High-performance lead-free two-dimensional perovskite photo transistors assisted by ferroelectric dielectrics

The purpose of this research was to understand the effect of a built-in ferroelectric field on the performance of two-dimensional (2D) lead-free perovskite material-based phototransistor applications. In this work, ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and two-dimensional (2D) lead-free perovskite ((C₆H₅C₂H₄NH₃)₂SnI₄) were utilized as a dielectric layer and a channel layer, respectively. We observed that large hysteresis was successfully eliminated in the transfer curve, as well as the subthreshold swing being significantly reduced by one order of magnitude after P(VDF-TrFE) was introduced as a dielectric layer. Under polarization "up" and "down" states, the device achieved a high photo-switching on/off ratio (>100) and a short photoresponse time (50 ms), respectively. In addition to that, the device also demonstrated a high responsivity of 14.57 A W^-1 and a high detectivity of 1.74 × 10¹² Jones under the polarization "up" state with an illumination intensity of 21 μW cm^-2. In addition, low temperature solution-processed P(VDF-TrFE) and (C₆H₅C₂H₄NH₃)₂SnI₄ (except for the contacts of Au electrodes) in this work are considered to be suitable and compatible for flexible-based phototransistor applications in the future.