Thanks to this approach, they successfully reported room-temperature n-channel operation, with a claimed electron mobility of 0.5 cm 2 V –1 s –1. A similar strategy was later proposed by Senanayak et al., (9,30,31) who investigated solution-processed MAPbI 3 FETs by adopting 500 μs-long gate pulses. (18) In their case, clear electronic transport owing to the field effect could be observed for temperatures as high as 220 K by applying gate voltage pulses lasting a few seconds. In order to allow the investigation of the electrical characteristics of polycrystalline perovskite FETs in the presence of such combined effects, Labram and co-workers were the first to adopt transient measurements, in particular, for the case of a model MAPbI 3 system. (13,14) All these aspects also play a relevant role in optoelectronic devices such as photovoltaic cells and light-emitting diodes.
(8,9) Field-effect measurements can contribute to the understanding of, for example, structure–transport property relationships, (10) electron–phonon coupling, (11) and the interplay of electronic and ionic transport, (12) typically related to a hysteretic behavior. While 3D perovskite FETs could be investigated as a possible new powerful candidate for low-cost, large-area, and flexible electronics, it is certainly a powerful platform to deepen the understanding of charge transport in semiconducting thin films. (7) in 1999 on two-dimensional perovskite FETs. (1,2) Owing to their outstanding properties, such as high charge carrier mobility, (3) long diffusion lengths, (4) ambipolar nature, (5,6) and solution processability, 3D perovskite semiconductors have raised renewed interest also for adoption in field-effect transistors (FETs) after the pioneering work by Kagan et al. Three-dimensional metal-halide perovskite semiconductors have shown tremendous performance in optoelectronic devices, with solar cells achieving laboratory power conversion efficiencies above 25%. This study reveals the dynamic nature of the field effect in solution-processed metal-halide perovskites and offers an investigation methodology useful to characterize charge carrier transport in such emerging semiconductors. We infer this behavior to the accumulation of ions at the grain boundaries, which hamper the transport of carriers across the FET channel. In this work, we study the time-dependent electrical characteristics of field-effect transistors based on the model methylammonium lead iodide semiconductor and observe the drastic variations in output current, and therefore of apparent charge carrier mobility, as a function of the applied gate pulse duration. Interestingly, the observation of field effect at room temperature in transistors based on solution-processed, polycrystalline, three-dimensional perovskite thin films has been elusive. Charge transport in three-dimensional metal-halide perovskite semiconductors is due to a complex combination of ionic and electronic contributions, and its study is particularly relevant in light of their successful applications in photovoltaics as well as other opto- and microelectronic applications.