The Design of Single-Junction GaAs and Dual-Junction GaAs/Si in the Presence of Threading Dislocation Density

We have studied the impact of threading dislocation density (TDD) on the performance of GaAs associated with the epitaxial growth on silicon (Si) substrate in either single-junction GaAs or dual-junction two-terminal GaAs/Si solar cell devices. The performance is measured under truncated spectrum due to the presence of internally lattice matched top GaInP filter with GaAs sub-cell. It is found that cell thickness is an important design parameter, with thinner active GaAs junctions required for single-junction design with higher TDD. Conversely, a thicker active GaAs junction is needed for dual-junction structure to ensure current matching with the bottom Si sub-cell. In addition, the homo-junction buffer layer or back surface field (BSF) improves the conversion efficiency for both structures, and most significantly for materials with higher TDD.