The main challenges in the long-term stability of perovskite solar cells (PSCs) stem from intrinsic material instability and environmental sensitivity, which hinder their commercialization despite high power conversion efficiencies (up to 25.8%). Key factors contributing to instability include:
- Material Instability due to Weak Interactions: Perovskite materials often contain unstable elements that rely on weak interactions such as van der Waals forces, making the crystal lattice prone to degradation over time.
- Environmental Degradation: Prolonged exposure to sunlight, moisture, humidity, and temperature fluctuations significantly accelerate degradation processes. These environmental stressors cause chemical breakdown and physical damage to the perovskite layer and device interfaces.
- Chemical Instability from Device Components: Certain chemicals used in hole transport materials (HTMs) like corrosive or hygroscopic dopants can induce instability. For instance, lithium salts commonly used to enhance conductivity may contribute to degradation, whereas replacement with more stable compounds (e.g., spiro instead of LITFSI) has shown improvements.
- Fabrication-Related Issues: The fabrication process and device architecture strongly influence stability. Different fabrication techniques (spin coating, sequential deposition, vapor methods) and device configurations (regular vs. inverted structures, organic vs. inorganic materials) affect how well the perovskite films withstand operational stresses.
- Structural and Compositional Modifications Need: Researchers have tried structural modification of perovskite films and exploration of hydrophobic and doped HTMs to improve stability, yet balancing efficiency and longevity remains challenging. While some formulations with hydrophobic HTMs demonstrated excellent short-term stability, their efficiencies are often low.
In summary, the long-term stability challenges of PSCs arise from their intrinsic chemical and structural fragility, environmental vulnerability, and interactions with device layers and dopants. Addressing these requires careful material engineering, protective coatings, optimized fabrication methods, and alternative dopants and transport layers to achieve durable perovskite solar cells capable of commercial deployment.
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