Crosslinking and densification by plasma-enhanced molecular layer deposition for hermetic seal of flexible perovskite solar cells. (May 2023) - Wang, Zhenyu
Abstract: Flexible perovskite solar cells are new energy devices with a promising future due to their numerous advantages, such as high defect tolerance, strong solar absorption and low non-radiative carrier recombination rates. However, their operational stability is still an ongoing challenge during upgrading, and their inferior moisture corrosion resistance is still a major issue for better performances. Thin-film encapsulation could effectively enhance the operational stability of perovskite solar cells but obtaining encapsulation films with excellent barrier performance always come at the expense of poor flexibility. Therefore, the development of novel encapsulation materials with both barrier performance and flexibility is urgent for the compatibility of flexible applications. In this work, "Plasma-Enhanced Molecular Layer Deposition" was used for the first time to prepare a highly cross-linked, densified flexible encapsulation material AlOC at 40 ℃ to break through the traditional technology. The resulting encapsulation material can be applied to flexible perovskite solar cells as a barrier film without any damage. The as-obtained encapsulation film exhibited a water vapor transmittance rate of 1.44 × 10 −5 g m −2 day −1 and preserved 95 % of its initial barrier performance after 10, 000 bends with a 3 mm bend radius. Such performance was the best among the reported thin-film encapsulation layers of flexible perovskite solar cells. Graphical Abstract: O plasma is capable of oxidizing the unreacted active sites (-CH3 ) caused by steric hindrance and also creates active sites through the oxidation of H on the C backbone, which brings about densification and crosslinking of the barrier films grown by molecular layer deposition, resulting in an excellent barrier performance and flexibility. ga1 Highlights: The first proposal of plasma-enhanced molecular layer deposition, and its application in flexible PSCs encapsulation. First discovery of hydroxylation reaction of O plasma in molecular layer deposition. First study on the densification and crosslinking by O plasma. A water vapor transmittance rate of 1.44 × 10 −5 g m −2 day −1 and a bending radius limit of less than 3 mm were obtained. The encapsulated devices maintained 95 % of the initial efficiency after 2400 h under 30 °C and 80 % relative humidity.