Exciton spectroscopy of red polydiacetylene chains in single crystals

The absorption and emission properties of excitons are investigated in a pure ‘red’ phase of luminescent polydiacetylene wires. The values of the binding energy (Eb = 0.556 eV) and Bohr radius (r ∼ 14 Å) make the ‘red’ exciton similar to the one of the extensively studied ‘blue’ phase, so the conformational modifications which lead to a reordering of excited states and luminescent emission do not strongly affect the exciton structure. The opening of a thermally activated non radiative channel leads to an efficient quenching of the intense luminescence observed at low temperature.