Enhancing the Electrical Characteristics of Organic Transistor-type Memory Devices through Interfacial Charge-Transfer Mechanism and Molecular Nanostructure
Date Issued
2016
Date
2016
Author(s)
Lo, Chen-Tsyr
Abstract
Organic-field-effect-transistor (OFET) -type memory devices have been extensively studied due to their flexibility, scalability, and solution processability. Functional polymer containing semiconducting elements is considered as one of the most promising charge storage materials for organic field-effect transistors and organic-based memory devices, since it features a systematic route towards materials with novel architectures, functions, and physical properties. However, there is limited study on the correlations of the nanostructure and the electronic characteristic. In this thesis, we report the OFET memory devices using the dielectric layer of cross-linked core-shell block copolymers containing conjugating segments in the cores, and reveal the effect of both block composition and nanostructure on the memory characteristics. We further explored the random copolymers consisting of both pendant electron-donating and -withdrawing groups as charge storage layer in the OFET memory devices. In addition, for comparing with the synthetic polymer electrets, the solution-associated supramolecules are also applied in the OFET memory devices as charge storage dielectrics. The important discovery of this thesis was summarized in the follows. 1. Non-Volatile Field-Effect Transistor Memory Devices using Charge Storage Cross-Linked Core-Shell Nanoparticles as Polymer Electrets (Chapter 2): Solution processable cross-linked core-shell nanoparticles containing conjugated elements are firstly explored as charge storage materials for transistor-type (OFET) memories. These uniform nanoparticles containing cross-linked electron-donating or donor-acceptor cores presented efficient flash-type memory characteristics. The devices using donor-acceptor nanoparticles presented both electron- and hole-trapping abilities, along with the memory window of 38 V, the retention ability of over 10^4 s, and endurance of over 100 cycles. 2. Multilevel Non-Volatile Organic Transistor Memory Devices using Pendent Donor-Acceptor Random Copolymer Electrets (Chapter 3): Non-volatile transistor memories were fabricated using n-type semiconductor BPE-PTCDI and dielectric layer of non-conjugated random copolymers with pendant electron-donating 9-(4-vinylphenyl)carbazole (VPK) and electron-withdrawing 2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiazole (OXD) moieties. The pendent structure provided restricting regions with well-defined donor-acceptor interfaces, which is not happened in the case of PVPK/POXD polymer blend. The multilevel data storage and endurance characteristics obtained by applying different voltage pulses suggested that the devices using random copolymer P(VPKxOXDy) as electrets possessed ambipolar and controllable non-volatile flash-type memory behaviors even when the working voltage was as low as 10 V. 3. High-Performance Non-Volatile Transistor Memory Devices using Charge-Transfer Supramolecular Electrets (Chapter 4): Non-volatile OFET memory devices using charge-transfer (CT) supramolecules of poly(4-vinylpyridine) (P4VP) with two different chromophores, 3-(dicyanomethylidene)indan-1-one (1CN-IN) or 1,3-bis(dicyanomethylidene)indan (2CN-IN) were demonstrated. The intermolecular CT interaction effectively introduced the chromophores as charge trapping sites into the P4VP matrix, leading to a controllable flash-type memory behavior. The 2CN-IN with one more electron-withdrawing dicyanomethylene group, compared to 1CN-IN, provided a better electron-trapping ability and thus obtained a larger memory window. The device based on P4VP(2CN-IN)0.30 electret exhibited the largest memory window of 79 V with the excellent retention ability of up to 10^7 s and endurance of over 100 cycles. Our study demonstrated the significance of interfacial charge-transfer mechanism and molecular nanostructure on the charge transporting and memory characteristics for novel organic electronic devices.
Subjects
transistor-type memory
block copolymer
polymer electrets
nano floating gate
donor-acceptor
random copolymer
supramolecule
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-105-D00524020-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):0117fef3a1bb74f7a09c4a87d849d1c1