PHOTOLUMINESCENCE OF THIOPHENE-BASED COPOLYMERS WITH TUNABLE ENERGY-GAP

The photoluminescence spectra and the quantum yields of a series of co njugated polymers obtained by the copolymerisation of 3-butylthiophene and 3,4-dibutylthiophene in different ratio are reported. The emissio n maxima, like the absorption maxima, are tunable in the visible by va rying the fraction f of disubstituted monomers. By increasing f there is a blue shift of the spectra while the Stokes shift exhibits a consi derable increase both in the solid state and in solution. The role of ring rotations in the structural relaxation of the excited state and i n the non radiative recombination channels is discussed.