The porphyrin-based copolymer PZnTPP-SFX is designed and synthesized by alternating porphyrin and spiro[fluorene-9,9'-xanthene] via Suzuki copolymerization. A simple memristor structure of ITO/ZnTPP-SFX/AlO x /Al was fabricated by spin-coating process. The conventional synaptic plasticity is emulated using the single memristor including nonlinear transmission characteristics, spike-timing dependent plasticity and spike-rate dependent plasticity. New spike-voltage dependent plasticity is also found in the memristor which can selectively perform potentiation and depression behaviors at a unipolar voltage. Compared with the device performance of uncoordinated metalloporphyrin polymer, it was found that oxygen vacancies diffuse and migrate into PZnTPP-SFX layer with the assist of coordination metal. This study suggests that porphyrin-based polymers have great promise for synaptic simulation of artificial neural network.
Two novel fluorenyl-porphyrins 2Flu-TPP and 4Flu-TPP serving as charge trapping elements are designed and synthesized through BF3. Et2O catalyzed Friedel-Crafts reaction. With steric hindrance building blocks of fluorene units, 2Flu-TPP and 4Flu-TPP present highly nonplanar 3-dimensional structure, which could effectively inhibit molecular packing and intermolecular arrangement of porphyrins. As charge trapping elements, porphyrin groups provide the hole trapping sites, while fluorene units act as a hole blocking group to reduce the formation of leakage current paths. The pentacene-based organic field effect transistor memory devices based on 2Flu-TPP and 4Flu-TPP show memory windows of 48.93 and 49.20 V, respectively. The 2Flu-TPP device shows reliable endurance property with a large ON/OFF current ratio (1.1×10 7 ) and good charge retention time (2.41×10 5 after 2×10 3 s). This study suggests that porphyrin based steric hindrance small molecular elements have great promise for high-performance organic field effect transistor memory.
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