Interface-oriented bridges toward efficient carbon-based perovskite solar cells

The perovskite/electron transport layer interface plays a critical role in perovskite solar cell (PSC) performance and stability. Here, we report potassium bisaccharate (PB) acting as a multifunctional interfacial chemical bridge at the interface between the electron transport layer and the perovskite layer on introducing it into a buried interface. The carboxyl group at one end of the molecule is anchored to the hydroxy-rich SnO₂ surface through covalent interactions, stabilizing its out-of-plane orientation, and the carboxyl group at the other end reduces non-radiative recombination by passivating the under-coordinated Pb²⁺ in the perovskite. Sum-frequency generation (SFG) spectra confirm out-of-plane orientations and optimize energy level alignment. Carbon-based PSCs treated with PB achieve a champion PCE of 19.69% (active area: 0.04 cm²) and retain 95.8% of their initial efficiency after 1200 h under ambient conditions. These results demonstrate PB as a promising buried interface modifier to enhance efficiency and long-term stability in carbon-based PSCs.