Face-on crystallization in ambipolar organic mixed conductors enables homogeneous light-modulated artificial neurons

Light-modulated artificial neurons are vital for clinical optic nerve repair and bionic robotics. Light-sensitive ambipolar organic mixed ionic-electronic conductors (OMIECs) allow for homogeneously integrated artificial neurons, free from issues such as voltage/resistance mismatch or digital-to-analog conversion. However, their development is constrained by a trade-off between ion and electron transport, which results in low figure-of-merit (μC*) values and P/N-mode imbalance. Here, through precise molecular weight tailoring, we develop an ambipolar OMIEC with a high face-on orientation ratio of 85.5% and a 4-fold enhancement in backbone crystallinity. This approach simultaneously enhances vertical ionic transport and electron transport, enabling the synergetic optimization of electronic mobility and volumetric capacitance. The optimized material achieves high μC* values of 423.3 ± 17.3 F cm^-1 V^-1 s^-1 (N-type) and 359.8 ± 42.6 F cm^-1 V^-1 s^-1 (P-type). Using this OMIEC, we construct a homogeneous artificial neuron whose excitation/inhibition behaviors can be dually modulated by light and chemical environment, paving new paths for high-performance OMIECs in biological neural prosthetics and bionic machine vision systems.