Extending the light response range of organic photoelectric synaptic transistors by p-doping†

Organic optoelectronic synaptic transistors show great promise as a platform for future artificial visual synapses and integrated computing-storage systems due to their biocompatibility and excellent flexibility. However, the light response range of current organic optoelectronic synaptic transistors is limited to the visible and near infrared (IR) spectrum because of the intrinsic light absorption properties of organic materials. Given the significant potential applications of the infrared (or short-wavelength infrared, SWIR) spectrum in artificial synapse development, there is an urgent need for simple and effective methods to extend the optoelectronic synaptic response into the short-wavelength IR range. Here, we present an organic field-effect transistor (OFET) that operates as an optoelectronic synaptic device, achieving a significantly broadened spectral response by utilizing a charge transfer complex composed of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane and poly(3-hexylthiophene-2,5-diyl). At the wavelength of 1550 nm, the device exhibits an impressive 7920% enhancement in light response. Our artificial synaptic device not only replicates typical synaptic activity and mimics the human brain's learning processes but also demonstrates capabilities in optical information sensing, processing, and array imaging. Notably, owing to the pyro-phototronic effect of the active layer excited at 1550 nm, the artificial synapse achieves ultra-low power (40 fJ) operation under extremely low bias (−85.2 μV), addressing the challenge of achieving reliable, light-modulated neuromorphic applications with low power consumption. This study presents a straightforward yet effective approach for advancing neuromorphic computing in the SWIR region.