Synthesis and Properties of Donor-Acceptor Conjugated Macromolecules as N-Type Semiconductor for Organic Solar Cells

The fabrication of novel molecular dyes with suitable absorptive properties for photon harvesting is an essential area to search on for efficient photovoltaic cells. Perylene diimides show vibronic absorption band at the middle of visible region of solar irradiation. Introduction of substituents onto the perylene bay region usually perturbs the orbital energy of the perylene π-π intermolecular system which eventually leads to shifting of the absorption maximum to longer wavelength. In this thesis, the electrochemical properties of chiral multichromophoric macromolecule (NPM) and its components were well studied. NPM exhibited low band gap energies of 2.25 V and 1.7 V in solution and solid-state, respectively. Also, three novel macromolecular bay-substituted perylene diimides have been synthesized successfully and photophsically characterized namely, N,N'-Di(dodecyl)-1,7- diphenoxylperylene-3,4,9,10-tetracarboxy diimide (BP-PDD), N,N'-Di(5-amino-3- pyrimidinethiol)-1,7-diphenoxyperylene-3,4,9,10-tetracarboxy diimide (BP-PPD) and N,N'-Di(2,2,4(2,4,4)-trimethyl-6-aminohexyl))-1,7-di(1-amino-4- ethanolpiperidyl)perylene-3,4,9,10-diimide (TPE-PDI). All the synthesized compounds possess appreciable longer wavelength comparing them with their parent perylene diimides with good solubility in several organic solvents. These compounds were characterized in detail by several techniques such as NMR, FT-IR, Elemental analysis; UV-visible, Fluorescence, TGA thermogram, DSC and the results were analyzed. These results showed an asset for construction of photovoltaic devices such as organic solar cells. Keywords: Perylene, bay-substitution, absorptivity, macromolecule, solar cell