Designing an Epitaxially-Integrated DBR for Dislocation Mitigation in Monolithic GaAsP/Si Tandem Solar Cells

This work explores epitaxially integrated distributed Bragg reflectors (DBR) as a strategy to mitigate the impact of threading dislocations on the performance of monolithic GaAs0.75P0.25/Si tandem solar cells. The constraints present because of materials availability and the optical transmission profile of the GaAs0.75P0.25 top cell require the use of an enhanced bandwidth DBR design achieved by combining two narrow-band DBRs with different central wavelengths. The impact of this DBR structure on JSC, along with the competing effects of threading dislocation density (TDD), is investigated using a robust, experimentally informed analytical model. Implementing this DBR within the GaAs0.75P0.25/Si tandem cell structure is predicted to yield a short-circuit current enhancement equivalent to the ~1.8× reduction in TDD, providing a clear demonstration of its promise as a design methodology for mitigating the impact of non-negligible defect populations.