Relaxation processes in electronic states of conjugated polymers studied via spectral hole-burning at low temperature

Persistent and transient hole-burning (HB) at 4.2 K have been applied to study the intrinsic properties of electronic excitations of a ladder type π-conjugated poly(para-phenylene) in solutions. A narrow spectral hole less than 1 meV wide has been detected. The dependencies of the HB efficiency on the burn dose and wavelength, on doping the samples by electron scavenger are interpreted in terms of a photo reaction related to the two-level systems – specific low energy excitations in amorphous materials. In transient HB an additional hole broadening was observed which stems from the triplet energy transfer under conditions of lack of correlation of site energies of the singlet and triplet states of chromophores.