Recent Advances in GaAsP/Si Top Cell Enabling 27% Tandem Efficiency

Historically, the performance of monolithically-integrated GaAsP/Si tandem solar cells has been limited by the presence of elevated TDD in the GaAsP subcell. However, our recent development of low-TDD GaAsP/Si virtual substrates has greatly improved the near-term potential for achieving high efficiency devices. In this work, development efforts employing this new low-TDD platform will be presented. First, our current certified record GaAsP/Si tandem cell (23.4% AM1.5G) is briefly analyzed, identifying the root cause of critical fill factor losses, which in turn informs subsequent design and optimization efforts. Second, the experimental development of high performance GaAsP subcells is shown, following device design strategies that improve J
SC
and fill factor without sacrificing V
OC
. Finally, conversion efficiency projections demonstrate that the achieved top cell performance metrics, combined with those expected from the newest bottom cell iteration, should enable ~27% efficient tandems.