Formation of Hot Excitons, Annealing, and Relaxation in Conjugated Polymers under an External Optical Pulse

Abstract

With an optical pulse focusing on a typical semiconducting conjugated polymer, PPV, the resultant electron transition induces an oscillation of the band gap. The gap varies with a period of 50 fs and acts like a comb, filtering the original optical pulse to become an effective light pulse that has a period of 50 fs as well. The effective optical pulse thereby localizes the electron in the first 50 fs, yielding a hot exciton within 100 fs, which is in agreement with experimental results. Because of the prominent electron−lattice coupling of the conjugated polymer, the effective light field not only triggers lattice vibrations but also drives the hot exciton to undergo relaxation. During the relaxation over 1000 fs, the hot exciton loses its excess energy, finally completing its annealing process.