We have measured the time response of photoluminescence intensity in poly(di-(formula presented)-hexylsilane) films at 2 K with excitation densities from (formula presented) to (formula presented) excitons (formula presented) At the highest density, the photoluminescence has a rise time of 1.4 ps, which is ascribed to the exciton-exciton scattering time between initially photogenerated excitons. The inverse of rise times are sublinear to the excitation densities. The decay profiles are explained by the exciton-exciton annihilation with a rate constant of (formula presented) These processes are discussed in terms of exciton wave functions obtained by the one-dimensional Frenkel exciton model with disorder. We propose directional relaxation of excitons toward interacting points between different polymer chains as a mechanism for the efficient exciton-exciton annihilation.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2001|