A solvent-based surface cleaning and passivation technique for suppressing ionic defects in high-mobility perovskite field-effect transistors

Organometal halide perovskite semiconductors could potentially be used to create field-effect transistors (FETs) with high carrier mobilities. However, the performance of these transistors is currently limited by the migration of ionic surface defects. Here, we show that a surface cleaning and passivation technique, which is based on a sequence of three solution-based steps, can reduce the concentration of ionic surface defects in halide-based perovskites without perturbing the crystal lattice. The approach consists of an initial cleaning step using a polar/nonpolar solvent, a healing step to remove surface organic halide vacancies and a second cleaning step. The surface treatment is shown to restore clean, near hysteresis-free transistor operation, even if the perovskite films are formed under non-optimized conditions, and can improve room-temperature FET mobility by two to three orders of magnitude compared to untreated films. Our methylammonium lead iodide (MAPbI 3 ) FETs exhibit high n- and p-type mobilities of 3.0 cm 2 V −1 s −1 and 1.8 cm 2 V −1 s −1 , respectively, at 300 K, and higher values (9.2 cm 2 V −1 s −1 ; n-type) at 80 K. We also show that the approach can be used to transform PbI 2 single crystals into high-quality, two-dimensional perovskite single crystals.