Study of Electronic and Steric Effects of Different Substituents in Donor–Acceptor Molecules on Multilevel Organic Memory Data Storage Performance

Abstract

To study the influence of different types of substituent moieties onto the molecular backbones of conjugated donor–acceptor (D–A) molecules on the thin‐film morphology and performance of their memory devices, three new molecules X‐TBT were synthesized, which consist of the same backbone of two triphenylamine (T) groups and benzothiadiazole (BT) group, but have different substituents (X) with different electronic effects, that is, cyano group (CN), tert‐butyl group (tBu), and methoxy group (OMe). Nonvolatile ternary write‐once‐read‐many‐times (WORM) data storage behavior is achieved for the CN‐TBT and tBu‐TBT based devices as compared to the binary memory characteristic of TBT (X = H). In contrast, OMe‐TBT based device still maintains binary WORM behavior due to its unfavorable molecular packing motif and weak intermolecular charge transfer effect, but exhibits the lowest operating voltage (1.4 V) as a result of the lowest energy barrier between electrode and active layer. Notably, the tBu‐TBT based device displays the highest ION2/ION1/IOFF ratio of 107:103:1. Altering the substituents in D–A molecules can adjust the molecular packing, thin film morphology, and electron trap depth of the active layer, which then significantly influence the memory performance.

Improved Resistive Switching WORM Memory Behavior in D-π-A Architectures by Modifying the Terminal Donor Units

“…In addition, compound 9d with the tert -butylphenyl group exhibited a negative shift at 1.06 V due to the increased conjugation. Similarly, compound 9e with methoxyphenyl showed a shift at 0.78 V. The positive cathodic shift was observed in compounds 9b (−CHO) and 9c (−CN) due to electron-withdrawing groups in the TAA side arms . The quasi-reversible peak in the negative potential around −1.23 to −1.54 V corresponds to the BP unit .…”

“…The larger energy gap between the LUMO and Ag (−4.2 eV) electrode makes the process difficult to inject electrons from the electrode to LUMO upon a positive sweep. Consequently, the low injection barrier between the ITO and HOMO of compounds 9a – e ensures that the hole injection dominates the conduction process over the electron injection . Notably, compounds 9d and 9e exhibited a lower hole injection barrier of 0.66 and 0.38 eV, respectively; this phenomenon contributes to the lower threshold voltage of compounds 9d and 9e in memory performance.…”

Investigation of Dye Dopant Influence on Electrooptical and Morphology Properties of Polymeric Acceptor Matrix Dedicated for Ternary Organic Solar Cells

“…Surface sensitization dyes are standard process for DSSCs, the aim of this research is to investigate them in the context of applications in organic electronics, more specifically in organic photovoltaic cells. It is also required to consider their potential for use as colors controller in a polymer matrix [ 26 ], in organic transistors [ 27 ] or as organic memories [ 28 ].…”

Harnessing the Inductive Effect To Design New Donor–Acceptor–Acceptor′-Configured Small-Molecule Donors for Vacuum-Processed Organic Photovoltaics

“…In this regard, a vacuum-processed OPV device has been verified with superior stability recently, implying the bright prospect of SMOSCs . Many research efforts have endeavored to develop small molecules with various structural features that serve as electronic donors. , However, limited small molecules, instead of fullerenes, have been developed to work as electronic acceptors, leaving a prospective challenge of the material development to further improve the efficiency of SMOSCs. − Our designs of donor–acceptor–acceptor′ (D–A–A′)-configured small-molecule donors combining C 70 to serve as the active blends of vacuum-processed OPVs have successfully achieved high power conversion efficiency (PCE). − The dipolar character stemming from the asymmetric molecular structure leads to antiparallel dimeric packing motifs, which are beneficial for suppressing the bulk dipole to facilitate charge transport . The intramolecular charge transfer (ICT) feature of D–A–A′-configured molecules can be feasibly and/or systematically modulated by varying the electronic character of the constituting components D, A, and A′.…”

“…21 Many research efforts have endeavored to develop small molecules with various structural features that serve as electronic donors. 22,23 However, limited small molecules, instead of fullerenes, have been developed to work as electronic acceptors, leaving a prospective challenge of the material development to further improve the efficiency of SMOSCs. 24−27 Our designs of donor−acceptor−acceptor′ (D−A−A′)-configured small-molecule donors combining C 70 to serve as the active blends of vacuum-processed OPVs have successfully achieved high power conversion efficiency (PCE).…”