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

Abstract 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 TiO ₂ interlayer strategy is introduced that fundamentally transforms the fabrication of Pb‐based MHP FETs. By pre‐depositing an ultrathin TiO ₂ layer before perovskite film deposition, reproducible and operationally stable MAPbI ₃ FETs with remarkable performance are achieved. Comprehensive characterizations reveal that the TiO ₂ 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 PDAPbI ₄ 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.