The methylammonium tin iodide (MASnI \(_3\) ) thin-film transistor (TFT) still has key electrical performance problems such as threshold voltage drift and unstable mobility in practical applications. This is mainly due to the unreasonable distribution of defect density of states (DOS) caused by inherent defects in the material (such as tin vacancies). To address this deficiency, this paper proposes a novel bilayer MASnI \(_3\) TFT structure, which utilizes the interlayer chemical potential difference to suppress the formation of tin vacancies, thereby optimizing the defect density distribution to improve device performance. Based on the two-dimensional device simulator of TCAD, the influence of defect DOS parameters such as tail state-donor state, Gaussian-class dependent state on the electrical characteristics of the device was systematically studied. The simulation results show that, compared with the traditional single-layer structure, the bilayer MASnI \(_3\) TFT can adjust the threshold voltage to about 1 V and stabilize the saturation mobility at 11 cm \(^2\) /V \(\cdot\) s, providing a new structural optimization scheme for solving the performance bottleneck of tin-based perovskite TFT and offering theoretical guidance for the preparation of high-performance perovskite TFT.
