Enhanced Performance of Organic Field-Effect Transistor Memory by Hole-Barrier Modulation with an N-Type Organic Buffer Layer between Pentacene and Polymer Electret

Theoretical and experimental work has revealed that a positively charged insulator layer formed by oxygen-related defects near pentacene-dielectric interface in organic field-effect-transistors (OFETs) severely affects their performance. A novel OFET memory structure with an n-type organic buffer layer at the pentacene/polymer interface is proposed. In this structure, electrons are induced on the surface of the n-type organic layer near the interface due to the electrostatic field of the positively charged insulator and partly compensate the local positive charges at the interface, leading to a reduction in the height of hole barrier formed at the interface. On the other hand, the positive space charges will be induced in an extended region in n-type organic layer due to the limited density of ionized donors, blocking the back transfer of holes to pentacene as a result of the thicker positively charged layer. This idea is implemented in the n-type PTCDI-C-13-buffered OFETs with poly(2-vinyl naphthalene) (PVN) dielectric, in which greatly reduced P/E gate voltages, reliable P/E endurance of more than 10 000 cycles, and excellent retention time of more than 10(4) s with an I-ON/I-OFF of more than 10(4) under a set of P/E pulses with low amplitudes and short pulses are achieved in air.