Control of effective conjugation length in polyfluorene thin films

The photoluminescence (PL) properties of polyfluorene thin films prepared by the spin-coating or drop-casting methods and subsequent thermal treatment have been systematically in vestigated. Depending oil the fabrication conditions, the emission photon energy of polyfluorene thin films varies from 2.81 to 2.92eV, and these thin films show that, as PL spectrum redshifts, PL quantum efficiency increases and sidebands in the PL spectrum are Suppressed. The changes are caused by the enhancement in transition dipole moment and the reduction in electron-phonon interaction, and that the results call be explained solely by the development of effective conjugation.