Enabling Robust N‐Type Perovskite Field‐Effect Transistors Through an TiO ₂ Interlayer Strategy

Metal halide perovskites (MHPs) show tremendous potential for field-effect transistors (FETs), but N-type Pbbased MHP FETs have been hindered by critical challenges, including high defect densities, ion migration, and poor reproducibility. In this work, a simple yet powerful ultrathin TiO₂ interlayer strategy is introduced that fundamentally transforms the fabrication of Pb-based MHP FETs. By pre-depositing an ultrathin TiO₂ layer before perovskite film deposition, reproducible and operationally stable MAPbI₃ FETs with remarkable performance are achieved. Comprehensive characterizations reveal that the TiO₂ interlayer enhances precursor wetting, promotes larger and more uniform grain formation, reduces defect density, and effectively suppresses non-radiative recombination and ion migration. The universality of this approach is demonstrated by successfully extending it to 2D Dion-Jacobson phase perovskites, including PDAPbI₄ and its derivatives. The fabricated devices exhibit excellent electrical characteristics, including high on/off ratios, low hysteresis, and impressive stability. As a proof of concept, a complementary inverter is constructed using perovskite-only components, showcasing the potential for integrated logic circuits. This work provides a robust fabrication method for high-performance Pb-based perovskite FETs with broad applicability.