Solar cells based on organometal hybrid perovskites have exhibited promising commercialization potential owing to their high efficiency and low-cost manufacturing. However, the poor outdoor operational stability of perovskite solar cells restricted their practical application, and moisture permeation and organic compounds volatilization are realized as the main factors accelerating performance degradation. Herein, we developed a composite encapsulation, by sequentially depositing a compact Al2O3 layer and a hydrophobic 1H,1H,2H,2H-perfluorodecyltrichlorosilane layer on the completed device, to efficiently circumvent vapor permeability. Thus, the stability of the encapsulated perovskite solar cells was systematically investigated under simulated operational conditions. It was found that the MAPbI3 perovskite was prone to decay into solid PbI2 and organic vapor at high temperature or upon light illumination, and the decomposition was reversible in a well-encapsulated environment, resulting in reversible performance degradation and recovery. The enhanced thermal stability was ascribed to the competition between the perovskite decomposition and reverse synthesis. The as-prepared high-quality, multilayered encapsulation scheme demonstrated superior sealing property, and no obvious performance decline was observed when the device was stored under ambient air, continuous light illumination, double 85 condition (85 °C, 85% humidity), or even water immersion. Therefore, this work paves the way for a scalable and robust encapsulation strategy feasible to hybrid perovskite optoelectronics in a reproducible manner.
Keywords: atomic layer deposition; encapsulation; perovskite decomposition; perovskite solar cells; stability.