Interchain excited states in annealed poly [2-methoxy-5-(2'-ethyl-hexyloxy)p-phenylene vinylene] films

The optical properties of poly [2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) are studied by examining and analyzing the photoluminescence, ultraviolet-visible absorption and Fourier transform infrared spectra of the polymer films annealed in nitrogen or air atmospheres at different temperatures. The PL peak positions of the annealed spin-coating films are red-shifted markedly because of polymer chain relaxation. The relative intensities of the PL shoulder at 640 nm in the annealed MEH-PPV films are increased with annealing temperature, indicating that thermal annealing facilitates the formation of interchain species. The interchain excited states can be regarded as excimers in the MEH-PPV films since there is an absence of a directly excitable absorption band in ground states. (c) 2006 Elsevier B.V. All rights reserved.