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

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.