Syntheses, Morphology, and Properties of New Conjugated Polymers for High Performance Field Effect Transistors and Solar Cell Applications
Date Issued
2011
Date
2011
Author(s)
Lin, Hsiang-Wei
Abstract
Conjugated copolymers with well-ordered packing have attracted significant scientific interest recently due to their potential applications for high performance field-effect transistor and photovoltaic cells. In this thesis, we developed two new series of conjugated polymers to meet the above applications: (1) two-dimensional conjugated polythiophene with conjugated side chains; (2) selenophene based donor-acceptor conjugated polymers. The details of explorations are summarized as below:
1. Novel Two-Dimensional Quarterthiophene-Based Conjugated Polymers for Organic Field Effect Transistors and Photovoltaic Cells (Chapter 2): A series of new 4T-based polymers, including homopolymer poly(5,5’’’-di- (2-ethylhexyl)[2,3’;5’,2’’;4’’,2’’’] quarterthiophene) (P4T) and their copolymers P4TT, P4TSe, P4T2T, P4T2Se and P4TTT have been synthesized by Stille coupling reactions under microwave heating. The effects of their chemical structures on the electronic energy level, charge transport and photovoltaic properties were explored systematically. Among these copolymers, the field-effect transistor based on P4TTT showed the highest hole mobility of up to 0.396 cm2 V-1 s-1 due to its highly crystalline packing structure, and exhibited a high on/off ratio of 7.45×105, simultaneously. The performances of bulk heterojunction polymer solar cells based on the blends of these 4T-based polymers and 1-(3-methoxycarbonyl)-pyropyl-1-phenyl[6,6]C-71 (PC71BM) were also characterized. P4TSe/PC71BM based photovoltaic device showed the highest power conversion efficiency (PCE) of 2.60% under AM 1.5 illumination (100 mW/cm2). The above results exhibited that two-dimensional 4T-based conjugated copolymers could enhance the charge transport characteristics and emerge as a promising candidate for organic optoelectronic devices.
2. New Selenophene Donor-Acceptor Conjugated Polymer for High Performance Ambipolar Field Effect Transistor, and Solar Cell Applications (Chapter 3): A new conjugated copolymer PSeDPP from 2,5-bis-(trimethylstannyl)-selenophene(Se) and 3,6-bis-(5-bromo-thiophene-2-yl)-2,5-bis-(2-hexyldecyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione(DPP) was synthesized by Stille coupling reaction under microwave heating. The obtained polymer could form highly ordered lamella structure and π–π stacking after thermal annealing. Besides, the charge transporting characteristics of PSeDPP exhibited the relatively hole and electron mobility of up to 1.62 and 0.14 cm2 V-1s-1, respectively, which could store a large amount of charges to the memory device applications. On the other hand, PSeDPP based photovoltaic solar cells exhibited the best PCE of 1.64% with the blending weight ratio 1:2 for PSeDPP/PC71BM and 3vt% of 1,8-diiodooctane. The above results suggested that PSeDPP had potential applications for flexible electronics.
Subjects
Conjugated Polymer
Thin-Film Transistors
Photovoltaic Cells
SDGs
Type
thesis
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