Loss Analysis and Design Strategies Enabling >23% GaAsP/Si Tandem Solar Cells

Detailed loss analysis of our previously reported 21.8% (unverified) monolithic GaAsP/Si tandem cells has identified and quantified three main mechanisms limiting cell performance: dislocation mediated voltage and current losses, improper bandgap profile, and insufficient rear passivation. This analysis was recently used to redesign the device structure, yielding a substantial performance improvement to 23.4% AM1.5G. The largest area of improvement was in the Voc of 1.73V, an increase of 70 mV versus our previous results, enabled by an -2x reduction in threading dislocation density (TDD) and a more ideal top cell bandgap.