Performance Enhancement of Lead-Free 2D Tin Halide Perovskite Transistors by Surface Passivation and Its Impact on Non-Volatile Photomemory Characteristics

Two-dimensional (2D) tin (Sn)-based perovskites have recently received increasing research attention for perovskite transistor application. Although some progress is made, Sn-based perovskites have long suffered from easy oxidation from Sn²⁺ to Sn⁴⁺, leading to undesirable p-doping and instability. In this study, it is demonstrated that surface passivation by phenethylammonium iodide (PEAI) and 4-fluorophenethylammonium iodide (FPEAI) effectively passivates surface defects in 2D phenethylammonium tin iodide (PEA₂SnI₄) films, increases the grain size by surface recrystallization, and p-dopes the PEA₂SnI₄ film to form a better energy-level alignment with the electrodes and promote charge transport properties. As a result, the passivated devices exhibit better ambient and gate bias stability, improved photo-response, and higher mobility, for example, 2.96 cm² V⁻¹ s⁻¹ for the FPEAI-passivated films—four times higher than the control film (0.76 cm² V⁻¹ s⁻¹). In addition, these perovskite transistors display non-volatile photomemory characteristics and are used as perovskite-transistor-based memories. Although the reduction of surface defects in perovskite films results in reduced charge retention time due to lower trap density, these passivated devices with better photoresponse and air stability show promise for future photomemory applications.