First outdoor ageing campaign for tandem cells

With efficiency levels above 30%, silicon perovskite tandem cells (Si/PK) are most likely to be the next-generation photovoltaic technology. However, while their yields are impressive, their lifetime and stability are among the major challenges to be overcome on the road to market.

Monitoring behavior of solar cells over time, outdoor, as in the real world, is critical to understanding their stability. In a real-life environment, the cells are exposed to a unique combination of stresses due to day/night cycles, spectral variations, temperature changes and high moisture levels. The impact of these conditions on tandem stability is still not well understood, and stability has been shown to be highly dependent on the tandem cell architecture itself.

So far, very few entities have reported publicly on the outdoor stability of the Si/PK tandem technology [1-3].

As part of their collaboration, 3SUN and CEA have carried out their first outdoor ageing campaign on Si/PK cells. Such a campaign, which investigates various perovskite sub-cell architectures, helps to define possible routes for future developments in device architecture and to identify the most promising layers for stable Si/PK tandem cells.

The campaign was carried out on the new MPPT bench installed on the rooftop of INES in 2024. It allowed us to verify some of our development choices and provided valuable first insights for our future research:

- The encapsulation materials chosen protect the tandem cells from external conditions;

- The selective layers play an important role in stability;

- The reference perovskite layer developed by our teams shows a good stability compared with others tested in the same campaign.