One-year outdoor testing reveals degradation paths in perovskite tandem solar cells

TL;DR

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Researchers conducted a one-year outdoor test on perovskite/perovskite/silicon triple-junction solar cells, observing a decline in efficiency from 17–18% to about 13–14%. The degradation was primarily due to interface and encapsulation issues, not intrinsic absorber instability.

Researchers from TNO and Fraunhofer ISE have reported a significant decline in the performance of triple-junction perovskite/silicon solar cells after one year of outdoor exposure, with efficiency dropping from around 17–18% to approximately 13–14%. This finding highlights the durability challenges facing perovskite tandem technologies in real-world conditions, which is critical for their commercial viability.

The study involved outdoor testing of monolithic triple-junction devices in Petten, the Netherlands, over a period of more than a year. The devices, measuring 1 cm × 1 cm, combined a silicon bottom cell with two stacked perovskite subcells, designed for high theoretical performance. Initial measurements showed efficiencies of 17–18%, but long-term monitoring revealed a two-stage degradation pattern. The first phase involved voltage loss, while the second phase was characterized by encapsulation delamination, leading to reduced current collection and light in-coupling. Microscopy analysis indicated that delamination occurred within the encapsulation layers rather than at the active junctions, suggesting mechanical or interlayer adhesion failures rather than moisture ingress. Further analysis showed that performance losses were mainly due to interface degradation, shunt pathways, and non-uniformities within the device stack, rather than intrinsic absorber instability. Indoor tests confirmed good stability under damp-heat conditions but revealed significant losses under thermal cycling and UV exposure, with UV causing up to 65% efficiency decline.

Implications for Long-Term Stability of Perovskite Tandem Cells

This study underscores the importance of addressing interface and encapsulation stability for the commercial deployment of perovskite tandem solar cells. While the materials show promising initial efficiencies, their long-term durability under outdoor conditions remains a challenge. The findings suggest that future research should focus on improving mechanical adhesion, interface engineering, and UV resistance to enhance device longevity, which is vital for the broader adoption of perovskite photovoltaics in the energy market.

Previous Stability Data and Development of Perovskite Technologies

Prior to this study, most stability data for perovskite solar cells were obtained under controlled indoor conditions, with limited real-world outdoor testing. Researchers have been working to improve stability through material and device engineering, but long-term outdoor performance data has been scarce. The recent publication provides one of the first detailed insights into how these devices perform over an extended period in natural environments, revealing specific failure modes that need to be addressed to achieve commercial viability.

“The samples achieved 80% of the initial power conversion efficiency after five months of outdoor operation, and 50% after seven months.”

— an anonymous researcher from the study

Remaining Questions on Long-Term Device Stability

It is not yet clear how these degradation mechanisms will evolve beyond the one-year mark or how different encapsulation or device architectures might mitigate these issues. The impact of environmental factors such as extreme weather conditions, dust, and pollution on long-term stability remains to be fully understood. Additionally, the effectiveness of new stabilization strategies under outdoor conditions is still under investigation.

Next Steps for Improving Perovskite Tandem Durability

Researchers plan to test modified device architectures with enhanced encapsulation and interface engineering to reduce delamination and interface degradation. Further outdoor testing, including in diverse climates, is expected to evaluate the durability of these improvements. Commercial developers and material scientists will likely focus on integrating these findings into next-generation devices to extend operational lifespans and improve stability under real-world conditions.

Key Questions

What are the main causes of degradation in these perovskite tandem cells?

The primary causes identified are interface-related losses, encapsulation delamination, and UV/thermal-induced degradation of transport layers, rather than intrinsic instability of the absorber materials.

How much efficiency was lost during the one-year outdoor test?

The devices’ efficiency declined from about 17–18% initially to approximately 13–14%, with a reduction of roughly 50% after seven months.

Are these findings applicable to other perovskite device architectures?

The study focused on a specific triple-junction design, so while the degradation mechanisms may be similar, further testing is needed to confirm applicability across different architectures.

What measures can improve the long-term stability of perovskite tandem solar cells?

Enhancing encapsulation, improving interface adhesion, and developing UV-resistant materials are promising strategies to extend device lifespan under outdoor conditions.

When can we expect commercially viable perovskite tandem solar modules?

Significant durability challenges remain, and further research and development are needed before these devices can be reliably deployed at scale in commercial settings.

Source: PV Magazine