A team of researchers at the Netherlands’ AMOLF institute has modelled the performance of tandem perovskite/silicon solar cells under real-world climate conditions, and found that the tandem cells are just a little more efficient than the Si cell alone in the cloudy climates of the test locations. The research shows, however, that if correctly optimized, this type of cell could perform at efficiency levels above 38%.

Discounting all parasitic absorption in the transparent contacts of the perovskite cell, say the researchers, the tandem cells exhibited efficiency advantages of between 1.8% and 3.3%, far less than expected under ideal conditions.

“This has been a surprising finding,” states lead author of the study. “We have always thought that tandem cells operate at lower efficiency under low light conditions, but we are surprised that the effect is this large".

The research also shows that tweaking factors such as the parasitic cell resistance, optical losses and nonradiative recombination could boost this efficiency by as much as 14%, including in cloudy or low light conditions.

The researchers developed a model to simulate state-of-the-art perovskite solar cells, by combining an optical model based on EQE measurements with an analytical electrical model based on current-voltage characteristics.