Ultraweak light-modulated heterostructure with bidirectional photoresponse for static and dynamic image perception

The human visual system's adaptability to varying brightness levels has inspired the development of optoelectronic neuromorphic devices. However, achieving bidirectional photoresponse, essential for mimicking these functions, often requires high operation voltages or high light intensities. Here, we propose a bidirectional ZnO/CsPbBr3 heterostructure based neuromorphic image sensor array (10 × 10 pixels) capable of ultraweak light stimulation. The device demonstrates positive and negative photoconductivity through the ionization and deionization of oxygen vacancies in the ZnO channel, extendable to other ZnO/perovskites and IGZO/perovskites heterostructures. Operating at a reduced bias voltage of 2.0 V, the array achieves synaptic weight updates under green (525 nm) and UV (365 nm) light with light intensities ranging from as low as 45 nW/cm² to 15.69 mW/cm², mimicking basic synaptic functions and visual adaptation. It performs multiple image pre-processing tasks, including background denoising and encoding spatiotemporal motion, achieving 92% accuracy in pattern recognition and 100% accuracy in motion clustering. This straightforward strategy highlights a potential for intelligent visual systems capable of real-time image processing under low voltage and dark conditions. High voltages/light intensities are typically needed to mimic human visual adaptability. Here, the authors present an image sensor array with low operation voltage that mimics synaptic functions with ultraweak light stimulation and performs image processing tasks accurately.