Bulky side chain effect of poly(N-vinylcarbazole)-based stacked polymer electrets on device performance parameters of transistor memories

Three poly(N-vinylcarbazole) (PVK)-based polymer electrets were synthesized through Friedel-Crafts postfunctionalization for the function of charge storage in nonvolatile organic field effect transistor (OFET) memory devices. The bulky side chain effect of these stacked polymer electrets on the morphology, water contact angles, and memory characteristics were examined with regard to those of precursor PVK. The introduction of steric hindrance groups could interrupt the large length of π-stacked structures in PVK and block the form of region-regular structures from region-random on external electric field. As a result, the memories based on the three modified polymers exhibited approximate memory windows of 32 V increased by 13 V with respect to PVK. Besides, the write-read-erase-read cycles stability of the modified polymers was superior to that of PVK. Furthermore, we found that the holes were mainly located in the region of local π-stacked structures and bulky π-conjugated groups also acted as additional electron trapping sites. Molecular engineering of charge trapping site with tunneling polymers will be a promise strategy for the advance of transistor memory.