Radiating amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs) with deep ultraviolet light (λ = 175 nm) is found to induce rigid negative threshold-voltage shift, as well as a subthreshold hump and an increase in subthreshold-voltage slope. These changes are attributed to the photo creation and ionization of oxygen vacancy states (VO), which are confined mainly to the top surface of the a-IGZO film (backchannel). Photoionization of these states generates free electrons and the transition from the neutral to the ionized VO is accompanied by lattice relaxation, which raises the energy of the ionized VO. This and the possibility of atomic exchange with weakly bonded hydrogen leads to metastability of the ionized VO, consistent with the rigid threshold-voltage shift and increase in subthreshold-voltage slope. The hump is thus a manifestation of the highly conductive backchannel and its formation can be suppressed by reduction of the a-IGZO film thickness or application of a back bias after radiation. These results support photo creation and ionization of VO as the main cause of light instability in a-IGZO TFTs and provide some insights on how to minimize the effect.

Despite the widespread research on organic–inorganic hybrid perovskites, the ambient air instability and ion migration‐induced hysteresis in the current–voltage characteristics of their devices remain unsolved. Here, it is shown that stable ambient air operation of methylammonium lead iodide (MAPbI3) thin‐film transistors can be achieved by solution processing of the MAPbI3 film in ambient air via solvent engineering. N,N‐dimethylformamide (DMF), mixed with dimethyl sulfoxide (DMSO) and hydroiodic acid (HI), is found to be the most suitable solvent for one‐step deposition in ambient air. While the HI promotes homogeneous nucleation, the low boiling point of DMF and the high vapor pressure and strong Lewis base property of DMSO lead to fast crystallization and consequent large grain size. The oxygen in air passivates grain boundary defects, thereby improving lateral conduction and minimizing grain boundary defect‐mediated ion migration. This approach paves the way for the simple fabrication of hybrid perovskites by eliminating the need for well‐controlled inert environments and provides a solution for the problem of ambient air stability in perovskite devices.

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We exploit the problem of ion migration in the halide perovskite CH3NH3PbI3 (MAPbI3) by developing a memtransistor (i.e. hybrid memristor and transistor) with the field-effect transistor geometry. Application of an electric field between the drain and the source results in resistive switching from a high resistance state (HRS) to a low resistance state (LRS) due to dynamic redistribution of ions in the MAPbI3 layer. The gate enables continuous tuning of this LRS across several orders of magnitude. The LRS persists after removing the power supply and the memtransistor can be switched back to the HRS by reversing the bias polarity. Excellent state retention is demonstrated for 104 s and a switching ratio (HRS/LRS) of 102 is maintained for 1000 cycles, thus confirming good retention and cyclic endurance for the resistive switching behavior. Continuous tuning of the state conductance is essential for neuromorphic architectures and hard to achieve with two-terminal memristors.