Stress-relieving interface enabled by interlocking ionic polycarbolong for efficient and stable inverted perovskite solar cells

Fullerene (C₆₀) is a widely used electron transport layer in inverted perovskite solar cells, yet it faces a critical challenge: optically and thermally induced agglomeration that causes electrical losses in devices. Herein, we develop a corrugated polycarbolong interlocking (CPI) strategy to stabilize the perovskite/C₆₀ interface. The bidirectional coordination motifs of polycarbolong promote uniform C₆₀ deposition and enhance resistance to environmental stress. Its acceptor-π-acceptor-donor framework features triphenylphosphine-based “claws” that strongly anchor C₆₀, while terminal substituents passivate undercoordinated lead-ion sites. Leveraging the CPI strategy, the devices attain a high power conversion efficiency (PCE) of 27.43% and demonstrate remarkable stability under standardized protocols. Unencapsulated devices retain 94.8% and 95.6% of their initial PCEs after 2,200 h under continuous 85°C heating and 1-sun illumination, respectively. Furthermore, the encapsulated devices maintain 92.1% of their original PCE after 1,000 h of damp-heat testing.