Perovskite solar cells (PSCs) have made significant strides in efficiency, buttheir long-term stability remains a challenge. While external encapsulationmitigates extrinsic degradation and lead leakage, it does not fully addressperformance decline due to ion migration within the perovskite devices.Therefore, an internal encapsulation layer that can selectively transport chargecarriers and suppress ion migration across the interface is of greatsignificance for achieving long-term stability in these devices. Here,polytetrafluoroethylene (PTFE) can serve as an effective internal encapsulationlayer between the perovskite film and the electron transport layer in theinverted PSCs is demonstrated. The PTFE layer can selectively transportelectrons and suppress ion diffusion, resulting in a higher power conversionefficiency (PCE) of 25.49% compared to 24.74% of the control devices andmuch better long-term stability. Even after 1500 h of air exposure, the internalencapsulated perovskite devices can maintain 92.6% of their original PCE,outperforming the control devices at 80.4%. This approach offers a novelsolution for addressing ion migration-induced instability in perovskite devices.