Interface Field‐Effect Passivation Enabled by Selectively Extruded Cations for Printable Mesoscopic Perovskite Solar Cells with Improved Performance

Mesoporous electron transport layer (ETL) in printable mesoscopic perovskite solar cells (p-MPSCs) enables rapid and selective extraction of photogenerated electrons and facilitates device fabrication without a hole transport layer (HTL). However, the inherent mesoporous architecture introduces abundant interfacial defects that promote undesired non-radiative recombination, limiting the power conversion efficiency (PCE). To address this challenge, an interface field-effect passivation strategy is implemented, leveraging spatially selective cation extrusion. By incorporating tetraphenylphosphonium cations, sterically bulky organic ions that migrate to the perovskite/ETL interface during crystallization, a robust interfacial electrostatic field is introduced. This field simultaneously suppresses the non-radiative recombination by inducing field-effect passivation and enhances the charge extraction through optimizing energy alignment. The synergistic effects yield a PCE enhancement from 19.4% to 21.0%. This work underscores the potential of cation-engineered interfacial fields to improve the performance of HTL-free carbon-electrode perovskite photovoltaics.