Encapsulation techniques play a crucial role in enhancing the longevity of perovskite-silicon tandem solar cells by protecting the sensitive perovskite layer from environmental degradation and mechanical stresses that can deteriorate performance over time.
Key Roles of Encapsulation in Perovskite-Silicon Tandems
Protection Against Moisture and Oxygen:
Perovskite materials are highly sensitive to moisture and oxygen, which can cause rapid degradation. Effective encapsulation forms a barrier that prevents ingress of water vapor and oxygen, thereby stabilizing the perovskite layer and prolonging device lifetime.
Thermal and Mechanical Stability:
Encapsulation materials need to accommodate the thermal expansion mismatch between inorganic solar cells and polymers to prevent mechanical stress and cracking during thermal cycling. Using elastomeric polymers like thermoplastic polyurethane (TPU) and thermoplastic polyolefin (TPO) with low modulus (~21 MPa) helps to minimize stresses on the cells, enhancing durability under temperature fluctuations encountered in real-world conditions.
Compatibility with Perovskite Chemistry and Processing:
Conventional encapsulants like ethylene vinyl acetate (EVA) are incompatible due to their hygroscopic nature and high lamination temperatures (>140 °C) that damage perovskites. Alternative encapsulants such as TPU and TPO are more suitable, being less hygroscopic and processable at lower temperatures, ensuring the chemical and structural integrity of the perovskite layer during encapsulation.
Optical Considerations:
Encapsulants influence the optical performance of tandem cells. TPU with UV-blocking additives reduces UV-induced degradation but can slightly reduce the current generation in the perovskite top cell due to absorption. TPO is more transparent in the UV range but absorbs slightly more in the visible spectrum. Both can improve visible light coupling and reduce reflection, positively affecting overall efficiency.
Long-Term Outdoor Stability:
Advanced encapsulation methods, especially those involving vacuum lamination and high-quality edge sealing, enable perovskite cells to pass stringent reliability tests such as IEC 61215 damp heat and thermal cycling. These methods have demonstrated retention of over 95% initial efficiency after prolonged exposure (e.g., >1566 h in damp heat and over 10 months outdoors), highlighting their importance for commercial viability.
Summary Table of Encapsulation Contributions
| Role | Effect on Perovskite-Silicon Tandems | Materials/Methods Involved |
|---|---|---|
| Moisture and oxygen barrier | Prevents degradation from environmental exposure | TPU, TPO, PIB tape, glass covers |
| Thermal/mechanical buffering | Reduces stress from thermal expansion mismatch | Low modulus elastomers (TPU, TPO) |
| Chemical compatibility | Avoids damage due to lamination temperature and reactions | TPU, TPO vs EVA |
| Optical transparency | Affects light absorption, current generation, and efficiency | Additives in TPU, choice of polymer |
| Long-term stability | Enables passing of accelerated tests and real-world durability | Vacuum lamination, edge sealants |
In conclusion, encapsulation techniques are essential to the durability and commercial deployment of perovskite-silicon tandem solar cells. By providing environmental protection, mechanical stability, chemical compatibility, and optimized optical properties, effective encapsulation significantly extends the operational lifespan and performance reliability of these high-efficiency tandem photovoltaics.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-role-do-encapsulation-techniques-play-in-enhancing-the-longevity-of-perovskite-silicon-tandem-cells/
