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1
Tetrahedron Letters
Synthesis and characterization of three thienopyridazine-based copolymers and their
application in OFET
Chia Juan Lima,ɸ, Lu Lia,ɸ, Yanlian Leib, Feng Zhoud, Bo Wub, Xuyao Liua, Furong Zhub, Beng S. Ongc*,
Xiao Hud, Haibin Sud, Siu-Choon Nga*
aNanyang Technological University, School of Chemical & Biomedical Engineering, Division of Chemical and Biomolecular Engineering, 62 Nanyang Drive,
Singapore 637459.
bHong Kong Baptist University, Department of Physics, Kowloon Tong, Kowloon, Hong Kong SAR.
c Hong Kong Baptist University, Department of Chemistry, Research Centre of Excellence for Organic Electronics, and Institute of Creativity, Kowloon Tong,
Kowloon, Hong Kong SAR.
dNanyang Technological University, School of Material Science Engineering, Nanyang Avenue, Singapore 639798.
ɸBoth authors contributed equally to this work.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
Three low bandgap thienopyridazine-based donor-acceptor conjugated polymers,
PDTTPTT, PDTTPBT and PDTTPBDT were synthesized by Stille
copolymerization of thienopyridazine with thienothiophene, benzodithiophene
and bithiophene respectively. The optical band gaps of PDTTPTT, PDTTPBT and
PDTTPBDT polymers were determined as 1.41 eV, 1.43 eV and 1.58 eV
respectively by UV absorption. The deep HOMO level of the three polymers were
determined by cyclic voltammetry. The three polymers were fabricated to form
organic field-effect transistors and their performance as p-type semiconductors
were studied.
Available online
Keywords:
Pyridazine
OFET
Stille Coupling
Conjugated polymers
DFT
2009 Elsevier Ltd. All rights reserved.
allowed a significant increase in PCE by having a large D-A
interfacial area through an efficient interpenetrating network.
This concept marked a major breakthrough in this field and has
since been widely exploited.
1. Introduction
Organic photovoltaics have attracted tremendous interest in both
academia and industry due to the need for renewable and clean
energy.1 In particular, conjugated polymers have shown
enormous potential in various optoelectronic applications, such
as polymer solar cells (PSC), organic field-effect transistors
(OFET) as well as polymer light-emitting diodes (PLED).2
Polymeric semiconducting materials exhibit several advantages
in comparison to inorganic materials (e.g. Si) from the
perspective of low-cost, large scale processing, light weight and
chemical flexibility for modifications.3
During the development of organic photovoltaics (OPV) devices
with high power conversion efficiencies (PCE), Tang first
studied the concept of bi-layers which contained separate donor
and acceptor layers.4 However, this system displayed the
limitation of a small charge-generating interfacial area between
the donor-acceptor layers.5 Heeger and co-workers later reported
the construction of bulk-heterojunction solar cells, in which the
active layer was fabricated from a blended solution of donor and
acceptor materials using simple spin-coating.6 This system
An efficient OPV or OFET polymer should possess the following
physical and chemical properties: (1) high molecular weight; (2)
low band gap; (3) desirable HOMO and LUMO energy levels
(HOMO and LUMO should be tuned for considerations such as
stability, band gap, open circuit voltage and electron transfer); (4)
high charge carrier mobility; (5) favorable blend morphology; (6)
good solubility and processibility.7 The application of alternating
donor-acceptor systems (D-A polymer) has been an efficient
approach to tailor the HOMO-LUMO levels and band gap of
copolymers.8 To this end, a large amount of study has been
focused on developing and combining various building blocks to
prepare high performance D-A polymers.9-12
Acceptors based on thieno[3,4-b]pyrazine have emerged as an
important class of building blocks for the construction of low
band gap (LBG) polymers. Compared to poly(thianaphthene),
thienopyrazine exhibits more effective π-conjugation by having
two sp2-hybridized nitrogens to reduce steric strain.13