Synthesis and Properties of Low Band Gap Organic Semiconductors for Solar Cell Applications

The development of new PV technology is essential with increasing consumption of fossil fuels and seems to be the only way to cover energy demand. The primary objective should be accomplished efficiency between cost and power conversion efficiency. Moreover, the applicability of new materials is primarily determined by their balanced electrical, thermal, physical and chemical properties. In this thesis, a new series of low band gap aromatic polyimides were successfully synthesized to be used in photovoltaic applications as next generation organic semiconductor material. To this purpose, chitosan biopolymer based two aromatic polyimide functionalized with commercially available perylene and naphthalene organic semiconductors and previously synthesized high molecular weight naphthalene based polyimide have been characterized in detail by studying their , photophysical, thermal and electrochemical properties through the data obtained from NMR, FTIR, GPC, UV-vis, Fluorescence, DSC, TGA and CV and SQWV. Incorporation of the hydrophobic chromophore units within the hydrophilic polymeric backbones yielded a network-like structure and maintained good solubility. The compounds showed extraordinary thermal stabilities and high molar absorption coefficients. They possessed excimer type emission and aggregation formation which confirmed the electroactive species both in ground and excited state. The products showed outstanding electrochemical stability and also undergoes only one reversible reduction and oxidation in solid state which make them candidate as Donor/Acceptor polymer for PV technology. Keywords: Perylene, Naphthalene, Donor/Acceptor Polymer, High Molar Absorptivity