Defect‑anchored dipole molecules induce surface polarization facilitating high‑performance inverted perovskite solar cells

As inverted perovskite solar cells (PSCs) approach commercial viability, interfacial losses at the perovskite/charge transport layer junctions remain a critical bottleneck, causing severe carrier recombination and energy misalignment. Now, researchers from Huaqiao University and Lingnan Normal University, led by Professor Jihuai Wu and Professor Zhang Lan, have developed a novel surface polarization strategy that pushes device efficiency beyond 26% while dramatically enhancing operational stability.

Why This Interface Matters

Conventional surface passivation strategies often fail to simultaneously address defect-induced non-radiative recombination and interfacial energy level misalignment. The team ingeniously utilizes intrinsic surface defects—uncoordinated Pb²⁺ ions and halide vacancies—as anchoring sites for dipolar molecules, transforming these "flaws" into functional advantages for interfacial engineering.

Innovative Design and Mechanism

The researchers introduce 4-aminocyclohexanone hydrochloride (ACHCl), whose carbonyl groups coordinate with under-coordinated Pb²⁺ while chloride ions fill halide vacancies, synergistically passivating defects. Crucially, ACH⁺ cations anchor perpendicularly to the surface via these defects, forming an ordered cation-dipole layer with positively charged −NH₃⁺ groups oriented outward. This arrangement induces surface polarization, creating downward band bending that reduces the electron extraction barrier at the perovskite/PCBM interface while effectively blocking holes.

Outstanding Performance

The optimized devices achieve a champion power conversion efficiency of 26.12% (up from 23.98%), with an open-circuit voltage of 1.200 V and fill factor of 84.97%. The strategy reduces non-radiative recombination losses by 42 mV and enhances carrier extraction. Stability tests reveal exceptional durability: devices retain 91% of initial efficiency after 1,000 hours in ambient humidity and 92% after 1,000 hours under continuous illumination (ISOS-L-1I protocol), far surpassing the 50% retention of pristine devices.

Future Outlook

This work establishes a dual-functional strategy that converts surface defects into anchoring points for ordered dipole formation, simultaneously passivating traps and optimizing energy alignment. The approach offers a versatile pathway for developing highly efficient and stable inverted PSCs suitable for next-generation photovoltaics.

Stay tuned for more breakthrough research from this innovative team!