Recently, the organic electronic devices have been developed rapidly. With the development of artificial intelligence, the research community has been able to design artificial synapses to simulate the function of biological synapses and realize information processing and calculation. The organic electrochemical transistor (OECT) is a novel artificial electronic device, which regulates electrochemical doping in organic semiconductor channels by applying gate voltage, leading to high coupling between ions and electrons. This affects the current in the channel. In this review, we summarize the latest research progress regarding OECT-based artificial synapses and discuss the materials of organic semiconductor film and electrolyte, working mechanisms, and the applications in intelligent sensors, medical field, and flexible and wearable device. Furthermore, the problems faced by OECTs and their outlooks are analyzed.

The use of electronic devices to emulate the unique properties of biological synapses is regarded as the key for the development of the artificial intelligence era to replace the conventional von Neumann's computing systems. Nowadays, many electronic devices have been proposed to simulate synaptic functions. However, organic photonic synaptic transistors (OPSTs) arise as an ideal candidate due to their comparative advantages, including the facile preparation process, the easy integration, and the tunable optoelectronic properties than the other devices configurations. As a result, they have attracted tremendous attention. Along these lines, in this review, the structure, working principle and synaptic function of the OPSTs are introduced in detail, while several common channel materials and their working mechanism are listed. Finally, the latest progress in the related application fields is introduced, and the perspectives for the future development of photonic synaptic transistors.