Electron configurations at 3d orbital of metal ion determining charge transition process in memory devices

Abstract

Functional polymeric materials with electrical bi-stable states possess significant potential for high-density data storage due to their nanoscale memory site, threedimensional-stacking ability and intrinsic flexibility. Aromatic polyimides bearing donor-acceptor (D-A) skeleton could form charge transfer complex (CTC) under electrical field, leading to their feasibility as memory materials. Three novel porphyrinated polyimides DATPP-DSDA, Zn-DATPP-DSDA and Mn-DATPP-DSDA were designed and synthesized for information memory applications. Metal ions with different electron configurations at 3d orbital have a determining influence on memory behaviors of polyimides: nonvolatile write-once-read-many-times memory (WORM) for DATPP-DSDA, volatile static random access memory (SRAM) for Zn-DATPP-DSDA, but no memory performance for Mn-DATPP-DSDA. By comparing the contribution of orbital transition and hole-electron distribution of charge-transfer excited states, roles of metal ions in regulating memory types were discussed. Molecular simulation results indicate that Zn ion could play a bridge role in paving the route for excited electrons from a D to A, while a trap role for Mn ion in hindering this process. This study proves the feasibility of the strategy for modulating the memory behaviors of porphyrinated polyimides by varying the central metal ion and provides the exact effects of various metal ions on regulating charge transfer processes.

Effect of a “Zn Bridge” on the Consecutively Tunable Retention Characteristics of Volatile Random Access Memory Materials

“…Obviously, with more Zn 2+ in co‐polyimides, the absorption intensities of peaks at 553 and 596 nm are higher and the other two peaks get weaker. It is due to the symmetry of porphyrin is enhanced after the introduction of Zn 2+ , leading to the degeneracy of both frontier orbitals and excited states [14a] …”

“…The intensity of emission peak at about 605 nm is enhanced with the increase of Zn 2+ , indicating it is dominated by zinc porphyrin moieties of coPI−Zn x . Actually, the “zinc bridge” effect is considered to enhance the hybridization of local and charge transfer (HLCT) excitations of porphyrinated polyimides [14a] . Thus the emission peak at about 605 nm is red shifted in the solvent with bigger polarity due to its HLCT feature.…”

“…coPI−Zn20, coPI−Zn50 and coPI−Zn80 possess volatile SRAM memory behavior with longer retention time. It is demonstrated that the retention time could be continuously and precisely tuned from 20 (coPI−Zn5) to 420 seconds (Zn‐DATPP‐DSDA, [14a] i. e., coPI−Zn100) by only altering the content of Zn 2+ in porphyrinated co‐polyimides.…”

Porphyrin Acceptors Improve the Crystallization of Y6 and the Exciton Dissociation in Ternary Organic Solar Cells

“…Furthermore, the Zn 2+ ion can construct an effective channel for the fast transfer of electrons directly from the D-unit to the A-units under an external field. 26 These can have positive effects on the photovoltaic performance of organic solar cells. 27,28 The branched long alkyl side chains on the thiophene units can increase the porphyrins' solubility.…”

“…The Zn 2+ ion has up to 10 electrons in the 3d orbital, which facilitates the formation of π-feedback bonds and thus increases the electron density of the porphyrin as an electron donor to promote the charge transfer process. Furthermore, the Zn 2+ ion can construct an effective channel for the fast transfer of electrons directly from the D-unit to the A-units under an external field . These can have positive effects on the photovoltaic performance of organic solar cells. , The branched long alkyl side chains on the thiophene units can increase the porphyrins’ solubility.…”