Epitaxial Growth of Cs3Cu2I5 Single‐Crystal Arrays for UV‐Responsive Neuromorphic Devices

Copper‐based halides, a type of perovskite derivative, inherit their excellent optoelectronic properties and solution processability and also have the advantages of being nontoxic and stable. Despite the tremendous achievements of microfabrication in conventional halide perovskites, reports on copper‐based halide array devices are rare due to their difficult high‐quality crystallization. Here, by introducing single‐crystal thin films grown by space confinement method as substrates, reliable photolithography based on their single crystals is successfully achieved and controllable homoepitaxial single‐crystal arrays is demonstrated. By adjusting the substrate, angle, and growth time, the orientation, arrangement, and size of arrays could be controlled. Temperature and time are used to regulate the growth stage to obtain clean and appropriately sized arrays. ITO/Cs3Cu2I5/ITO neuromorphic device based on homoepitaxial arrays is developed. The variation of synaptic plasticity could be controlled by the number and frequency of light pulses. The device successfully simulated the process of “learning, forgetting, and relearning” in the human brain, demonstrating the potential of application in sensing‐storage‐computing‐integrated devices. Homoepitaxial Cs3Cu2I5 single‐crystal arrays are realized on Cs3Cu2I5 single‐crystal films by space confinement method (SCM). Highly repeatable growth of arrays are achieved with desired orientations, arrangements, and sizes by adjusting the substrates, directions of mask pattern, duration time of growth, and temperature of precursor solution.