Multifunctional Interfacial Layers from a One-Step Process for Effective Charge Capturing and Erasing in Low-Voltage-Driven Organic Thin-Film Transistors

The microstructure-dependent charge capturing and releasing behavior of dielectrics influences the memory characteristics of organic thin-film transistors (OTFTs). We use polyimide (PI) as the charge storage dielectric and incorporate an electron acceptor, namely, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), into PI through a simple one-step process to fabricate low-voltage-driven pentacene OTFT-based electrical programming/optical easing nonvolatile memories. Without the PCBM component, the OTFTs with the single-component PI layer exhibit almost no memory characteristics. After the incorporation of PCBM into the PI layer, the programming capacity of the OTFTs could reach 0.85 V at a low writing voltage of -3 V. Investigations on the microstructures and the impedance of the various PI layers indicate that the effect of phase separation coupled with PI dilution leads to the formation of an interfacial layer composed of thin PCBM regions and polar groups of PI between pentacene and PI layers. In the electrical programming process, the interfacial layer plays hole-capturing and -blocking roles to retain the programmed holes and achieve efficient hole programming. Under red-light irradiation, the pentacene and interfacial layers form a large p-n heterojunction area to provide electrons for recombination with the programmed holes, thereby achieving efficient hole erasure without applying any erasing voltage. Thus, low-voltage OTFT memory devices with nondestructive and energy-saving charge erasing can be realized. The discovered phenomenon can pave the way for the development of a highly efficient organic memory technology.