Meticulous Construction of Internal Encapsulation Layer via In Situ Self-Cross-Linking Polymerization and...

Capping an internal encapsulation layer (IEL) on the top surface of perovskite plays significant roles in enhancing perovskite quality and achieving high-performance perovskite solar cells. Herein, a novel IEL is in situ synthesized by self-cross-linking polymerization of siloxane motifs and ring-opening addition of ethylene oxide groups to overcome the long-overlooked drawbacks of IEL, such as eliminating deterioration influences of byproducts, as well as the tradeoff between improving perovskite quality and minimizing Pb²⁺ leakage. Comprehensive characterizations reveal that amidogen, hydroxyl, and carbon-fluorine (C─F) bond in GPTFP synergistically stabilize grain boundaries, passivate surface defects, block oxygen and moisture, as well as minimize the Pb²⁺ leakage of perovskite through hydrogen bond, oxygen-lead, fluorine-lead, and hydrophobic interactions. The resultant perovskite exhibits enhanced crystallinity quality, relieved residual strain, air-stable black phase retained after 200 days of ambient aging, and undetectable leakage of Pb²⁺ under simulated harsh conditions. Consequently, the resultant inverted device achieves an excellent efficiency of 26.83% (certified 26.57%) with a certified quasi-steady-state output of 26.51%. Notably, such a device retains >93 % of its initial efficiency after 2000 h of continuous 1-sun illumination (AM1.5G, 100 mW cm^-2) and 2000 h of ambient storage (30±5% relative humidity, 25 °C), respectively.