Comparison of two strategies to improve organic ternary memory performance: 3-Hexylthiophene linkage and fluorine substitution

In this paper, two acceptor-donor-acceptor (A-D-A) type organic small molecules, 4,4'-(5,5'-(benzo[c] [1,2,5]thiadiazole-4,7-diyl)bis(3-hexylthiophene-5,2-diyl))bis(N-(4-nitrophenyl)-N-phenylaniline) (NTPA 2 TBT) and 4,4'-(5,6-difluorobenzo[c] [1,2,5]thiadiazole-4,7-diyl)bis(N-(4-nitrophenyl)-N-phenylaniline) (NTPA 2 BTF 2 ), were synthesized and fabricated into resistive random access memory devices. Compared with our previously reported molecule NTPA 2 BT, NTPA 2 TBT has 3-hexylthiophene linkages bridging its donor and acceptor, while there are two additional fluorine atoms in the benzothiadiazole moiety for NTPA 2 BTF 2. Both the fabricated memory devices based on these two new molecules perform nonvolatile ternary memory characteristics with lower threshold voltages , higher reproducibility and better stability. The addition of 3-hexylthiophene bridges significantly promotes the planarity of the conjugation backbone and facilitates the molecular stacking, while the substitution hydrogen by fluorine improves the intermolecular interaction , and thus also induces an ordered molecular stacking. The insertion of 3-hexylthiophene bridges or fluorine atoms could be an effective strategy of tailoring organic molecules to improve data storage performance with lower power consumption.