Triggering WORM/SRAM Memory Conversion in a Porphyrinated Polyimide via Zn Complexation as the Internal Electrode

Abstract

We design two novel solution processable polyimides (PIs), NH-Por-6FDA and Zn-Por-6FDA, with 5,15-bis­(4,-aminophenyl)-10,20-diphenylporphyrin (trans-DATPP) (electron donor) and 4,4′-(hexafluoroisoprpoylidine)­diphthalic anhydride (6FDA) (electron acceptor) as the building blocks for polymer memory applications. The chemical structures of the two polymers are mostly identical with the only difference lying in the zinc ion (Zn2+) insertion into the porphyrin core in the Zn-Por-6FDA. Electrical characterization indicates that the NH-Por-6FDA possesses bidirectional nonvolatile write once read many times (WORM) memory behavior, while the Zn-Por-6FDA shows vastly different volatile static random access memory (SRAM) behavior. Both polymer memory devices show high ON/OFF current ratio up to 106 and exhibit excellent long-term operation stability in 108 read cycles and retention time of 4000 s with no current degradation. The charge transfer (CT) and function of the donor/acceptor moiety in the polymers related with the electrical switching effect are elucidated on the basis of optical, electrochemical measurement, and quantum simulation results. The inserted zinc ion in the porphyrin is suggested to form an internal electrode and act as a bridge during the electronic transition process, which facilitates both the CT and back CT, consequently triggering the WORM/SRAM conversion upon Zn complexation. The results observed here indicate the significance of metal-complexation on the memory effects, and will attract the attention of the researchers to use noble transition metals for the suitable expecting memory devices.

Metal-containing organic compounds for memory and data storage applications

“…To further explore the influence of Zn ion on the memory effect of porphyrinated PIs, Wu et al designed and synthesized a solution-processable Zn porphyrin-containing PIs with shorter spacer (P40). 160 It turned out that P40-based device showed the volatile SRAM-type memory behavior, while the counterpart without Zn element exhibited the non-volatile WORM-type memory character. This is because the metal ions are suggested to form an internal electrode and act as a bridge facilitating the CT process, consequently triggering the WORM/ SRAM conversion.…”

Synergy Effect of Porphyrin Units and Alkynyl π Bridges Tunes the Memory Behavior and Threshold Voltage of Hyperbranched Polyimides

“…Porphyrin and its derivatives possess large π conjugation systems and well-defined planar and electron-rich structures, which further makes them a kind of ideal electron donor material for next-generation memory devices. − Liou and Qi et al synthesized several novel porphyrin-based polyimides for memory devices. , The introduction of an appropriate π bridge into the conjugated backbone can generally optimize the performance of the memory device. On the one hand, compared with aromatic rings, the alkynyl has no side atoms that cause steric hindrance or atom repulsions.…”

“…22−25 Liou and Qi et al synthesized several novel porphyrin-based polyimides for memory devices. 26,27 The introduction of an appropriate π bridge into the conjugated backbone can generally optimize the performance of the memory device. On the one hand, compared with aromatic rings, the alkynyl has no side atoms that cause steric hindrance or atom repulsions.…”

Zinc Ion Triggered Controllable Binary/Ternary Memory Conversion Behaviors in Polyimides Containing Pendant Porphyrin Group

“…Based on these, four novel TPA‐based polyimides containing porphyrin pendant group, abbreviated as TPA(P)‐6FDA, TPA(ZnP)‐6FDA, TPA(P)‐DSDA, and TPA(ZnP)‐DSDA, were synthesized as memory materials based on charge‐transfer mechanism. In our previous work, [ 37 ] for memory porphyrinated polyimides, the central Zn ion in porphyrin ring could play a vital bridge role in enhancing the electron‐dragging ability of porphyrin moiety and promoting the transfer process of electrons between donor and acceptor moieties. So, we believed that in well‐conjugated TPA(ZnP) system the pendent Zn porphyrin is competitive with electron acceptor moiety and the “Zn bridge” effect could regulate the charge‐transfer process, which may endow polyimides with particular memory performance.…”