Multifunctional Cyanuric Fluoride‐Mediated Crystallization and Defect Passivation for 2D Sn‐Based Perovskite Thin‐Film Transistors

ABSTRACT Tin (Sn)‐based halide perovskites are promising for the semiconductor layer of thin‐film transistors (TFTs) owing to their intrinsic p‐type conductivity and environmental friendliness relative to lead‐based counterparts. However, Sn 2+ oxidation, poor film morphology, and high defect density severely limit their performance. Herein, cyanuric fluoride (Cy‐F), a multifunctional additive, is introduced into 2D phenylethylamine iodide (PEA 2 SnI 4 ) to improve film quality and device performance. Cy‐F strongly interacts with PEA + and Sn 2+ , enhancing PEA + anchoring, suppressing Sn 2+ oxidation, reducing pinholes, and passivating defects, thus forming uniform, well‐oriented films. With optimized 12 vol% Cy‐F doping, the TFT achieves a mobility of 1.88 cm 2 V −1 s −1 (more than one order higher than the pristine device's 0.15 cm 2 V −1 s −1 ). Concurrently, interface trap density decreases from 9.8 × 10 12 to 1.8 × 10 12 cm −2 eV −1 , significantly reducing the sweep hysteresis. Operational stability tests show the doped TFT retains 90% of initial drain current under negative bias stress for over 2000 s, with noticeable current recovery later. This work demonstrates Cy‐F as an effective additive for optimizing film morphology and charge transport, offering a new strategy for high‐performance, stable Sn‐based perovskite TFTs.