Design of metamorphic dual-junction InGaP/GaAs solar cell on Si with efficiency greater than 29% using finite element analysis

Heterogeneous integration of multijunction III-V solar cells on Si is a promising solution for the widespread commercialization of III-V cells. However, the polar on non-polar epitaxy and 4% lattice-mismatch between GaAs and Si results in formation of defects and dislocations, which can significantly impede the minority carrier lifetime and hence the cell performance. We have investigated the impact of threading dislocation density on the performance of dual-junction (2J) n+/p InGaP/GaAs solar cells on Si. Using our calibrated model, the metamorphic 2J cell on Si was optimized by tailoring the 2J cell design on Si to achieve current-matching between the subcells at a realistic threading dislocation density of 10⁶ cm^-2. We present a novel 2J InGaP/GaAs cell design on Si at a threading dislocation density of 10⁶ cm^-2 which exhibited a theoretical conversion efficiency of greater than 29% at AM1.5G spectrum, indicating a path for viable III-V multijunction cell technology on Si.