Optically tunable threshold switching and thermally activated transport in planar Ag/MAPbI3 thin single‐crystal devices

Halide perovskites have enabled major advances in optoelectronics, extending well beyond photovoltaics. Their mixed ionic-electronic conduction, once regarded as detrimental to device stability, is increasingly viewed as a functional degree of freedomfor memory and neuromorphic-inspired devices, especially when coupled to external stimuli such as light. Specifically, singlecrystals are attractive models because they suppress grain-boundary effects and microstructural disorder that can mask intrinsictransport and interfacial mechanisms in polycrystalline films. Here, we report the growth of thin methylammonium lead iodide(MAPbI 3 ) single crystals by a space-confined method and their integration into planar two-terminal devices with directly depositedAg contacts. At room temperature, the devices exhibit ultra-low dark currents (10−13 -10−12 A) and negligible hysteresis in thedark. Under illumination, the current increases due to photogeneration and the I-V characteristics develop a pronounced polarity-dependent hysteresis and a threshold-like transition between two conductance states. Temperature-dependent dark measurements(300–400 K) show thermionically activated, contact-influenced transport and a weakly varying normalized hysteresis metric.Together with the back-to-back Schottky-diode analysis and control devices using more inert contact materials, these resultssupport a transport model in which Ag/perovskite interfaces play a central role and the hysteretic response is influenced by coupledinterfacial and ionic processes.