Eco-Friendly and Efficient Semi-Natural Encapsulants Prepared via In Situ Cross-Linking within the Porous Carbon Electrodes of Carbon-Based Perovskite Solar Cells

Abstract

The penetration of moisture and oxygen through the porous carbon electrodes of carbon-based perovskite solar cells (CPSCs) accelerates device degradation, thereby reducing their operational lifespan. To mitigate this issue, polymer encapsulation has emerged as an effective strategy to minimize moisture and oxygen penetration. However, commonly used epoxy-based encapsulants suffer from significant drawbacks, including inadequate toughness and the release of toxic gases during combustion. In this work, we developed an encapsulation process to incorporate eco-friendly and efficient encapsulants derived from cross-linked seminatural polymers into CPSCs. Optically transparent films of the encapsulants were fabricated by infiltrating precursor solutions containing hydroxy-terminated isoprene oligomers (HIO) and 1,6-diazidohexane (DAH) into the CPSC electrodes. The precursors underwent in situ cross-linking via thermal treatment, forming a durable HIO–DAH network both within and on the surface of the electrodes. By optimizing the mole ratios of the precursors, the resulting HIO–DAH film exhibited excellent thermal stability, a smooth surface, and exceptional water resistance. Consequently, CPSCs encapsulated with the HIO–DAH film demonstrated significantly enhanced stability under dark (70% relative humidity and 30 °C) and illuminated (70% relative humidity, 60 °C heating, and prolonged light exposure exceeding 900 h) conditions, compared to unencapsulated CPSCs and those encapsulated with commercial epoxy films. Moreover, the thermal degradation of the HIO–DAH film in an oxygen atmosphere at temperatures between 200 and 600 °C resulted in considerably lower emissions of toxic gases, including carbon monoxide (CO) and carbon dioxide (CO₂), compared to the epoxy films.