Advanced Chemistry and Understanding of Acene-containing Conjugated Polymers for Functional Electronics PDF Download

Author: Ying Jiang
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Languages : en
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Book Description
Conjugated organic polymers and small molecules could potentially be employed as active material for high-throughput, low-cost and large-area device fabrication through solution processing. Electronic devices employing organic systems, such as organic light emitting diodes (OLEDs), organic photovoltaic cells (OPVCs) and organic thin-film transistors (OTFTs) for sensors and displays, have seen improved performances and commercialization in the recent decade. Continuous material innovation is the key towards the achievement of higher and better performances. Among various high-performing materials, large fused ring linear acenes, such as pentacene (Pn) and anthradithiophene (ADT) have maintained the benchmark for charge transport. Okamoto et al have since employed these structures into polymer backbones for solution-processable functional materials. This thesis explores in details the utility of Pn and ADT as building blocks in conjugated polymers. A variety of material and device characterization was carried out for the new materials developed. These include: (A) regio-regular Pn-containing copolymers. The direction of conjugation-extension (from 2,9- or 2,10-positions) was found to impact molecular order and charge-transport properties. (B) 2,8-conjugation-extended ADT-cyclopentadithiophene copolymers. Adjusting the bulkiness of the central substituents on the acene was found to impact molecular packing and charge-transport properties. Triisobutylethynyl-functionalized ADT achieved a photovoltaic power conversion efficiency of 2.7% in a polymer:fullerene bulk heterojunction device. (C) 5,11-conjugation-extended ADT copolymers. To explore impact on polymer electronic and packing behavior, ADT was incorporated with its long molecular axis orthogonal to the polymer backbone via in situ desilylation and Horner Emmons condensation. Using the first methodology, copolymerization with diketopyrrolopyrrole resulted in a low-bandgap polymer due to extended electron delocalization in the direction orthogonal to backbone. This polymer showed out-of-plane layered packing structure, and a high transistor hole mobility of 0.11 cm2 V-1 s-1. The second methodology enabled the development of an ADT monomer precursor exhibiting high ambient stability. Both 5,11-conjugation extended polymers yielded photovoltaic power conversion efficiencies of around 0.8 %. Through the development of these novel monomers and polymer, this thesis demonstrates the synthetic versatility that could be applied to pentacene and ADT in polymers, and the resulting ability to engineer the materials' energy levels and packing behavior. It shows that acene-containing polymers are promising materials for organic electronic devices.