Halide perovskite photovoltaics is surging towards commercialization with the first industrially manufactured panels installed in the PV fields. With this, it is more important than ever for the researchers in the perovskite community to focus on identifying all the degradation and failure modes that could be triggered under real-world conditions to finding ways to overcome them.

In this contribution, we will share insights on the topic accumulated over the last 5 years of outdoor studies with perovskite solar cells exposed in Berlin, Germany. After testing a variety of perovskite absorbers, cell architectures and module encapsulation schemes, it is not surprising that we observed a host of different degradation pathways depending on the device architecture, including both extrinsic and intrinsic instability mechanisms [1]. Despite this, champion devices on our test field are already more than 4 years old providing an optimistic perspective of the possibility of reaching the desired operational lifetimes.

Severe failures occur if water vapour enters the device due to flaws in encapsulation. It results in different patterns of damage spreading depending on whether it originates from a specific weak spot (glass crack, imperfect adhesion of the edge sealant, etc.) or the overall high water vapour transmission rate of the encapsulation materials used. We also observe that encapsulation could be responsible for other degradation effects, such as layer delamination or chemical interaction between perovskite and encapsulation materials [2].

Intrinsic device stability, which is not related to the device encapsulation, is also critical. We confirmed such mechanisms as increased ionic losses under outdoor operation (due to electric field screening) [3], increased bulk defect concentration, localized phase segregation, and the formation of macroscopic defects. We also often see a change with ageing in the cell transient behaviour in the day-night cycle patterns. This constitutes another loss mechanism, often referred to as fatigue. Finally, we observed for a range of samples that the device layout can affect the ageing behaviour through various edge effects.

References

[1] S. Baumann, G. E. Eperon, A. Virtuani, Q. Jeangros, D.B. Kern, D. Barrit, J. Schall, W. Nie, G. Oreski, M. Khenkin, C. Ulbrich, R. Peibst, J. S. Stein, M. Köntges, Stability and reliability of perovskite containing solar cells and modules: degradation mechanisms and mitigation strategies. Energy Environ. Sci., 2024,17, 7566

[2] U. Erdil, M. Khenkin,* W. M. Bernardes de Araujo, Q. Emery, I. Lauermann, V. Paraskeva, M. Norton, S. Vediappan, D. K. Kumar, R. Kant Gupta, I. Visoly-Fisher, M. Hadjipanayi, G. E. Georghiou, R. Schlatmann, A. Abate, E. A. Katz, C. Ulbrich, Delamination of Perovskite Solar Cells in Thermal Cycling and Outdoor Tests. Energy Technol. 2024, 2401280

[3] S. Shah, F. Yang, E. Köhnen, E. Ugur, M. Khenkin, J. Thiesbrummel, B. Li, L. Holte, S. Berwig, F. Scherler, P. Forozi, J. Diekmann, F. Peña-Camargo, M. Remec, N. Kalasariya, E. Aydin, F. Lang, H. Snaith, D. Neher, S. De Wolf, C. Ulbrich, S. Albrecht, M. Stolterfoht, Impact of Ion Migration on the Performance and Stability of Perovskite-Based Tandem Solar Cells, Adv. Energy Mater. 2024, 2400720