Theoretical studies of optical absorption in low-bandgap polymers

University essay from Institutionen för fysik, kemi och biologi

Author: Daniel Karlsson; [2005]

Keywords: ZINDO; Density functional theory; Hartree Fock method; Low bandgap polymers; Absorption spectra; Semi empirical methods; Plastic solar cells;

Abstract: The absorption spectra of a recently designed low-bandgap conjugated polymer has been studied using the semi-empirical method ZINDO and TDDFT/B3LYP/6-31G. The vertical excitation energies have been calculated for monomer up to hexamer. Two main absorption peaks can be seen, the one largest in wavelength corresponding to a HOMO to LUMO transition, and one involving higher order excitations. TDDFT results are red-shifted compared to the ZINDO results. Comparison with experiment yields that short conjugation lengths are dominating. This is possibly due to steric interactions between polymer chains, breaking the conjugation length. Such effects are also studied.

  AT THIS PAGE YOU CAN DOWNLOAD THE WHOLE ESSAY. (follow the link to the next page)