Enhanced ternary memory performances with high-temperature tolerance in AIE@PBI composites by tuning the azobenzol substituents on tetraphenylethylene

Abstract

The design of functional composites with desired film crystallinity and definite switching mechanism is the key to achieve high performance multilevel memorizers. Three aggregation-induced emission (AIE) molecules containing different azobenzol (Azo) groups on tetraphenylethylene (TPE) were synthesized and embedded into polybenzimidazole (PBI) to prepare AIE@PBI composites, which were further fabricated as FTO/TPE-Azo-n@PBI/Ag (n = 01, 02, 04) devices with well-defined crystalline characteristics. These devices can demonstrate clear ternary memory performances, among which TPE-Azo-04@PBI-based one exhibited the best performance with the current ratio of 1:104.2:106.7 for “OFF”, “ON1”, and “ON2” states. The ternary memory mechanism can be designed as the combination of aggregation-induced current/conductance (AIC) and packing conformational change-induced charge transfer in TPE-Azo-n, which were verified by UV–Vis, in-situ XRD, and single-crystal structural determinations and theoretical calculations. The trend of ternary memory performance improved by increasing Azo groups on TPE can be attributed to the larger steric hindrance due to the more Azo groups, which can inhibit their aggregations and packing conformational change in PBI-confined space. Specially, this kind of devices can present high-temperature tolerance of 350 °C. The verified mechanism in this work might provide a practicable model for the design of new high-density memorizers with good environmental tolerance. The current ratio of OFF/ON1/ON2 increases with the Azo.