Optoelectronic synaptic devices, which integrate optical sensing and synaptic plasticity, are pivotal for emulating biological visual systems and advancing neuromorphic computing. Herein, we report versatile optoelectronic synapses based on SnO2/titanicone (Ti-based hydroquinone, Ti-HQ) heterojunctions fabricated via atomic/molecular layer deposition (ALD/MLD). The SnO2/Ti-HQ heterojunction structure introduces abundant charge trapping sites and a built-in electric field, significantly enhancing the optoelectronic response and relaxation time compared to a single inorganic SnO2 device. Importantly, this ALD/MLD-enabled optoelectronic heterojunction strategy exhibits general applicability and can be successfully extended to other metal oxide/metalcone systems. The SnO2/Ti-HQ device emulates a variety of synaptic behaviors, including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), transition from short-term plasticity (STP) to long-term plasticity (LTP), and the learning-forgetting-relearning process. The extremely low energy consumption per spike is confirmed in this device with ∼1.13 fJ at 0.1 mV ultralow bias voltage. Notably, the hybrid device also exhibits exceptional air stability, retaining 90% of initial EPSC after ambient storage for 9 months. Furthermore, optical logic operations and image preprocessing capabilities have been realized in the hybrid heterojunction devices. Its wavelength-dependent responses from ultraviolet to red light enable color discrimination. A proof-of-concept intelligent vehicle system, controlled by light wavelength, validates its potential for artificial vision. This work highlights a feasible and effective route for artificial optoelectronic synapses based on inorganic-organic hybrid heterojunctions by powerful ALD/MLD technology, showing enormous potentials in energy-efficient neuromorphic devices for multifunctional applications, especially in the biomimetic visual system.
Sun et al. (2026) studied this question.