Artificial short term synaptic behavior of organic polymer device capable of detecting both visible and infrared signals

Machine learning requires new materials and phenomena for the development of neuromorphic computing. Organic semiconductor (OSC) molecules and polymers are closer to the biological neural networks in the brain, hence their application can provide solutions to the limitations of conventional silicon technology in this field. This work proposes a two stimuli-based device that is capable of detecting the temperature difference due to the infrared wavelength between two electrodes and absorption of the photon by the active layer polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C14) which leads to a synaptic behavior. The combined optical and infrared wavelengths were acting as an external stimulus for the first-ever attempt to emulate multi-stimulus synaptic behavior. The total effect of the UV-Vis and infrared stimulus is responsible for the creation of excitons in OSC polymer and thermo-potential development across the two electrodes, respectively. This device shows synaptic behavior at a very low voltage of 70 µV. The device emulates the typical biological synapses like excitatory postsynaptic current (EPSC), pair-pulse facilitation (PPF), and short-term memory (STM). It also turns into an inhibitory postsynaptic mode from the excitatory mode upon applying the high external forward bias. The device has executed basic logic functions like “AND” and “OR” by applying external stimulation. The synaptic response due to the absorption of light by PBTTT-C14 with the add-on effect of the temperature difference between two electrodes shows a new direction in the artificial intelligence system capable of detecting both visible and infrared signals.