Real-world climate conditions offer reality check for perovskite
Tandem perovskite/silicon solar cells perform only slight better than silicon-only cells in cloudy conditions in the Netherlands and the US, according to researchers from the AMOLF institute in Holland. However, adjustments including parasitic cell resistance, optical losses and nonradiative recombination in the tandem cells can boost efficiency by as much as 14 percentage points to above 38%
Research published by AMOLF has shown that in cloudy climates, such as that of northern Europe, tandem perovskite/silicon solar cells do not perform significantly better than standard silicon cells. The research also outlines a series of optimizations to improve perovskite quality, electrical contacts and light management, which could allow the cells to realize their potential and perform at much higher levels.

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.

Results showed that, even with cells rated at higher efficiencies, performance of tandem perovskite/silicon cells would only be marginally higher than that of the silicon cell alone, in the cloudy climates of the test locations in Utrecht, the Netherlands and Denver, USA.

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.

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“This has been a surprising finding,” states lead author of the study Moritz Futscher. “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, published in ACS Energy Letters, 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.

“Perovskite solar cells have shown breathtaking development in efficiency in recent years,” states the research publication. “Yet, our results highlight the need for a concerted effort in material development, device design and light management strategies to further increase the efficiency of perovskite cells, and develop highly efficient perovskite/Si tandem solar cells.”