Initiating Strain Field for Mitigating Lead Leakage in Perovskite Solar Cells with Built‐in Encapsulating Networks

Abstract Despite the remarkable power conversion efficiency (PCE) of perovskite solar cells (PSCs), their unsatisfactory operational stability and lead (Pb) leakage remain major obstacles to commercialization. Nevertheless, with the Pb precipitation mechanism remaining elusive, the community has long been under the impression that preventing Pb leakage mainly lies in the out‐film encapsulation. Here, that in‐film reinforcement is demonstrated through the synergy of built‐in chemical sealing networks encapsulating and balanced compressive strain field plays a pivotal role in elevating the thermodynamic barrier for structural dissociation, thereby preventing Pb leakage from severely damaged devices exposed to external stimuli. Through in situ planar‐resolved cathodoluminescence and depth‐resolved grazing‐incidence wide‐angle scattering, the spatial evolution of secondary Pb phases is further elucidated within the perovskite films. Consequently, a remarkable 96.98% inhibition rate for Pb leakage from damaged PSCs is achieved. Furthermore, the impressive PCEs of 26.11% in a cell (0.10 cm 2 ) and 20.41% in a module (100 cm 2 ) are achieved. More importantly, the unencapsulated PSCs maintain 97.05% of their initial PCE over 2160 h under humidity ambient. This work highlights the conceptual insights into mitigating Pb leakage by controlling in‐film structural rigidity, thus paving the way for the environmental sustainability of PSCs.