Sunlight, or solar energy, can play an active role in generating electricity and supplying global energy needs, as most renewable energy derives from the sun and can be utilized for a set of commercial or industrial applications. The use of this energy has been extensively studied using photovoltaic devices. Conjugated polymers can assist in utilizing sunlight for electronic applications. This area of research has recently become attractive to many researchers. In their attempts to shed light and develop efficient materials for use in this field, researchers have designed a number of different monomers that can be used either as donors or acceptors, and then copolymerised them using transition metal-catalysts to afford polymers with tailored properties for use in electronic devices.
In this thesis, efforts to design new generations of polymers for use in solar cells have involved thieno[3,4-c]pyrrole-4,6-dione (TPD) backbone as the acceptor unit in the alternating push-pull conjugated polymer, and included a variety of donor units (thiophene and fluorene) that couple in a similar fashion to those highlighted for P3HTs ([RIR] PTOP-TPDBP, [RIR] PTOP-TPDO, [RR] PTOP-TPDO, [T-T] PT2OP-TPDO, and [H-H] PT2OP-TPDO) and which use hydrophilic/hydrophobic substituents as side chains along the copolymer backbones (PFOXYDT-TPDOXY, PFOXYDT-TPDDMO, PFODT-TPDDMO, PFODT-TPDOXY, PTOXY-TPDOXY, PTOXY-TPDDMO, and PTODD-TPDDMO).
All copolymers were characterised using Proton Nuclear Magnetic Resonance, Gel Permeation Chromatography, UV-visible absorption spectroscopy, Cyclic Voltammetry, Thermal Gravimetric Analysis, and Powder X-Ray Diffraction. The optical properties were carefully studied and discussed. The optical band gaps of these copolymers were in the range of 1.80 eV to 2.12 eV. Thermal Gravimetric Analysis revealed that all the copolymers showed an excellent thermal stability. Powder X-Ray Diffraction studies indicated that the hydrophilic side chains promote a better chain packing of polymer chains with shorter interlayer distance than their alkylated counterparts.
