Highly Efficient n-Type Doped Single-Crystalline Perylene Diimide Microwires via Solution Processing for High-Performance Photosensors and Photo-Neuromorphic Devices

Solution-processed organic single-crystal semiconductors (OSCSs) with high charge transport properties are being actively studied. However, OSCSs show relatively low intrinsic conductivity in electronic devices compared to inorganic semiconductors. This problem can be solved through doping technology applied to OSCSs. In this study, the enhancement of conductivity and photosensitivity of n-type OSCS microwires (MWs) based on a small molecular semiconductor and an n-type organic cationic dye-based dopant is reported. Transmission and scanning electron microscopy show the attachment of n-type dopants to the terrace edge of OSCS MWs, enabling rapid electron transfer and strong interaction. The n-type doped OSCS MWs show enhanced conductivity and high optoelectronic properties, exhibiting 5,000 times improved photoresponsivity of 1.86 × 10⁴ A W⁻¹ compared to the OSC films fabricated by a thermal evaporation method. Furthermore, the fast photo-response time of n-type doped OSCS MW is measured to be 0.16 s. In addition, the high-performance photo-neuromorphic characteristics using the hole trap effect of cationic dye and applications including Pavlov's dog phenomenon showing conditioned reflex characteristics and image recognition using 4-bit reservoir encoding are demonstrated. The developed high-performance organic photoelectronic devices in this study can be utilized as essential components in future advanced artificial intelligence electronic devices applied to image sensing and optical communications.