Switching the resistive memory behavior from binary to ternary logic via subtle polymer donor and molecular acceptor design

Emerging organic resistive switching memory (ORSM) devices, in which active organic materials possess at least two stable resistance states have attracted considerable attention for their intriguing nonvolatile memory properties. Herein, solution-processed binary ORSM devices incorporating polymer donors (D) of poly(N-vinylcarbazole) (PVK) and small molecular acceptors (A) of 1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene (OXD-7) were first investigated. By varying the blending concentration of OXD-7, we demonstrated concentration-dependent resistance switching. To further mediate the memory characteristics, acceptors of both OXD-7 and butylphenyl-5-(4-biphenylyl)-1,3,4-oxadiazole (PBD) were incorporated into PVK donors to form a D–A–A system. The 6 wt% PBD-based ORSM device presented ternary resistive memory characteristics with well-separated current ratios of 1 : 10 : 10⁴ between “OFF”, “ON1” and “ON2” states, while three conductivity states held for 10⁴ s as a function of the time. To unveil the resistive switching mechanism of non-volatile memories, a detailed analysis of electrical properties and intertrap charge transfer in D–A and D–A–A systems was also performed.