Living Passivation Strategy to Improve the Operational Stability of Perovskite Solar Cell

Organic-inorganic hybrid halide perovskites are the most promising next-generation photovoltaic material as single-junction perovskite solar cell (PSC) has reached over 25%, comparable with the main-market leader silicon. The next major challenge of PSCs, along with large-area processing and manufacturing upscaling, is improving their operational stability to reach similar lifetimes as silicon-based cells, because the perovskite absorber is sensitive to environmental factors (e.g., heat, water, and light) during manufacturing, storage, and operation. To fulfill this ambition, scientists have developed materials preventing the environmentalfactors to prolong the stability of perovskite and have achieved great improvement. Various passivation strategies, such as ionic liquids, lead oxysalt, self-assembled monolayer, 2D perovskite layer, have been developed to improve the performance and reliability. However, during PSC operation, the environmental stress factors will still promote the formation of new traps or charge carrier barriers within the perovskite absorber, which deteriorate device performance. All currently reported passivators are confined to protect certain locations after manufacturing stage, making it difficult to passivate newly generated defects during deviceoperation and storage.Ideally, the passivators not only protect defects during fabrication but also can be activated by stress factors to dynamically heal the perovskite absorber, thereby alleviating the instability problem during operation. Therefore, for the first time, this project proposes a ‘living passivator’ based on materials designed using dynamic covalent bonds, which can be triggered byenvironmental factors and then release additional passivators (e.g., Lewis bases) during operation, thus healing newly generated traps to ensure device operational stability. This idea is inspired by the concept of living polymerization, whose active site is kept dormant by adding Lewis acid or base during the polymerization, and re-activated by adding new monomers. It isalso similar to the sustained-release capsule in drugs, which continuously releases new chemicals to heal the specific tissue for a certain period to alleviate the detrimental effect. In this project, we believe that the proposed new idea of a real-time responsive passivation strategy for passivating perovskite films will open up a promising strategy with the potential to address the key challenge of long-term stability in the commercialization of PSCs.