Smart Passivation Materials with a Liquid Metal Microcapsule as Self‐Healing Conductors for Sustainable and Flexible Perovskite Solar Cells

The electrical repair of device circuits has been considered a main issue in the area of electronic packaging. Demand for self‐healing conductors as cost‐effective and promising materials for prolonging the durability of devices has increased. Recently, diverse designs of self‐healing and deformable circuits have been introduced in virtue of their high stretchability and conductivity. However, encapsulating a liquid metal with a polymer in a micro‐size container is essential for real applications. In this work, core–shell‐structured liquid metal microcapsules (LMCs, diameter = 2–10 µm) are synthesized via in situ polymerization of urea‐formaldehyde onto liquid metal colloids. Passivation films comprising LMC/polymer composites are simply prepared using phase separation between the capsules and the liquid prepolymer. Capsules ruptured by cutting or pressing release and transport liquid metal to the damaged sites, leading to effective recovery of electrical pathways. Such self‐healing of the metal contacts shows the high potential of LMCs for smart passivation of electronic devices. As an example, flexible perovskite solar cells incorporated with the passivation film demonstrate perfect recovery of the photovoltaic parameters immediately after cutting the metal contact, exhibiting a power conversion efficiency (PCE) retention of 99% relative to the initial value (PCE = 15.07%). Liquid metal microcapsules (LMCs) are prepared by in situ polymerization of urea‐formaldehyde. A flexible perovskite solar cell employing the passivation film made of LMCs exhibits an excellent recovery rate from mechanical damage, 99% of initial power conversion efficiencies.