Nonvolatile memory organic field effect transistor induced by the steric hindrance effects of organic molecules

We report a nonvolatile memory organic field effect transistor (OFET) using ambipolar organic molecules as nano-interfaced semiconductor materials. Newly synthesized push-pull organic molecules (PPOMs) containing triarylamine as an electron donating group, thiophene as a spacer, and malononitrile as an electron withdrawing group are proposed. The tilted PPOMs with side chains could control the charge trapping of the conducting channel formed between pentacene and PPOMs. Quantum chemical calculations were carried out to estimate the dihedral angle at the neutral and electron charged anion molecules and to explain the charging effects for the memory OFET performance (write-read-erase-read cycles). The charge mobilities of OFETs comprising the nano-interfaced PPOMs were affected by the dihedral angles derived from the steric hindrance of the bulky side chain of the spacer. The memory OTFT with higher dihedral angle material exhibited a wider memory window as well as reduced current flow. The memory OFET devices showed a memory window of -40 to +40 V, a memory ratio of 100 for ON'' to OFF'' currents, and long retention time for the nonvolatile memory.