Donor-acceptor (D−A) conjugated polymers have attracted a good deal of attention in recent years. In D−A
systems, the introduction of electron withdrawing groups reduces Eg by lowering the LUMO levels whereas, the
introduction of electron donating groups reduces Eg by raising the HOMO levels. Also, conjugated polymers with desired HOMO and LUMO energy levels could be obtained by the proper selection of donor and acceptor units. Because of this reason, D−A conjugated polymers are emerging as promising materials particularly for polymer light emitting diodes
(PLEDs) and polymer solar cells (PSCs).
We report the design and synthesis of four new narrow band gap donor-acceptor (D-A) conjugated polymers,
PTCNN, PTCNF, PTCNV and PTCNO, containing electron donating 3,4-didodecyloxythiophene and electron
accepting cyanovinylene units. The effects of further addition of electron donating and electron withdrawing groups to
the repeating unit of a D-A conjugated polymer (PTCNN) on its optical and electrochemical properties are discussed.
The studies revealed that the nature of D and A units as well as the extent of alternate D-A structure influences the
optical and the electrochemical properties of the polymers. All the polymers are thermally stable up to a temperature of
300 °C under nitrogen atmosphere. The electrochemical studies revealed that the polymers possess low-lying HOMO
energy levels and low-lying LUMO energy levels. In the UV-Vis absorption study, the polymer films displayed broad
absorption in the wavelength region of 400−700 nm. The polymers exhibited low optical band gaps in the range 1.70 −