Optical loss analysis of four-terminal GaAs/Si tandem solar cells

In this paper, we present a loss analysis for an in-house fabricated 4-terminal GaAs/Si tandem solar cell with a conversion efficiency of 21.3%. Current losses are broken down into ten loss channels and quantified. In order to predict the current gains from individual improvements, we set each parameter associated with one of the loss channels to its ideal value while keeping the other parameters constant. Using this loss analysis, the three most impactful losses, namely top cell metal grid reflection (3.40 mA/cm
²
), top cell window collection (2.06 mA/cm
²
) and reflection of the non-ideal antireflection coatings (1.96 mA/cm
²
), are identified and further optimization steps for the cell are suggested.