Enolate‐Type Zwitterionic Passivator via Spiropyran Isomerization for Hole‐Conductor‐Free Carbon‐Electrode Perovskite Solar Cells

ABSTRACT The advancement of solution‐processable perovskite solar cells (PSCs) necessitates the effective management of defects generated during fabrication and operation via chemical passivation. Herein, an enolate‐type zwitterionic molecule, the open‐ring merocyanine (MC) isomer of 1,3,3‐trimethylindolino‐ β ‐naphthopyrylospiran (SPBenz), is used as a dynamic passivator. Upon exposure to polar solvents and sunlight, spiropyran‐type SPBenz undergoes a ring‐opening transformation to release its zwitterionic MC isomer. The oxygen atom in MC possesses a high electron density, enabling strong interactions with both the perovskite components and the underlying mesoporous TiO 2 electron transport layer. Concurrently, the zwitterionic MC passivates existing defects within the perovskite bulk and at the perovskite/TiO 2 interface while suppressing the formation of new defects during aging. The interaction also retards crystallization and optimizes the energy level alignment at the perovskite/TiO 2 interface, thereby facilitating efficient electron extraction. Benefiting from SPBenz incorporation, the power conversion efficiency of hole‐conductor‐free, fully printable mesoscopic carbon‐electrode PSCs increased from 19.10% to 21.86%. Furthermore, the SPBenz device retained approximately 90% of their initial efficiency after 570 h of maximum power point tracking under simulated 1‐sun illumination at 55°C ± 5°C.