The study presented in this thesis provides details regarding the synthesis and characterization of different redox active molecules which can be applied to form the active layer of photovoltaic devices. For example in chapter two, star-shaped thiophene based molecules are described and their electronic and optical properties have been investigated. In chapter three, oligomers featuring bipyridinium units with different thienyl moieties have been successfully synthesized. Preliminary electropolymerization studies are achieved. In chapter four, two different series of powerful push-pull systems containing dimethyaniline DMA moieties as a strong donating group and TCNE or TCNQ as electron accepting groups have been prepared. These series feature quinone and oligothiophene units as supporting acceptor and donor unit. In chapter five, two different series of powerful organic dyes that could improve the efficiency of DSSCs by modulating the absorption of light towards the near-IR region are achieved. The influence of π-conjugated spacers on the optical and physical properties of synthesized dyes has been investigated. Preliminary DSSCs have been fabricated from some of these systems and their properties have been compared to dye N719
