Preparation of Porphyrin-Modified Polyfluorene Functional Materials and Their Optoelectronic Properties

Neural synapse mimicry plays a crucial role in realizing efficient artificial neural networks, and finding suitable materials for synapse mimicry devices is critical. Among many alternative materials, organic polymers can be designed with different structures to modulate the electrical properties, thus attracting the attention of researchers. The redox property of metal porphyrin and the charge transport property of polyfluorene were bonded to the same molecule by Suzuki coupling. Then the porphyrin-containing polyfluorene functional material (PF-ZnPor) was obtained, which had good thermal stability and was soluble in polar solvents. The structure of polymers was verified by X-ray photoelectron spectroscopy (XPS), UV-visible absorption spectroscopy and steady-state fluorescence spectroscopy, and thermogravimetric analysis of their stability. Using PF-ZnPor as the active layer, devices with the structure of Al/PF-ZnPor/ITO by solution spin-coating were prepared and applied to synapse mimicry research. The devices successfully simulated the synaptic enhancement and inhibition, the learning behavior of the human-like brain of remembering-forgetting-remembering, and so on. The effect of different thicknesses of the active layer on the device performance was also investigated. The results show that the electrical performance of the devices diminishes with increasing thickness of the active layer film. The HOMO energy level, LUMO energy level, and electrostatic potential (ESP) surface of the basic unit of PF-ZnPor were simulated by density-functional theory (DFT). The theoretical validation is in agreement with the actual experimental results. This study provides a new idea for the design of organic polymer resistive change materials applied to synaptic bionic devices.