Effect of Molecular Coplanarity on Resistive Switching Homogeneity of D-A Type Two-Dimensional Conjugated Polymers

Organic memristors have the advantages of ultra-fast speed, ultra-low power consumption, non-volatile storage, and low manufacturing costs, which are expected to become key electronic components to break through the von Neumann bottleneck and the limit of Moore’s Law. However, the stability, homogeneity, and repeatability of memristors prepared by organic materials are poorer than inorganic memristors. Most of the current research addresses this problem from the aspect of morphology and crystalline control, while the research on optimization at the molecular level is relatively poor. The molecular coplanarity can be effectively improved by using conjugated donor-acceptor units with strong push-pull electronic effects, functional groups with small steric effects and shorter alkyl chains. In this work, two novel two-dimensional conjugated donor-acceptor polymers, pBDTT-PTQx and pBDTT-BBT, were synthesized by the Stille coupling method, and their resistive switching properties were studied by optimizing molecular coplanarity. Both materials have highly robust Flash-like resistive switching behaviors and can be written and erased for more than 100 cycles. The simulation calculation of density functional theory shows that the resistance change mechanism of the two materials is charge transfer. Compared with pBDTT-PTQx, the dihedral angle between the donor and the acceptor of pBDTT-BBT is only −179.27 °, and the mean square roughness of the device surface is only 1.71 nm. The ON/OFF ratio of pBDTT-BBT can still be maintained at around 10 and the disturbance is small after the 10⁴ s read operation. What’s more, the disturbance coefficients of switching voltage are only 9.4% and 6.7%, and the disturbance coefficient of the resistance state is only 13.7% and 9.4%.