Tuning the photocurrent responsive and resistive switching performances of stilbazolium/iodoargentate hybrids by modulating the aggregation mode among chromophores

Abstract

The study about the effect of the stacking mode on the photo/electrical performance of crystalline organic/inorganic hybrids will be beneficial for the design of new photo/electrically active materials. In this work, D–π–A stilbazolium-type chromophores bearing novel ortho-N-alkyl substituents were synthesized and incorporated with iodoargentates to generate three crystalline stilbazolium/iodoargentate hybrids, i.e., [(CMAMP)(Ag₂I₃)]_n (1), [(HMAMP)(Ag₂I₃)]_n (2), and [(HMAHP)₂(Ag₅I₇)]_n (3). When the substitutes on the amine group range from –C₂H₅CN (for CMAMP⁺) to –C₂H₅OH (for HMAMP⁺), the same (Ag₂I₃)_nⁿ⁻ anions will be produced, and the π⋯π stacking interactions among stilbazoliums will be observed from absence to presence (weak head-to-head H-aggregation). Furthermore, when the substituent on the ortho-N of pyridine was also set as –C₂H₅OH (for HMAHP⁺), more electron-rich (Ag₅I₇)_n²ⁿ⁻ anion can be generated, and strong head-to-tail H-aggregation among HMAHP⁺ cations will happen. The enhanced aggregation strengthening in 3 can lead to its larger blue-shift photoluminescence, higher photocurrent, and better resistive switching performance (much higher ON/OFF ratio of 4.51 × 10²). Their binary resistive switching mechanism can be explained as the SCLC model, and the better photo/electrical performances of 3 stem from its stronger head-to-tail H-aggregations, more negatively charged (Ag₅I₇)_n²ⁿ⁻ anion, and stronger (Ag₅I₇)_n²ⁿ⁻–HMAHP⁺ interaction. The highly delocalized π antibonding orbitals between the empty p-orbitals of ethylene in its LUMO of (HMAHP)₂²⁺ dimer of 3 also support this conclusion. The good structure–property correlation based on accurate structural information in these stilbazolium/iodoargentate hybrids will be beneficial for the design of next-generation memory devices.