Enabling Robust N‐Type Perovskite Field‐Effect Transistors Through an TiO2 Interlayer Strategy

An ultrathin TiO2 interlayer strategy is developed for fabricating high‐performance, lead‐based, N‐type perovskite field‐effect transistors. This method improves film quality, reduces defects, and suppresses ion migration, enabling reproducible and stable devices. The strategy is successfully applied to both 3D (MAPbI3) and 2D Dion‐Jacobson phase perovskites, demonstrating its broad applicability and paving the way for perovskite‐based circuits. 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 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. An ultrathin TiO 2 interlayer strategy is developed for fabricating high-performance, lead-based, N-type perovskite field-effect transistors. This method improves film quality, reduces defects, and suppresses ion migration, enabling reproducible and stable devices. The strategy is successfully applied to both 3D (MAPbI 3 ) and 2D Dion-Jacobson phase perovskites, demonstrating its broad applicability and paving the way for perovskite-based circuits. 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. Advanced Science, Volume 12, Issue 48, December 29, 2025.