GaAs-on-Si layers containing 1×10⁷ dislocations/cm^-2, as compared with GaAs homoepitaxial cells that are 29% efficient under concentrated sunlight