Organic nonpolar nonvolatile resistive switching in poly(3,4-ethylene-dioxythiophene): Polystyrenesulfonate thin film

Advancements in organic nonvolatile memory devices

“…Single-layer devices using either small organic compounds or polymers have also been demonstrated. Small organic compounds include pentacene [26], codeposited Cu:TCNQ (TCNQ:7,7,8,8-tetracyanoquinoline) [34], Alq 3 [29,35], N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1, 1′-biphenyl)-4,4′-diamine (NPB) [36], oxotitanium phthalocyanine (TiOPc) [37], and the polymers of polyaniline (PANI) [30], 8-hydroxyquinoline (8HQ) [27], poly [3-(6-methoxyhexyl)thiophene] [31], tetrathiafulvalene (TTF), and [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) [23], poly(3,4-ethylene-dioxythiophene): polystyrenesulfonate (PEDOT:PSS) [38]. Based on the different materials, it is possible to divide existing organic memory devices into three categories: charge-transfer complex memory devices, metallic nanoparticle (NP) doped memory devices, and all organic system memory devices.…”

“…Memory effect has been demonstrated in many singlecomponent materials, such as pentacene [26], TiOPc [36], NPB [37], PEDOT:PSS [38], Alq 3 [56], and PVK [57]. In 2004, Tondelier et al [26] studied both the triple-layer and single-layer structures based on pentacene.…”

“…In 2005, Lai et al [57] fabricated a bistable memory device by spin-coating the PVK films. The PVK films exhibit good retention and a high ON/OFF resistance ratio of 10 4 , with the filament theory used [38] to elucidate the switching mechanism. Recently, our group proposed a resistive switching device with a single-layer PEDOT:PSS film as the active material.…”

Polythiophene-based materials for nonvolatile polymeric memory devices

“…However, the bipolar switching device always had lower turn-OFF current than the turn-ON CC (turn-OFF/ON maximum current ratio: 0.8-1.0), and the unipolar switching device had higher turn-OFF current than the turn-ON CC (turn-OFF/ON maximum current ratio: 1.3-1.6), which indicated that the switching from ON to OFF state in the bipolar devices was eventually caused by the amount of carrier injection into the PEDOT:PSS thin film and reduction of the current paths and the switching in the unipolar devices by a current that was much larger than the turn-ON CC flowing through the device and rupturing the current paths. Therefore, both the BE material and the current compliance played crucial roles in the switching behavior and characteristics.Bipolar and unipolar switching mechanism can basically be explained as the formation of current paths due to the redox behavior of the PEDOT:PSS film [66,68,69]. When a voltage is applied to the electrode, the PEDOT chains will be oxidized to PEDOT 1 chains by the injected carriers.…”

“…In the unipolar switching devices, the current flowing through the current path in the devices is increased beyond the CC when a voltage is applied with a maximum CC. Then, the current paths are ruptured by a very large turn-OFF current [69], and the devices switch from ON to OFF state.However, in some PEDOT:PSS-based devices, the memory mechanism was not ascribed to redox behavior of the PEDOT:PSS film. Typically in two-terminal configurations of Al/PEDOT:PSS (70 nm)/Al [71] and Al/PEDOT:PSS/Cu device [72], the bipolar switching was proposed to arise from metal filamentary switching.…”